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Original Article

Antioxidant perspective of selected medicinal herbs in India:A probable source for natural antioxidants

Shanmugaraj Bala Murugan, Ramamoorthy Deepika, Aziz Reshma,Ramalingam Sathishkumar*

Plant Genetic Engineering Laboratory, Department of Biotechnology, Bharathiar University, Coimbatore, Tamil Nadu, India

a r t i c l e i n f o

Article history:

Received 28 March 2013

Accepted 22 April 2013

Available online 16 May 2013

Keywords:

Antioxidant activity

Flavonoids

Free radicals

Medicinal plants

Phenolics

* Corresponding author. Tel.: þ91 9360151669E-mail address: rsathish@buc.edu.in (R. S

0974-6943/$ e see front matter Copyright ªhttp://dx.doi.org/10.1016/j.jopr.2013.04.023

a b s t r a c t

Objective: To analyze the phytochemical and radical scavenging activities of leaf fractions of

commonly used 6 medicinal plants in India.

Methods: The plant leaves were extracted with 80% methanol. The methanolic extracts

were subjected to total flavonoids and phenolics estimation. Antioxidant activities of the

extracts were determined by DPPH (2,2-diphenyl-1-picrylhydrazyl) and FRAP (Ferric ion

reducing antioxidant power) assay.

Results: Our results showed that Phyllanthus amarus had higher levels of flavonoids

(57.18 mg/100 g) and phenolics (46.92 mg/g). All the extracts showed significant antioxidant

activity. The highest DPPH radical scavenging activity was found in Leucas aspera (75.06%)

followed by Coleus aromaticus (72.26%). The highest FRAP value was observed in the P.

amarus (12.68 mM/g) whereas L. aspera (2.11 mM/g) showed the lowest. The results suggest

that the secondary metabolites like polyphenolics and other compounds present in these

plants may contribute to the medicinal properties of that plant.

Conclusions: The results concluded that P. amarus have relatively more phytochemical

content and showed significant antioxidant activity. Our finding is a prologue for charac-

terization and isolation of antioxidant components from the medicinal plants and invitro

and invivo studies are essential to use it as a potential source of natural antioxidants.

Copyright ª 2013, JPR Solutions; Published by Reed Elsevier India Pvt. Ltd. All rights

reserved.

1. Introduction Leucas aspera etc.2 In olden days, different medicinal plant

In ancient times, humanswere healthy, havingmore immune

power; themain reason for their better healthwasmay be due

to their life style and food habits. In prehistoric times, people

took food asmedicine. Tribals depend on themedicinal plants

on their day-to-day life starting from food to health care.1 The

ethno botanical reports provide the information on impor-

tance of several medicinal plants like Phyllanthus amarus,

; fax: þ91 422 2422387.athishkumar).2013, JPR Solutions; Publi

species have been used for the treatment of human ailments

ranging from fever to cancer. But now the concept is shifted to

‘Medicine as food’ due to the fast food culture by the modern

societies.3 In the modern era, the changing life style of the

present generation forms the basis for the occurrence ofmany

new diseases that is challenging the day-to-day life of the

humans. Even with the discovery of many novel drugs that

can cure the disorders, the affordability, especially for those in

shed by Reed Elsevier India Pvt. Ltd. All rights reserved.

j o u rn a l o f p h a rma c y r e s e a r c h 7 ( 2 0 1 3 ) 2 7 1e2 7 4272

developing countries is the major limitation. For the past two

decades, humans were in search of effective drugs that will

combat deadly diseases without any side effects.

Free radicals are responsible for the etiology of high

number of chronic and degenerative diseases. Free radicals

are highly active, unstable compounds due to the presence of

unpaired electron in their outer shell, which are produced as

result of cellular metabolism. Lipid peroxidation depicts the

cellular injury and oxidative stress damage.4 Antioxidants

present in the human body protect during oxidative stress.

There is a long history of medicinal usage of plants for the

treatment of human disorders. Plants possess many second-

ary metabolites, which render beneficial properties to

humans.5 Phytochemicals are the secondary metabolites

produced by plants that are responsible for the smell, color

and flavor of fruits/vegetables/plant foods. Phytochemicals

present in the plants are reported to have antioxidants prop-

erties that will prevent the oxidative chain reaction initiated

by the free radicals and counteract the damaging effects of

reactive oxygen species (ROS) produced within the organism

from molecular oxygen.6 Earlier food was viewed only as a

primary source of nutrition to meet our daily minimum re-

quirements for basic survival, but now interest is shiftedmore

toward identifying/improving the functionality of food.

Hence, the aim of the present study is to scientifically evaluate

the antioxidant properties of 6 commonly used medicinal

plants in India.

2. Materials and methods

2.1. Sample collection

The medicinal plants used in the present study (Andrographis

paniculata, Cissus quadrangularis, C. aromaticus, L. aspera, Oci-

mum americanum, P. amarus) were authenticated by Prof. S.

Ramachandran, Taxonomist, Department of Botany, Bhar-

athiar University, Tamil Nadu, India.

2.2. Preparation of extracts

The leaves from the plants were collected and cleaned with

distilled water. The leaf samples (1 g) were weighed and ho-

mogenized in 10 ml of methanol in a mortar and pestle. The

samples were then centrifuged at 4000 rpm for 10 min. The

above procedure was repeated twice and the extracts were

collected and stored for the further analysis.

Fig. 1 e Total flavonoid content in 6 different medicinal

plant extracts.

