Introduction

CHAPTER I

1.0. INTRODUCTION

Traditional aboriginal knowledge of plants is responsible for most of the

medicine and food used in modern society.1 Herbs have been used throughout time

as food and as a primary tool for maintaining health and aiding in the recovery of

disease.2 About 80% of the world population use plant based medicines3 and about

one third of the world countries depend on herbal medicines. Arthritis is leading

cause of disability in adults all over the world, limiting day-to-day activities for

billion of people. WHO reports that 1% of the world population is affected by

arthritis (from Greek arthro- joint and itis - inflammation).4 It is a joint disorder

featuring inflammation. Arthritis is frequently accompanied by joint pain, which is

referred to as arthralgia.

There are many types of arthritis which range from those related to wear and

tear of cartilage such as osteoarthritis to those associated with inflammation

resulting from an overactive immune system such as rheumatoid arthritis.5 The

causes of arthritis depend on the form of arthritis. Some of the leading causes

include injury leading to osteoarthritis, metabolic abnormalities such

as gout and pseudogout, hereditary factors, direct and indirect effect of infections

and autoimmune disorders such as rheumatoid arthritis and systemic lupus

erythematosus.6 They are similar in that they have a tendency to affect the joints,

muscles, ligaments, cartilage and tendons and many have the potential to affect other

internal body areas. A joint is where one bone moves on another bone. Ligaments

hold the two bones together.7 The ligaments are like elastic bands, while they keep

the bones in place the muscles relax or contract to make the joint move. Cartilage

covers the bone surface to stop the two bones from rubbing directly against each

other. The covering of cartilage allows the joint to work smoothly and painlessly.8 A

capsule surrounds the joint. The space within the joint and the joint cavity has the

synovial fluid. Synovial fluid nourishes the joint and the cartilage. The synovial

fluid is produced by the synovium (synovial membrane) which lines the joint

cavity.9 All types of arthritis results in chronic illness that requires long term

treatment.10

The major complaint by individuals who have arthritis is joint pain. Pain is

often a constant and may be localized to the joint affected. The arthritis pain is due

to inflammation that occurs around the joint, damage to the joint from disease, daily

wear and tear of joint, muscle strains caused by forceful movements against stiff

painful joints and fatigue.11

Fig. 1: Comparison between a normal joint and an arthritic joint

Rheumatoid arthritis (RA) is a systemic inflammatory disorder affecting the

diarthrodial joint. It is an autoimmune disease that affects mainly the synovial

membranes and articular structures and is characterized by chronic, systemic

inflammation involving multiple joints (Fig.: 1). Small joints in the hands and feet

are usually affected first, followed by the larger joints. Patients with RA have

periodic flare-ups that can lead to irreversible joint destruction. Systemic effects

may include damage to organs such as the heart and lungs.12

Approximately 1.3 million US adults have RA, with prevalence being 2 to 3

times higher in women than men. Although the cause of RA remains unknown,

genes appear to play a role in disease development. Environmental or hormonal

factors may be involved in perpetuating the inflammatory process and joint

destruction.13,14

It has societal effect in terms of cost, disability and lost productivity.

However, the pathogenesis of disease is not well understood. Efforts are made to

understand the cellular and molecular mechanism for the pathogenesis of RA.15

Inflammation is known to result in increased production of nitric oxide (NO) and

prostaglandins. Interaction between these two mediators may provide an additional

point of manipulation of the inflammatory response to prevent debilitating diseases

such as rheumatoid arthritis.16

Approximately 80 percent of people diagnosed with RA will suffer from

synovitis (inflammation of the soft synovial joint tissue), cartilage damage and

develop bone erosions within one year of diagnosis.17 Rheumatoid arthritis causes

significant loss in work productivity, with up to one-third of those diagnosed unable

to work within two years of the onset of RA.18

Traditional methods of diagnosing RA rely both on a physical examination

and on blood markers that differentiate RA from other autoimmune connective

tissue diseases. Research exploring the development of new blood markers shows

promise in providing additional blood tests to help diagnose RA earlier, before

symptoms appear; those diagnosed earlier could then be started on drug

therapies designed to halt or slow down debilitating disease effects.19

C-reactive protein (CRP) and the erythrocyte sedimentation rate (ESR) are

both acute-phase markers of inflammation that are sometimes used to monitor RA

disease activity. CRP is produced by the liver in response to tissue injury, infection

and inflammation.20 Levels increase during periods of heightened RA disease

activity, but elevations may also reflect inflammation due to other causes such as

infection or injury. The ESR typically rises 24 to 48 hours after an inflammatory

stimulus and returns to normal levels gradually thereafter. ESR measurement may

help to assess disease activity when other clinical and laboratory studies yield

equivocal results.21,22 (Table 1)

