Tannin activity gallic acid

The remaining shlklmates in Table III also are relatively simple, well known compounds. The phenolic structures of vanillin (125) and gallic acid (127) and the prephenolic structures of the common quinic acid (128) and chlorogenic acid (129) make them candidates for physiological activity. Gallic acid is the monomer for tannins, biological polymers found in the cotton plant (15, 37). 

With respect to the activity of tannins, Momose et al. [157] have demonstrated that gallic acid exhibits higher activity than the tannins derived from it. Gallic acid was found to induce apoptosis in different cell lines this induced cell death was mediated by ROS such as hydrogen peroxide and superoxide anion, as well as by Ca2+. However, the induction of apoptosis depends on the acid s distinctive structural features rather than on its antioxidative activity [158]. In fact, the... 

The in vivo assay for evaluation of antitumor activity of other tannins and related polyphenols was thus routinely performed by administration of tannins with a single intraperitoneal injection (10 mg/kg) to female ddY mice 4 days before inoculation of sarcoma 180 cells (1 x 10 ). Sixty days after inoculation of the tumor cells, survivors were killed and autopsied. The antitumor activity of each tannin was estimated by the number of regressors and the % increases in the life span (% ILS) [107]. Among approximately 100 polyphenols of different types tested, most of the oligomeric hydrolyzable tannins exhibited a potent activity in contrast to the negligible activity of the monomeric hydrolyzable tannins, proanthocyanidins and their related low-molecular weight polyphenols such as gallic acid, catechins and caffeoyl derivatives. 

Black walnut cultivars Rawlins and Thomas had considerably lower gallic acid levels of -1% dw, quite close to that of the pistachio cultivar Kerman (0.5% dw), and in vitro aflatoxin production for the walnut Thomas and pistachio Kerman were also similar at 45 and 40 J,g/plate, respectively [17], The hydrolysable tannin in pistachios has a core of quinic acid, rather than glucose (unpublished results), and its stereochemistry is such that dimerization of gallic acid moieties to hexahy-droxydiphenic esters, and consequent formation of ellagic acid, cannot occur. Any aflatoxin inhibitory activity is, therefore, dependent on either the tannin itself or gallic acid. 

Prooxidant activity of phenolic compounds Phenolic antioxidants can initiate an autoxidation process and act like prooxidants under conditions that favor their autoxidation. Instead of terminating a free-radical chain reaction by reacting with a second radical, the phenoxy radical may also interact with oxygen and produce quinones (P = 0) and superoxide anion (02 ). PO -I-O2—>P = 0- -02 . Small phenolic compounds which are easily oxidized, such as quercetin, gallic acid, possess prooxidant activity while high-molecular weight phenolic compounds, such as condensed and hydrolyzable tannins, have little or no prooxidant activity. 

Further, phenolic phytochemicals can be targeted for antimicrobial applications. Many phenolic containing Ifuit and herbal products have shown to possess antimicrobial activity agdimsi Listeria monocytogenes (Chung etal. 1990 Hao et al. 1998 Puupponen-Pimia etal. 2001 Sa-gun et al. 2006). Recent research with purified compoimds from natural products has shown that phenolic phytochemicals such as cinnamic acid, cinnamaldehydes, coumarins, capsaicin, and tannins have anti-7/. pylori activity (Bae et al. 1999, 1998 Jones et al. 1997) when caffeic and gallic acid have Staphylococcus aureus inhibitory activity (Kwon etal. 2007). 

Active constituents believe to be tannins other constituents present include gallic acid, villosin, and calcium oxalate. 

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