Persimmon tannin composition and function*

Tianying Zhang, Gang Li and Haizhen Mo Chunxiang Zhi Department of Food Science Institute of Animal Health Inspection

Henan Institute of Science and Technology Veterinary Bureau of Shangshui County Xinxiang City,Henan Province, China Zhoukou City, Henan Province, China

Corrosponding author: Haizhen Mo, email: mohz@163.com, ztyztyzty2.ok@163.com

* This work is supported by Henan Science and Technology Office to HZ. Mo.

Abstract – In accordance to the chemical structure of tannins, persimmon tannin were divided into hydrolysable tannin and condensed tannin. Persimmon contains large amount of condensed tannins. Persimmon tannins comprising a large variety of structures, give persimmon many health function and is the key factors that affect product quality in persimmon processing. This article mainly introduced the research situation of persimmon tannin, health function and prospect that the research of persimmon tannin could go on, could promote the development of the persimmon industry.

Index Terms – persimmon, tannin; composition; health function

I. INTRODUCTION

As improving of living standards, people will not only focus on health function of food, but also on the sensory properties of food. Proanthocyanidins (condensed tannins) have attract many attention for their beneficial effects in nutrition and on health[1]. Persimmon Proanthocyanidins (condensed tannins) have been associated with antioxidant activity, anti-inflammatory activity, and atherosclerosis prevention, and so on [2].

Persimmon fruit contains abundant condensed tannins [3], so it was astringent. Astringency increases with the mean degree of polymerization; Furthmore, small differences in flavonoid configurations can produce significant differences in sensory properties. Epicatechin is more astringent than its chiral isomer catechin. Similarly, the bond location and the identity of the monomeric units influenced the astringency of synthesized dimers and trimers [4, 5]. Condensed tannin is a phenolic oligomer resulting from the polymerization of flavan-3-ol units, which consists of two types of subunits, extension and terminal units[6, 7]. As a final product of the flavonoid pathway, Condensed tannin is an important flavour compound and key factor that affect product quality in persimmon process. The biological activities of persimmon tannin are probably its complex chemical structure and contents, such as the monomeric flavan-3-ol units, the types of interflavan bonds and the degree of polymerization (DP)[8].The composition ， molecular structure and health function of persimmon tannin were summarized in the article. This provides the oretical basis for further research of persimmon tannin and certain significance for the deep processing of persimmon wine, persimmon vinegar, and persimmon leaf tea.

II. TANNIN COMPOSITION AND MOLECULAR STRUCTURE

Persimmon accumulates condensed tannin in fruit and leaf, which is responsible for astringency trait. As early as the first time in 1920, it’s the first time that tannins were divided into thehydrolysable tannins and condensed tannins by Freudenberg et al.[9].In 1954, leucoanthocyanidins were confirmed to be identical with condensed tannins by Bate-Smith. Tannin and anthocyanin linked together for the first time is the great guiding significance for studying the molecular structure of tannins.

Tannins have been defined by Bate-Smith as water soluble phenolic compounds having molecular weights between 500 and 3000, and they have ability to precipitate alkaloids, gelatin and other proteins[10, 11]. In 1923, persimmon tannins were carried out a preliminary study by Japanese scholar Komatsu Matsunami, and were speculated that the basic formula of tannin is C19H20O9. The tannins molecule may contain the root bark phenolics and gallic acid monomers[12]. In 1962, Ito and Oshima extracted of soluble persimmon tannins which is the cause of astringency, had two substances delphinidin and glucose with a strong acid treatment, the main component is leucodelphindin, in its C-3 position on the base with a glucose[13]. Later, Ito and Joslyn studies suggest that persimmon tannin is not only leucodelphindin, may also contain other more complex components. Persimmon tannins was generated not only a large number of leucodelphindin, but also gallic acid,gallocatechin and catechin galate with acid thermal degradation. They believed that persimmon tannins was a class of polymers linked several low molecular weight compounds through the C-C bond. The theory Was first proposed that persimmon tannin was condensed tannins main with delphinidin[14]. In 1977, Matsuo and Ito summarized previous studies and further evidenced the doctrine that persimmon tannin is Proanthocyanidins.