A complete blood count with white blood cell differential can help document

the mild anemia, leukocytosis and other hematologic abnormalities sometimes

associated with RA. Urine analysis typically yields normal results. Liver and kidney

function should be assessed before starting therapy with DMARDs to establish

baseline values and at intervals thereafter.23,24

Table 1. Tests Available to Support Diagnosis, Prognosis and Follow-up of

Rheumatoid Arthritis25,26

Assay Method Clinical Use

14-3-3 eta Protein ELISA Assist in diagnosis of RA

Rheumatoid Factor (RF) Latex agglutination/

immunoturbidimetry

Assist in diagnosis and determining

prognosis of RA; detects primarily IgM

RF

Rheumatoid Factor (IgA) ELISA

Provides added specificity when used in

combination with other RF or anti-CCP

assays; may help predict severity of

disease course

Rheumatoid Factor (IgG) ELISA

Provides added specificity when used in

combination with other RF or anti-CCP

assays

Rheumatoid Factor (IgA,

IgG, IgM)

ELISA

Assist in the diagnosis of RA; detecting

all 3 isotypes improves the specificity and

predictive value

Cyclic Citrullinated

Peptide (CCP) Antibody

(IgG)

ELISA

Assist in diagnosis and determining

prognosis of RA—more specific than RF

Rheumatoid Arthritis,

Diagnostic Panel

Includes RF and CCP

antibody (IgG).

Latex agglutination/

immunoturbidimetry

(RF)

ELISA (CCP

antibody)

Provides additional diagnostic and

prognostic value relative to assay alone

Rheumatoid Arthritis

Diagnostic Panel with

14-3-3 eta Protein

Includes rheumatoid

factor IgM, CCP IgG,

and 14-3-3 eta protein.

Latex agglutination/

immunoturbidimetry

(RF)

ELISA (CCP

antibody and 14-3-3

eta protein)

Provides additional diagnostic and

prognostic value relative to each assay

alone

Erythrocyte

Sedimentation Rate

(ESR)

Modified Westergren Assess disease activity

C-Reactive Protein

(CRP)

Nephelometry Assess disease activity

ELISA- Enzyme-Linked Immunosorbent Assay

Generally, NSAIDs and DMARDs are prescribed for rheumatoid arthritis,

these drugs have to be given for long periods; they accumulate in tissues produce

toxic effects such as retinal damage and corneal opacity and other effects like rashes,

irritable bowel syndrome, myopathy and neuropathy which can be minimized by

increasing bioavailability thereby lowering the dose of the drug.27

Treatment with disease-modifying anti-rheumatic drugs (DMARDs) can

often ameliorate the disease and improve the clinical outcome. Thus, therapy should

be initiated early in the course of the disease to minimize irreversible joint damage.28

In any oral allopathic dosage form the drug gets metabolised by first pass

metabolism and only the other reach the circulation.29 To increase the bioavailability

of such medicine an agent that can increase or enhance the drug bioavailability and

which can reduce the dose of drug is desired. Such an agent is called bioenhancer.30

A bioenhancer is an agent capable of enhancing bioavailability and efficacy

of a drug with which it is co-administered, without any pharmacological activity of

its own at therapeutic dose used.31 They tend to decrease the dose of active drug

required for the optimal endpoint of the treatment strategy, bypassing the need to use

injectable routes of drug administration to a larger extent, might help in overcoming

the resistance to antimicrobials and saving the precious raw materials for the

manufacturing of medicines. Such fixed drug combinations (FDCs) are

economically viable too.32

Both synthetic and herbal drugs face a problem of reduced bioavailability,

which is the rate and extent of drug entering systemic circulation and becomes

available at the site of action.33 Maximum bioavailability is attained by drugs

administered intravenously, whereas drugs administered orally usually undergo first

pass metabolism and are poorly bioavailable due to incomplete absorption. Such

drugs that have not been utilised by the body may lead to drug resistance and

adverse effects.34

The best way to achieve reduction in drug dosage, thereby drug toxicity and

cost is by increasing the drugs bioavailability.35 One of the ways of increasing the

bioavailability of drugs is by addition of molecules which do not have similar

therapeutic activity but increase the bioavailability when incorporated in the

formulation of another drug. These are called as bioenhancers and they do not show

synergistic effect with the drug.36

Modern researchers show increased interest in the enhancement of

bioavailability of most of the drugs by addition of various herbs with bioenhancing

property.37

To achieve bioenhancing property of a drug various approaches are adopted

for instance by using absorption enhancers, prodrugs, micronisation, manufacturing

of delayed release, sustained release capsules and spansules, permeability enhancing

dosage forms like liposomes and emulsions.38,39

1.1. AYURVEDA – YOGVAHI

In Ayurveda, the concept of bioenhancer is termed as Yogvahi. It is used to

enhance bioavailability, tissue distribution, increase efficacy of drugs especially

drugs with poor bioavailability. Specific yogvahis or bioenhancers are called as

Anupaan and Sehpaan.40,41

1.1.1. ANUPAAN

This means food concomitantly given with medicament to increase the effect

of medicament. For example: Amrit Dhara drops. It is used in gastrointestinal

diseases. These drops are taken after they are put with sugar to increase their

potency.

1.1.2. SEHPAAN

This means vehicle used during the manufacture of dosage forms to increase the

effect of the drug. For example: Panchgavya prepared using ghee or clarified butter

to increase its effect.

Examples of yogvahis generally used in ayurvedic formulations are Piper longum,

gold, cow urine distillate, etc.

