Antibacterial Spectrum of Plant Polyphenols and Extracts Depending upon Hydroxyphenyl Structure

Abstract

Recently, many biochemical and epidemiological studies have revealed that polyphenols of various foods and herbs have benefits to human health, and some extracts of polyphenol-rich plants, such as green tea and grape seed, have been added to foods or supplements. The antibacterial activity of various plant polyphenols and plant extracts have also been evaluated in several pharmaceutical studies. 1,2) Although tea polyphenols and their extracts have been examined in detail, [3][4][5][6] other extracts of polyphenol-rich plants have not been properly evaluated, because the activity of their chemical constituents has not been clearly demonstrated. 7,8) Many reports on the antibacterial activity of pure polyphenols have been published, 4,[9][10][11][12] however, each result was not able to be compared directly because different methods of evaluation were applied and various bacterial species were used. In order to overcome this problem, we compared the activity of a wide variety of polyphenols against many bacterial species to clarify their antibacterial spectrum, using the same standard method of the minimum inhibitory concentration (MIC). As a result, we found a relatively simple structure-activity relationship, and it was applied to the plant extracts containing various types of polyphenols. MATERIALS AND METHODSChemicals Twenty-two pure or partially pure polyphenols and 26 plant extracts were used in this study (Fig. 1). Polyphenols 1-10 were the same as in our previous study. 12)Epigallocatechin (EGC, 1) and epigallocatechin-3-O-gallate (EGCg, 2) were isolated from commercial green tea; punicalagin (3) was isolated from the peel of Punica granatum; tannic acid (4) was purchased from Kanto Chemical Co., Japan; castalagin (5) was isolated from the wood of Castanea crenata; and prodelphinidins (6) were isolated from the bark of Elaeocarpus sylvestris var. ellipticus; geraniin (7) was isolated from the leaves of E. sylvestris var. ellipticus; loquat procyanidins (8) were isolated from the seeds of Eriobotrya japonica; theaflavins (9) was obtained from black tea; and loquat-treated green tea polyphenols (10) were prepared by treatment of commercial green tea with unripe loquat fruit. Gallic acid monohydrate (11) was purchased from Wako Pure Chemical Industries, Japan. Thearubigin (12) was prepared from black tea as follows: aqueous acetone extract was successively partitioned with AcOEt and n-BuOH. The nBuOH layer was concentrated and subjected to Sephadex LH-20 column chromatography. Elution of 50% acetone yielded 12. (ϩ)-Catechin (13) and (Ϫ)-epicatechin gallate (ECg, 14) were isolated from gambir and green tea, respectively. Myricitrin (15) and rutin (16) were obtained from bark of Myrica rubra and flower bud of Sophora japonica, respectively. Theaflavin mixture (17) was separated from AcOEt soluble fractions of aqueous acetone extracts of black tea. Pyrocatechol (18), pyrogallol (19), protocatechuic acid (20), and caffeic acid (21) were purchased from Sigma Aldrich Japan. Resveratrol (22) was isolated from dried...

In-vitro antimicrobial and synergistic properties of water soluble green and black tea extracts

“…This impairment in drug diffusion is a major limitation in the evaluation of the antimicrobial effects of plant extracts using agar diffusion method (Esiome et al, 2006). The conclusion by Taguri et al (2006) that the antimicrobial potency of tea polyphenols is dependent upon bacterial species is consistent with the findings of this study, which showed that, the green and black tea extracts were more active against the Grampositive, S. aureus ATCC 25923 as compared to E. coli ATCC 25923 which is Gram-negative.…”

<i>In vitro</i> evaluation of the antibacterial activity of some medicinal plant extracts against <i>Xanthomonas campestris pv. musacearum</i>

“…They also bind to adhesins, complex with cell wall and inactivate proteolytic macerating enzymes used by plant pathogens (Mohanta et al, 2007;Gurjar et al, 2012). From this it can be presumed that phenolic compounds act at two different points (cell membrane and cell wall), affecting the growth and metabolism of bacteria (Taguri et al, 2006;Stefanovic et al, 2012). Similar results have also been reported in other studies (Rajeshwar et al, 2005;Kuete et al, 2007).…”

“…Therefore, the antibacterial activity of the two species may be explained by the total phenolics content. Many research reports reveal that phenolic compounds contribute to the antimicrobial properties of plant extracts whereby the extent of inhibition depends on the concentration of these compounds (Taguri et al, 2006;Rhouma et al, 2009;Rodriguez et al, 2009;Tian et al, 2009;Zongo et al, 2011;Moteriya et al, 2014).…”

The structure, occurrence and biological activity of ellagitannins: a general review

“…Antibacterial activity is the main type of their interactions [Funatogawa et al 2004, Taguri et al 2006. The effect of the presence of ellagitannins in bacteria has been examined and it has been found that the hydrolysable tannins have an antibacterial effect for a short time (up to seven days), regardless of their molecular weight , Kołodziej et al 2000.…”