Persimmon tannin was deposited with the K2HPO4 and degradated with benzyl mercaptan. The degradation products separated by silica gel TLC , Identified by H-NMR and the results suggested that the proposed condensed tannins structure consists of four monomer compounds, catechin,gallocatechin,catechin-3-O-gallate and gallocatechin -3-O-gallate, with a molar ratio of 1 : 2 : 1 : 2.These units are

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linked by the C-4 C-6 or C-8 to form a polymer [14, 15]（Fig.1）.

In Ito and Oshima’s study, the main component of

persimmon tannin was named diospyrin, which is leucopetunidim -3-glucosides. The study by Yonemori et al.[16] is that catechin was the main phenolic compounds in persimmon. Small molecular weight components dominated in non-astringent and high molecular weight components dominated in astringent. Fei XQ et al. [17] thought that the main ingredients of persimmon tannin have three kinds, namely gallic acid, epigallocatechin and catechin. Diospyrin（Fig.2） in comparison with the catechins（Fig.3） was found by Chen XN et al. [18] that they are almost the same basic unit, but the individual terminal units. In recent years, with the separation of technology development, the use of HPLC,MS,NMR and other cutting-edge technology, more and more condensed tannins were isolated and identified.

Fig.2 Molecular Structure of diospyrin

Fig.3 Molecular Structure of catechin

At present, five different flavan -3- alcohol such as

catechin, epicatechin, epigallocatechin, epigallocatechin-3-O-gallate, epicatechin-3-O-gallate were isolated from the persimmon fruit and leaves.Purification of persimmon tannin with AB-8 macroporous resin, Gu HF et al.[19] divided it into small molecular weight tannins tannins and high molecular weight tannins with 10000Da of polysulfone ultrafiltration membrane and used thiolysis-HPLC to evaluate high molecular weight tannin.The degradation products are epicatechin, epigallocatechin - 3 - O-gallate, epicatechin - 3 - O-gallate and an unknown Monomer, the products of three known to exist in the ratio of 1:73:1. Akagi et al.[20]analyze the condensed tannin fractions, epicatechin - phloroglucinol adducts, epicatechin - 3 – 0 – gallate - phloroglucinol adducts, epigallocatechin - phloroglucinol adduct and an unknown substance by acid catalytic degradation - HPLC method in the case of excess pyrogallol. The unknown component recognized as a form epigallocatechin-3-0 - gallate - phloroglucinol adducts was separated by TLC method and then charactered charactered by mass spectrometry, nuclear magnetic resonance.

Epigallocatechin-3-0-gallate - phloroglucinol adduct is the most important component of persimmon.In phloroglucinol analyses of condensed tannins in persimmon fruit,few hydrolyzed monomers for the terminal CT units were also found. This indicates a high degree of CT polymerization in persimmon fruit, which is consistent with a previous report by Matsuo and Ito [14] .Condensed tannin, was analyzed by HPLC-MS after extracted with 70% aqueous acetone and thiolysis by Kawakami [21]. The main component is procyanidins oligomer consist of one terminal units of

Fig.1 Chemical structures of persimmon tannin and related catechin

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catechin and four heterogeneous extensions unit, including epicatechin - 4 - BTE (benzylthioether), epigallocatechin - 3 -0- gallate - 4βBTE, epicatechin - 3 -0- gallate - 4β- BTE, epigallocatechin - 4β- BTE. Proanthocyanidins (condensed tannin) is a class of flavan-3-ol polymer formed different compounds, because its polymerization degree,componentunit, connecting way, causing the analytic determination more difficulty[22]. In the following two decades, As a consequence tannins, except for lower molecular weight oligomers which can be more easily separated, have been mostly overlooked.