1.2. PROPERTIES OF BIOENHANCER

The bioenhancers used in formulation should comply with the following

properties42 like

non-toxic

effective at very low concentration

easy to formulate

enhance the activity of the drug molecules

should not possess any pharmacological activity of its own at the therapeutic

dose used.

1.3. CLASSIFICATION

Bioenhancers are broadly classified43-45 depending on two parameters

1. Based on origin

2. Based on mechanism of action

1. Based on origin

This is further classified into plant and animal origin.

Few examples for plant origin: Stevia, Piperine, Capsaicin, Allicin, Ginger, etc.

An example for animal origin: Cow urine distillate.

2. Based on mechanism of action

Inhibitors of P-gp efflux pumps

Example: Carum carvi, Genistein, Sinomenine

Suppressors of Cyp -450 enzyme and its isoenzymes

Example: Naringin, Gallic acid, Quercetin

Regulators of GIT function to facilitate better absorption

Example: Aloes, Niaziridin, Ginger, Liquorice.

1.4. MECHANISM OF ACTION

There are several mechanisms of actions by which bioenhancers act.

Different bioenhancers have different or same mechanism of action.46-48

For example: Nutrition bioenhancers enhance absorption by acting on GIT.

Antimicrobial bioenhancers act on drug metabolism process.

Bioenhancing activity of herbal compounds is attributed to many

mechanisms, like inhibition activity of P-gp by flavone, quercetin and genistein,

inhibition of efflux transporters like P-gp and breast cancer resistance protein

(BCRP) using naringin and sinomenine thus preventing drug resistance; DNA

receptor binding, modulation of cell signaling transduction and inhibition of drug

efflux pumps by stimulating leucine amino peptidase and glycyl-glycine dipeptidase

activity thus, modulating the cell membrane dynamics related to passive transport

mechanism as seen with piperine; nonspecific mechanisms like increased blood

supply to the gastrointestinal tract, decreased hydrochloric acid secretion, preventing

breakdown of some drugs and inhibition of metabolic enzymes participating in the

biotransformation of drugs, thus preventing inactivation and elimination of drugs

and thereby increasing their bioavailability.

Other mechanisms of action postulated for herbal bioenhancers are as

follows:

(a) Reduction in hydrochloric acid secretion and increase in gastrointestinal blood

supply

(b) Inhibition of gastrointestinal transit, gastric emptying time and intestinal motility

(c) Modifications in GIT epithelial cell membrane permeability

(d) Cholagogous effect

(e) Bioenergetics and thermogenic properties

(f) Suppression of first pass metabolism thereby inhibition of drug metabolizing

enzymes and stimulation of gamma glutamyl transpeptidase (GGT) activity which

enhances uptake of amino acids.

1.5. BENEFITS

Use of bioenhancers poses the following benefits49 to the world population

Reduced drug dosage.

Reduced cost of drug.

Reduced resistance of drug.

Reduced adverse drug reaction or side effects.

Increased efficacy

Increased bioavailability

Decreases requirement of raw material for drug manufacture.

Economically benefitted to the world economy.

Decreases treatment cost.

1.6. HURDLES

Bioenhancers in drug delivery have been successful but not all the

approaches have been met with all success. The newly developed bioenhancers have

many challenges50 to be faced.

To improve the properties of drug formulation like circulation in blood

increased functional surface area, protection of drug from degradation,

crossing biological barriers & site specific targeting.

The research & development of herbal bioenhancers in large-scale

production is a problem. It is easy for pilot scale production than the large-

scale production.

The next posed problem is on regulatory control. There is a need to have

regulations for physicochemical & pharmacokinetic properties of newer

bioenhancers than the other conventional drug products.

Bioenhancers propose a newer concept in the discovery based on traditional

system of Indian medicine. The improvements in this concept will definitely lead to

reduction in cost of drug, toxicity and other adverse effects and will have a

beneficial influence on the economy of the country. It is safe, effective, economical,

easily procured too.

Thus, the approach of bioenhancer in modern medicine is very essential

today and the development of bioenhancers from other sources has become the need

of the hour.

1.7. DRUG ABSORPTION BARRIERS

The drug must cross the epithelial barrier of the intestinal mucosa for it to be

transported from the lumen of the gut into the systemic circulation and exert its

biological action (Fig.: 2).51 There are many anatomical and biological barriers for

the oral drug delivery system to penetrate the epithelial membrane. There are many

structures in the intestinal epithelium, which serve as barriers to the transfer of drugs

from the gastrointestinal tract to the systemic circulation. An aqueous stagnant layer

due its hydrophilic nature is a potential barrier to the absorption of drugs. The

membranes around cells are lipid bilayers containing protein such as receptors and

carrier molecules.52 Drugs cross the lipid membrane by passive diffusion or carrier-

mediated transport which involves the spending of energy. For the passage of small

water-soluble molecules such as ethanol there are aqueous channels within the

proteins. The drug molecules larger than about 0.4 nm face difficulty in passing

through these aqueous channels.