2.3. Phytochemical content and radical scavenginganalysis

The total flavonoid content in the extract was estimated by

aluminum chloride method.7 The total phenolic content was

quantified by FolineCiocalteu method and the values were

expressed in gallic acid equivalents (GAE).8 The DPPH radical

quenching ability of the leaf vegetable extracts was measured

at 517 nm.9 The ability of the plant extracts to reduce the

ferrous ions was measured using the method of Benzie and

Strain.10

2.4. Statistical analysis

All the experiments were repeated 3 times and the results

represented are the means of 3 replicates � SD.

3. Results and discussion

3.1. Phytochemical content

The total flavonoid content of all the medicinal plants was

evaluated and the results expressed in quercetin equivalents

(Fig. 1). The results showed considerable total flavonoids

content in all the plants tested. Total flavonoid content of the

selected 6 medicinal plants showed significant variation,

ranging from 49.72 to 57.18 mg Quercetin (QE)/100 g fresh

weight with an overall mean of 53.63 mg QE/100 g. P. amarus

showed the highest flavonoid content (57.18 mg QE/100 g)

while it was lowest in C. aromaticus (49.72 mg QE/100 g). The

total phenolic content in the methanolic extracts of all the 6

medicinal plants were systematically assessed and the results

were expressed in gallic acid equivalents (Fig. 2). Total

phenolic content showedmarked difference among the plants

studied; P. amarus (46.92 mg GAE/g) had maximum phenolic

content and Cissus quandrangularis (8.18 mg GAE/g) had least

phenolic content. P. amarus was followed by C. aromaticus

(42.82 mg GAE/g), L. aspera (29.41 mg GAE/g) and A. paniculata

(17.11 mg GAE/g).

The results revealed that P. amarus showed significant

flavonoid and phenolic content, which is correlated with the

earlier reports.11 In this study, the phenolic compounds were

assessed by FolineCiocalteau reagent that does not give the

complete picture of phenolics, however this assay will help to

categorize the extracts based on their antioxidant potential.8

The phenolic content of the medicinal plants vary consider-

ably which may be due to the high solar radiation and

temperature.12

3.2. Determination of radical scavenging activity

The primary characterization of scavenging ability of the

plant extracts has been studied using a stable free radical

DPPH. The results of radical scavenging activity of all the

medicinal plants are shown in Fig. 3. Among the plants

Fig. 2 e Total phenolic content in 6 different medicinal

plant extracts.

Fig. 4 e FRAP reducing power in 6 different medicinal plant

extracts.

j o u r n a l o f p h a rm a c y r e s e a r c h 7 ( 2 0 1 3 ) 2 7 1e2 7 4 273

analyzed, the highest DPPH radical scavenging activity was

found in the leaves of L. aspera (75.06%), whereas it was lower

in C. quandrangularis (42.86%). Many published data showed

that phenolic compounds are responsible for the antioxidant

activity of the plants.13,14 In contrast, despite the high flavo-

noid and phenolic content in Phyllanthus, its DPPH radical

scavenging activity was really low, suggesting that the anti-

oxidant activity of the plant extract may not be due to the

specific group of secondary metabolites like polyphenolics,

which may be due to the combined groups of metabolites.15,16

The antioxidant power of the medicinal plant extracts

were assessed by FRAP assay. The FRAP values of all the me-

dicinal plant extracts were given in Fig. 4. Ferric Ion Fe (II)

reducing ability hadmarked differences among the plants and

it was maximum in P. amarus (12.68 mM/g) and lowest in L.

aspera (2.11 mM/g). With regard to FRAP values, Phyllanthus

showed remarkable reducing power as compared to the other

medicinal plants tested. By using FRAP assay, several groups

reported the reducing power of other medicinal plants like

Ocimum, A. paniculata and Cissus quadrangularis.17e19

3.3. Relationship between phytochemical content andradical scavenging activity

The correlation coefficients between the radical scavenging

activity and total flavonoids/phenolics were calculated. The

DPPH radical scavenging activity did not correlate with

flavonoid (r ¼ 0.518, p > 0.05) and phenolic content (r ¼ 0.412,

Fig. 3 e DPPH radical scavenging activity in 6 different

medicinal plant extracts.

p > 0.05). Also there is no significant linear correlation was

found between the FRAP values with flavonoid (r ¼ 0.449,

p > 0.05) and phenolic content of the medicinal plants tested

(r ¼ 0.429 p > 0.05). Although there are some reports20,21

showing a high correlation between the radical scavenging

activity and phytochemical content, other authors15 have

found a low correlation. In the present study, no linear cor-

relation was observed between the phytochemical content

and antioxidant activity. The variation in the antioxidant ac-

tivity of the extracts may be due to the difference in the

methodology adapted.16

4. Conclusion

In the present study, total flavonoid, total phenolic contents

and radical scavenging activities of 6 selected medicinal

plants were assessed. In this study, out of 6 medicinal plants

tested, P. amarus had the maximum phytochemical and anti-

oxidant activity followed by L. aspera. Still extensive studies

are needed to evaluate the phytochemical and pharmacolog-

ical activities of specific lead compounds in order to use these

plants as a probable source for the potential natural

antioxidants.

Conflicts of interest

All authors have none to declare.

Acknowledgments

The authors are very thankful to The Department of

Biotechnology, Bharathiar University, Coimbatore, Tamil

Nadu, India for supporting this research through DST-FIST

and UGC-SAP funds

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