III. FUNCTION OF TANNIN AND ITS APPLICATION

A. Action of antibacterial and antiviral Studies by Akiyama et al. [23] showed several tannins such as tannic acid, gallic acid, ellagic acid, epicatechin epigallo-catechin gallate, and epicatechin can inhibit Staphylococcus aureus. Hara and Kudo et al. [24] reported that Japanese persimmon leaves extracts can quickly have an effect on L. Listeria monocytogenes and Vibrio parahaemolyticus at low content. Japanese medicine in research of tannins to a variety of toxins inhibitory effect, found that persimmon tannins can inhibit the activity of the snake venom protein and have a strong toxin detoxication of Taiwan's cobra, Philippines cobra, India cobra[25]. Gu HF et al. [26] reported that several enzymes activity such as proteolytic enzymes, phospholipase A2, L-amino acid oxidase activity from Agkistrodon halys Pallas, Agkistrodon acutus, and cobra venom could be significantly inhibited by persimmon tannin in vitro. Binding of an important cause of persimmon Tannin and protein led to enzyme inactivation.

B. The antioxidant activity of tannin Plant tannin has antioxidant and free radical scavenging

activity, a large number of studies have shown that lipid peroxidation induced by oxygen free radicals is closely related with many diseases [27]. Gorinstein et al. [28] studies have shown that persimmon peel and pulp has significant antioxidant effect on antiatheroscloresis and lowering cholesteroling on the laboratory mouse, so it can be recommended as the anti-atherosclerosis food. Ahn [29] found that extracts of persimmon nuclear has free radical scavenging capacity in vivo. The study by Han et al. [30] indicated that methanol extracts of persimmon leaves have free radical scavenging ability and can inhibit lipid peroxidation in cells. Gu HF et al. [31] found that high molecular weight tannins is 83.6% percentage of total tannins. Using a variety of system to evaluat the antioxidant capacity of persimmon tannin, the results showed the high molecular weight tannins in different antioxidant systems have shown superior results on the hydroxyl radical, superoxide anion radical scavenging. In Ito and Oshima [32] study, the persimmon tannin has a catechol and a pyrogallol, and catechol and pyrogallol in the ortho-phenolic hydroxyl groups are easily oxidized, thus depleting the environment of oxygen. Katsube et al [33] have found 70% ethanol extract of astringent persimmon has a strong anti-LDL (low density lipoprotein) oxidation. Xu SL [34]

found that alcohol extracts of persimmon has a better total antioxidant activity.

C. Lower cholesterol, prevent cardiovascular and cerebrovascular diseases

Kawakami et al. [21] feeding rats with condensed tannins of Persimmon, can lower cholesterol levels. It is considered condensed tannin restrain pancreatic α-amylase activity. Tannins can reduce cholesterol absorption in intestinal to lower lipid concentrations, and reduce the incidence of cardiovascular disease [31].

D. Quench the fluorescence of Bovine serum albumin (BSA) Gu HF et al.[35]studied persimmon tannin have effect on

quenching the fluorescence of bovine serum albumin (BSA) in the physiological pH by fluorescence spectroscopy and UV absorption spectroscopy, the results showed that the combination of persimmon tannin and BSA by the hydrophobic forces and electrostatic forces electrostatic forces causes occurred regularly of the BSA fluorescence quenching. Quenching mechanism is static quenching.

E Other function Some polymer tannin has obvious anti-allergic effects, and its activity is related with the degree of polymerization [31]. Achiwa [36] suggest that persimmon tannin can inhibit C- nitro and C - nitroso compounds in the mutagenicity effect. Nakayama et al.[37] have shown that condensed tannin of persimmon leaf may prevent high-fat obesity.

As the convergence of persimmon tannin, it is mouth feel astringent after eating, and reacted with dietary protein, carbohydrates to form complexes which affect gastric enzymes and absorption of the iron, calcium in the digestive tract. After into the intestines, the tannin caused secretion of intestinal fluid decreased. We should try to understand the pros and cons of tannin, it will be contribute to more comprehensive understanding and studying it in depth.

IV. FORECAST The cultivation of persimmon has a long history in China and Japan. The production and acreage of China kept the highest in the world. Because most persimmon tree planted in China are astringent persimmon variety, and the fruit contains a lot of persimmon tannin which seriously affect the storage, distribution and processing. It’s a broad problem exist in persimmon fruit products, so further theories study need to do to learn the persimmon metabolic path and chemical structure change during processing. Due to complex structure and properties of persimmon tannins, it easily causes tannin reversion after irritation and turbidity processing. Only more comprehensive understanding of persimmon tannin, can use it widely, and then can solve related problem in persimmon process industry. Thus the research can bring about greater social and economic benefits.

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