Recent work has shown that drug efflux pumps like P-gp possess very

important role inhibiting efficient drug entry into the systemic circulation. P-gp is a

type of ATPase and an energy dependent transmembrane drug efflux pump, which

belongs to members of ABC transporters. It has a molecular weight of 170 kDa and

has 1280 amino acid residues. Since P-gp is gaining importance in absorption

enhancement much work has still been made about its modulation due to its

substrate selectivity and distribution at the site of drug absorption.53

Fig. 2: Drug transport across membrane

1.8. METHODS IN USE FOR ENHANCEMENT OF ABSORPTION OF

ORALLY ADMINISTERED DRUGS

There have been many approaches in use to enhance the intestinal absorption

of poorly absorbed drugs. These approaches are as follows:

Absorption Enhancers: Many of the absorption enhancers54,55 are effective in

improving the intestinal absorption such as bile salts, surfactants, fatty acids,

chelating agents, salicylates and polymers. Chitosan, particularly trimethylated

chitosan increases the drug absorption via paracellular route by redistribution of the

cytoskeletal F-actin causing the opening of the tight junctions. Bile, bile salts and

fatty acids are surfactants which act as absorption enhancers by increasing the

solubility of hydrophobic drugs in the aqueous layer or by increasing the fluidity of

the apical and basolateral membranes. Calcium chelator such as EGTA and EDTA

enhances absorption by reducing the extracellular calcium concentration leading to

the disruption of cell-cell contacts.

Prodrugs: To enhance the drug absorption and bioavailability chemical

modification of drugs to produce prodrugs56 and more permeable analogues has

been widely studied as an useful approach. Various ampicillin derivatives are one of

the well-known examples of increasing the lipophilicity of agents to enhance

absorption of a polar drug by prodrug strategy. Ampicillin due to its hydrophilic

nature is only 30 - 40% absorbed from the gastrointestinal tract. By esterification of

carboxyl group of ampicillin the prodrugs of ampicillin such as pivampicillin,

bacampicillin and talampicillin were synthesized. These prodrugs were more

lipophilic than the parent compound following oral administration and they showed

higher bioavailability in comparison with ampicillin.

Dosage Form and other Pharmaceutical Approaches: Utilization of permeability-

enhancing dosage forms is one of the most practical approaches to improve the

intestinal absorption of poorly absorbed drugs. Various dosage formulations57 such

as liposomes and emulsions enhanced the intestinal absorption of insoluble drugs.

Particle size reduction such as micronization, nanoparticular carriers, complexation

and liquid crystalline phases also maximize drug absorption.

P-glycoprotein Inhibitors: The application of P-gp inhibitors in improving peroral

drug delivery has gained special interest. Several studies to enhance oral

bioavailability have demonstrated the possible use of P-gp inhibitors that reverse

P-gp-mediated efflux in an attempt to improve the efficiency of drug transport

across the epithelia.58 P-gp inhibitor influences absorption, distribution, metabolism

and elimination of P-gp substrates in the process of modulating pharmacokinetics.

1.9. MEDICINAL PLANTS AND THEIR COMPOUNDS AS DRUG

BIOAVAILABILITY ENHANCER

There are various plants and plant materials have been reported to be used as

bioavailability enhancer. Some of them are listed below.

Piperine: Piperine (1-piperoyl piperidine) is a pioneer alkaloidal component of

Piper nigrum Linn. or Piper longum Linn. Piperine, or mixtures containing piperine,

increases the bioavailability, blood levels and efficacy of a number of drugs

including ingredients of vasaka leaves, vasicine, sparteine, rifampicin, phenytoin,

sulfadiazine and propranolol.59,60

Ginger: Ginger (Zingiber officinale) has a powerful effect on GIT mucous

membrane. It regulates the intestinal function to facilitate absorption. Ginger is used

in the range of 10-30 mg/kg body weight as bioenhancer.61 The bioavailability of

different antibiotics like azithromycin (85%), erythromycin (105%), cephalexin

(85%), cefadroxil (65%), amoxycillin (90%) and cloxacillin (90%) are increased by

it.

Drumstick Pods (Moringa oleifera): Niaziridin, a nitrile glycoside is isolated from

the pods of Moringa oleifera which enhances bioactivity of commonly used

antibiotics against gram-positive bacteria like Myobacterium smegmatis, Bacillus

subtilis and gram-negative bacteria like Escherichia coli. It enhances activity of

rifampicin, ampicillin, nalidixic acid by 1.2 - 19 folds against the gram-positive

strains, also enhances the activity of azole antifungal drugs such as clotrimazole

against Candida albicans by 5 - 6 folds. It increases the absorption of Vitamin

B12.62

Liquorice (Glycyrrhiza glabra): Bioenhancing activity of liquorice is due to its

active component glycyrrhizin. It enhances cell division inhibitory activity of

anticancerous drug `Taxol` by 5 folds against the growth and multiplication of breast

cancer cell line. Inhibition of cancerous cell growth by taxol in presence of

glycyrrhizin was higher than treatment with taxol alone. It is reported that

glycyrrhizin enhances the transport of antibiotics like rifampicin, tetracycline,

nalidixic acid, ampicillin and vitamins B1 and B12 across the gut membrane. At the

same concentration, glycyrrhizin shows a more potent absorption enhancing activity

than caproic acid. Absorption enhancing activity obtained from the simultaneous

treatment of sodium deoxycholate and dipotassium-glycyyrhizin was much greater

than sodium deoxycholate alone in Caco-2 cell monolayers.63

Black cumin (Cuminum cyminum): Bioactive fraction of Cuminum cyminum

enhances the bioavailability of erythromycin, cephalexin, amoxycillin, fluconazole,

ketoconazole, zidovudine and 5-fluorouracil. The doses responsible for the

bioavailability enhancement activity ranged from 0.5 to 25 mg/kg body weight. It is

itself an effective gastric stimulant, carminative and anthelmintic. It has been used

therapeutically as an anti-diarrhoeal, galactagogue, diuretic and also beneficial in

hoarseness of voice. Bioavailability/bioefficacy activity of Cuminum cyminum64 was

attributed to various volatile oils, luteolin and other flavonoids.

Cumin/Caraway (Carum carvi): Seeds enhance the bioavailability of antibiotics,

antifungal, antiviral and anticancerous drugs. The effective dose for the Carum carvi

bioactive fraction as bioenhancer is in the range of 1-55 mg/kg body weight.65 They

have carminative, mild stomachic, aromatic and diuretic actions. It shows greater

bioenhancing effect when used in combination with bioenhancer from Zingiber

officinale and piperine.

Garlic (Allium sativum): Allicin, the active bioenhancer phytomolecule in garlic

enhances the fungicidal activity of amphotericin B against pathogenic fungi such as

Candida albicans, Aspergillus fumigatus and yeast Saccharomyces cerevisiae.

Amphotericin B when given along with allicin exhibited enhanced antifungal

activity against S. Cerevisiae.66

Quercetin: Quercetin is shown to increase bioavailability, blood levels and efficacy

of a number of drugs including diltiazem, digoxin and epigallocatechin gallate. It

was found that increased amount of quercetin administered along with

epigallocatechin gallate increased absorption of epigallocatechin gallate from the

intestine.67,68

Morning glory plant (Ipomoea sp.): Lysergol, a phytomolecule is isolated from

higher plants like Rivea corymbosa, Ipomoea violacea and Ipomoea muricata. It

enhances the killing activities of different antibiotics on bacteria and is a promising

herbal bioenhancer.69

Indian Aloe (Aloe vera): The results of two different Aloe vera preparations i.e.

whole leaf extract and inner filled gel indicate that the aloes improve the absorption

of both the vitamin C and E. The absorption is slower and vitamins last longer in the

plasma with aloes. This increases bioavailability of Vitamin C and E in human. Aloe

vera is a very promising future nutritional herbal bioenhancer.70

Genistein: Genistein is reported to be able to inhibit P-gp, BCRP and MRP-22

efflux function. When co-administered with genistein the intestinal absorption of

paclitaxel, a substrate for efflux transports such as P-gp and MRP2 was dramatically

increased.71

Sinomenium acutum: Paeoniflorin is used in the treatment of inflammation and

arthritic conditions but has a poor absorption rate and thus a very low bioavailability

(3 – 4%) when administered orally. Co-administered with sinomenine, an alkaloid

extracted from Sinomenium acutum Thunb. dramatically altered the pharmacokinetic

behaviours of paeoniflorin in rats. The mechanism underlying the increase in

bioavailability of paeoniflorin is explained as sinomenine could decrease the efflux

transport of paeoniflorin by P-gp in the small intestine.72

Cow urine distillate (Kamdhenu ark): Cow urine distillate is more effective as a

bioenhancer than cow urine. It enhances the transport of antibiotics like rifampicin,

tetracycline and ampicillin across the gut wall by 2-7 folds. It also enhances the

potency of taxol against MCF-7 cell lines. It enhances the bioavailability of

rifampicin by 80 fold in 0.05μg/ml concentrations, ampicillin by 11.6 fold in

0.05 μg/ml concentrations and clotrimazole by 5 fold in 0.88 μg/ml concentrations.

Cow urine also has antitoxic activity against the cadmium chloride toxicity and it

can be used as a bioenhancer of zinc. The bioenhancing ability is by facilitating

absorption of drugs across the cell membrane.73,74

In recent years, polymers those are derived from plant origin have evoked

tremendous interest because of their diverse pharmaceutical applications such as

diluent, binder, disintegrant in tablets, thickeners in oral liquids, protective colloids

in suspensions, gelling agents in gels, and bases in suppository. They are also used

in cosmetics, paints, textiles, and paper making.75 These mucilages are preferred

over the synthetic ones because they are biocompatible, cheap and easily available

than the synthetic ones. Also the natural excipients are preferred on the synthetic and

semi-synthetic ones because of their lack of toxicity, low cost, soothing action,

availability and non-irritant nature of the excipients. Demand for these substances is

increasing and new sources are being developed. India, because of its geographical

and environmental position, has traditionally been a good source for such products

among the Asian countries.76

Mucilages are generally normal products of metabolism (physiological

products), formed within the cell (intracellular formation). They form slimy masses.

Mucilage is a dense, sticky substance that is made by almost all plants and also by a

number of microorganisms. Basically, mucilage is a polar glycoprotein as well as an

exopolysaccharide. In plants, mucilage has an important role in storing water as well

as food, germination of seeds and also the congealing the membranes.77

1.10. ADVANTAGES OF NATURAL MUCILAGES IN PHARMACEUTICAL

SCIENCES

The following are a number of the advantages78 of natural plant–based

materials.

a) Biodegradable: Naturally available biodegradable polymers are produced by all

living organisms. They represent truly renewable source and they have no adverse

impact on humans or environmental health (e.g. skin and eye irritation).

b) Biocompatible and non-toxic: Chemically, nearly all of these plant materials are

carbohydrates composed of repeating sugar (monosaccharides) units. Hence, they

are nontoxic and biocompatible.

c) Low cost: It is always cheaper to use natural sources. The production cost is also

much lower compared with that for synthetic material.

d) Environmental-friendly processing: Mucilages from different sources are easily

collected in different seasons in large quantities due to the simple production

processes involved.

e) Local availability: In developing countries, governments promote the production

of plant rich in mucilage because of the wide applications in a variety of industries.

f) Better patient tolerance as well as public acceptance: There is less chance of

side effects and adverse effects with natural materials compared with synthetic one.

For example: PMMA, povidone

g) Edible sources: Most mucilages are obtained from edible sources.

1.11. DISADVANTAGES OF NATURAL MUCILAGES79,80

a) Microbial contamination: The equilibrium moisture content present in the

mucilage is normally 10% or more and structurally they are carbohydrates and

during production they are exposed to the external environment so there is a chance

of microbial contamination. However, this can be prevented by proper handling and

the use of preservatives.

b) Batch to batch variation: Synthetic manufacturing is a controlled procedure

with fixed quantities of ingredients, while the production of mucilages dependent on

environmental and seasonal factors.

c) Uncontrolled rate of hydration: Due to differences in the collection of natural

materials at different times, as well as differences in region, species, and climate

conditions the percentage of chemical constituents present in a given material may

vary. There is a need to develop suitable monographs on available mucilages.

d) Reduced viscosity on storage: Normally, when mucilages come into contact

with water there is an increase in the viscosity of the formulations. Due to the

complex nature of mucilages (monosaccharides to polysaccharides and their

derivatives), it has been found that after storage there is reduction in viscosity.

1.12. CHARACTERIZATION OF MUCILAGE81

Purity: To determine the purity of the selected mucilage, tests for alkaloids,

glycosides, steroids, carbohydrates, flavonoids, terpenes, amino acids, saponins, oils

and fats, and tannins and phenols are carried out.

Physicochemical Properties: Colour, odour, taste, shape, texture, touch, solubility,

pH, swelling index, loss on drying, hygroscopic nature, angle of repose, bulk and

true densities, porosity and surface tension are estimated. The microbial load and

presence of specific pathogens are also determined. Mucilages are highly viscous in

nature. Therefore, the rheological properties are important criteria for deciding their

commercial use.

Toxicity: The acute toxicity of mucilages are determined by fixed-dose method as

per OECD guideline no. 425.

1.13. EXAMPLES OF SOME MUCILAGES

Abelmoschus Gum: The okra gum is obtained from the fresh fruits of the

plant Abelmoschus esculentus (family Malvaceae). The okra polysaccharide contains

the major polysaccharide component differing widely in the molar ratios of

galactose, galacturonic acid, rhamnose and with some fractions of glucose, mannose,

arabinose, and xylose.82 Mucilage from the pods of Abelmoschus esculentus is

evaluated for its safety and suitability as suspending agent. Mucilage extracted was

found to be nontoxic and was used for formulation of paracetamol suspension.83 The

mucilage was found to be superior suspending agent than tragacanth and its

suspending efficiency was similar to sodium CMC. Mucilage was also evaluated for

its disintegrating property.84 Various concentrations of the mucilage were used and

batches of tablets were formulated and evaluated for dissolution, wetting time, and

disintegration time. The study revealed that Abelmoschus esculentus mucilage

powder was effective as disintegrant in low concentrations (4%).

Mucilage of Abelmoschus esculentus is used as a polymer for the

development of a gastric floating dosage form. In this study, tablet batches were

prepared using Abelmoschus esculentus mucilage and HPMC E15 in different

combinations.84 It was seen that formulation containing Abelmoschus

esculentus mucilage had poor floating capacity but showed sustained release,

whereas formulation containing HPMC had better floating capacity but showed poor

sustained release of the drug, so in all it was seen that formulation containing okra

mucilage with HPMC gave better floating property as well as better sustained

release of the drug. Okra polysaccharide is used as a microbially triggered material

for colon targeted tablet formulation and also as a carrier.85 The observations drive

to conclude that the okra polysaccharide under investigation has the potential to

carry the drug almost intact to the intended site, that is, colon where it undergoes

degradation due to the presence of anaerobic microbes.86

Isapghula Mucilage: Psyllium seed husks, also known as ispaghula, isabgol, or

simply as psyllium, are portions of the seeds of the plant Plantago ovata, a native of

India and Pakistan. Gel forming fraction of the alkali extractable polysaccharides is

composed of arabinose, xylose and traces of other sugars. They are soluble in water,

expand and become mucilaginous when wet. Seeds are used commercially for the

production of mucilage. It is a white fibrous material, hydrophilic in nature and

forms a clear colorless mucilaginous gel by absorbing water. Psyllium seed husk has

been successfully evaluated as binder, disintegrant, release retardant and also pH

sensitive novel hydrogels using N, N methylenebisacrylamide as cross linker and

ammonium per sulfate (APS) as initiator for model drugs (tetracycline

hydrochloride, insulin and tyrosine), for colon specific drug delivery systems.87

Fenugreek Mucilage: Mucilage is obtained from seeds of Trigonella foenum-

graceum (family: Leguminosae). Its seeds contain a high percentage of mucilage

and do not dissolve in water but form viscous tacky mass and swell up when

exposed to fluids. Gum contains mannose, galactose, and xylose. The mucilage

obtained from fenugreek was found to be better release retardant compared to

hypromellose at equivalent content.88,89

Hibiscus Mucilage: Mucilage is obtained from fresh leaves of Hibiscus rosa-

sinensis (family: Malvaceae). Mucilage of Hibiscus rosa-sinensis contains L-

rhamnose, D-galactose, D-galacturonic acid and D-glucuronic acid. The use of its

mucilage for the development of sustained release tablet has been reported.90

Neem Gum: Neem gum is obtained from the fruits of Azadirachta

indica (family: Meliaceae). Gum contains mannose, glucosamine, arabinose,

galactose, fucose, xylose, and glucose. Studies were performed on neem gum for its

binding property and sustained release property. Results show that as the proportion

of Azadirachta indica fruit mucilage increases, the overall time of release of the

drug from the matrix tablet also increases.91

Aloe Mucilage: Aloe mucilage is obtained from the leaves of Aloe

barbadensis (family: Liliaceae). It contains arabinan, arabinorhamnogalactan,

galactan, galactogalacturan, glucogalactomannan, galactoglucoarabinomannan and

glucuronic acid containing polysaccharides. A controlled delivery system of

glibenclamide using aloe mucilage was studied. Various formulations of

glibenclamide with Aloe barbadensis Miller leaves mucilage were prepared by

direct compression technique. The formulated matrix tablets were found to have

better uniformity of weight and drug content with low statistical deviation. The

swelling behaviour and in-vitro release rate characteristics were studied. The

dissolution study proved that the dried Aloe barbadensis Miller leaves mucilage can

be used as a matrix forming material for making controlled release glibenclamide

matrix tablets.92

Phoenix Mucilage Phoenix mucilage is obtained from the dried fruit of Phoenix

dactylifera (family: Palmaceae). Carbohydrates make up to 44–88% of the fruit,

which include mainly reducing sugars such as fructose, sucrose, mannose, glucose

and maltose in addition to small amounts of polysaccharides such as pectin (0.5–

3.9%), starch and cellulose. Binding properties of date palm mucilage were

successfully evaluated. The tablets manufactured using phoenix mucilage were

found to be less friable than tablets manufactured using acacia and tragacanth. As

the concentration of the gum increased the binding ability improved, producing good

uniformity in weight and hardness of the tablets.93

Cassia tora Mucilage: Cassia tora mucilage derived from the seeds of Cassia

tora (family: Caesalpiniaceae). The primary chemical constituents of Cassia include

cinnamaldehyde, gum, tannins, mannitol, coumarins and essential oils (aldehydes,

eugenol, and pinene); it also contains sugars, resins, and mucilage among other

constituents. Studies were performed on Cassia tora mucilage for its binding

property.94 It was observed that increasing the concentration of mucilage increases

hardness and decreases the disintegration time of the tablets which were formulated

with different concentrations of Cassia tora gum. This mucilage was also evaluated

for its suspending agent. The suspending ability of Cassia tora mucilage was

compared with that of tragacanth, acacia and gelatin. The suspending ability of all

the materials was found to be in the order: Cassia tora > tragacanth gum > acacia

gum. Gelatin results suggest that suspending action of the mucilage is due to high

viscosity of the gum.95

Mimosa Mucilage: Gum is obtained from seed of Mimosa pudica

(family: Mimosaceae) . Seed mucilage is composed of D-xylose and D-glucuronic

acid. Mimosa seed mucilage hydrates and swells rapidly on coming in contact with

water. A controlled delivery system for diclofenac sodium using Mimosa seed

mucilage was studied. In this study different batches of tablets were formulated and

their drug release were checked. It was observed that as the proportion of

the Mimosa pudica seed mucilage increases, there is a decrease in release of drug,

the mechanism of release being diffusion for tablets containing higher proportion of

mucilage, and a combination of matrix erosion and diffusion for tablets containing

smaller proportion of mucilage. Studies showed that as the proportion of the

mucilage increased, there was a corresponding increase in percent swelling and

decrease in percent erosion of the tablets.96

Dendrophthoe Mucilage: Dendrophthoe mucilage is obtained from dried as well as

fresh stem parasite of Dendrophthoe falcate (family: Loranthaceae) on Magnifera

indica (family: Anacardiaceae). Mucilage of Dendrophthoe falcata was evaluated as

a binder for pharmaceutical dosage forms Wet granulation was employed to make

tablets with Dendrophthoe falcate mucilage.97 Different concentrations of mucilage

were used in formulation. It was observed that 6% w/w binder concentration showed

more optimum results as tablet binder.

Cocculus Mucilage: Mucilage is obtained from leaves of Cocculus hirsute

(family: Menispermaceae). Mucilage contains polysaccharides and a gelatinous type

of material. Leaves are used topically as emollient and demulcent. It has been

nontoxic to human skin. Gelling property of this mucilage was studied. This was a

comparative study. Flurbiprofen was used as a model drug for the formulation of

gel. Marketed flurbiprofen gel and gel prepared from Cocculus hirsute leaf powder

were compared and both the gels were evaluated for anti-inflammatory property. It

was observed that the quantity of drug released from prepared test gel and its anti-

inflammatory activity was found to be more than that of marketed gel.98

Cordia Mucilage: Cordia mucilage is obtained from raw fruits of Cordia obliqua

(family: Boraginaceae). Cordia mucilage can be used as expectorant, is effective in

treating lung disease and raw gum can be used in gonorrhoea. Studies were

performed99 on Cordia mucilage for binding and emulsifying properties.

Ocimum Mucilage: Ocimum mucilage is obtained from the seeds of Ocimum

americanum commonly called Ocimum canum (family: Lamiaceae). Mucilage

contains xylose, arabinose, rhamnose, and galacturonic acids. The mucilage was

found to have disintegrating property. The disintegration time for tablet formulations

prepared using ocimum mucilage was less than tablets that were prepared by using

starch as a disintegrant.100

The use of natural mucilage for pharmaceutical applications is attractive

because they are economical, readily available, nontoxic, capable of chemical

modifications, potentially biodegradable, and with few exceptions, also

biocompatible. Majority of investigations on natural polymers in drug delivery

systems centre around polysaccharides. Mucilages can also be modified to have

tailor-made products for drug delivery systems and thus can compete with the

synthetic excipients available in the market. Though the use of traditional mucilages

has continued, newer mucilages have been used, some of them with exceptional

qualities. There is huge scope for research on newer mucilages obtained from plants

and could be further exploited in future as a novel natural polymer for development

of different drug delivery systems in pharma industry.101

1.14. CAPSULES - AN OVERVIEW

Capsules are gelatin shells filled with the ingredients that make up an

individual dose. Dry powders, semi-solids and liquids that do not dissolve gelatin

may be encapsulated. Capsules account for about 20% of all prescriptions

dispensed.102-105

Capsules have several advantages as pharmaceutical dosage forms:

1. The unpleasant tastes, aromas or appearance of a drug can be masked

2. Powders can be dispensed in an uncompressed form, thus allowing for

quicker dissolution and absorption of the drug following oral dosing (as

compared with tablets)

3. Offer the pharmacist versatility to prepare any dose desired for a variety of

administration routes (e.g. oral, inhalation, rectal or to be diluted for vaginal,

rectal, oral or topical use)

4. The release rate of the drug can be altered

Their disadvantages or limitations include the following:

Easily tampered (although techniques exist for preventing this)

They are subject to the effects of relative humidity and to microbial

contamination

They may be difficult for some people to swallow

More expensive (commercially)

1.14.1. HARD GELATIN CAPSULES

The hard gelatin capsule consists of a base or body and a shorter cap, which fits

firmly over the base of the capsule. For human use, eight sizes of capsules are

available. The capacity of each size varies according to the combination of drugs

and their apparent densities. Capsules are available as clear gelatin capsules or in a

variety of colors. Some types of hard gelatin capsules have a locking cap, which

makes it more difficult to reopen the capsule.

The relative sizes and fill capacities of capsules are given below (Table 2). By

knowing the bulk density of fill material, proper choice of capsule size is usually

made easier.

Table – 2: Capsule size and their capacity

Capsules are made of gelatin, sugar and water. It contains about 10% to 15%

moisture. Gelatin can absorb upto ten times its weight in water. So if gelatin

capsules are placed in areas of high humidity, they become malformed as they

absorb moisture. On the other hand, if capsules are placed in low humidity, they

become dry and brittle and may crack. To protect capsules from the extremes of

humidity, they should be dispensed in plastic or glass vials and stored in a cool, dry

place. It appears that a storage relative humidity of 30% to 45% is best. Cotton can

be placed in the top of the vial to keep the capsules from rattling.

Capsules should be visually inspected and checked for

Uniformity - check capsules for uniformity in appearance and color

Capsule Size Volume (ml)

000 1.37

00 0.95

0 0.68

1 0.50

2 0.37

3 0.30

4 0.20

5 0.13

Extent of fill - check capsules for uniformity of extent of fill to ensure that

all capsules have been filled

Locked length- check capsules to ensure that they have all been tightly

closed and locked

The present work is about the isolation, characterization of the mucilage from

Cardiospermum halicacabum and to incorporate it as a bioenhancer with

leflunomide which is commonly being prescribed to patients with rheumatoid

arthritis and to formulate it as a capsule.