Hydrolyzable tannins: Potent inhibitors of hydroperoxide production and tumor promotion in mouse skin treated with 12‐O‐tetradecanoylphorbol‐13‐acetate in vivo

Abstract

The anti-oxidant and the anti-tumor-promotion activities of several hydrolyzable tannins (HTs), including a commercial tannic-acid (TA) mixture, were examined in mouse skin treated with 12-O-tetradecanoylphorbol-13-acetate (TPA) in vivo. A single application of TPA gradually increases the hydroperoxide (HPx)-producing activity of the epidermis, which is maximally stimulated at 3 days and returns to control levels at 9 days. Pre-treatments with TA and ellagic acid (EA) strongly inhibit, in a dose-dependent manner, this HPx response to TPA. Total inhibition by TA lasts for about 16 hr, beyond which it is substantially reduced but not completely lost. TA can also reduce the level of epidermal HPx when it is applied 36 hr after the tumor promoter. EA is an antioxidant 10 times more potent than TA and n-propyl gallate (PG), which are equally effective against TPA-induced HPx production. Gallic acid is the least effective of the HTs in inhibiting HPx formation. TA also inhibits the production of HPx induced by several structurally different tumor promoters and the greater HPx responses produced by repeated TPA treatments. When applied 20 min before each promotion treatment, twice a week for 45 weeks, several HTs inhibit the incidence and yield of papillomas and carcinomas promoted by TPA in initiated skin. Overall, TA is more effective than EA and PG in inhibiting skin-tumor promotion by TPA, suggesting that the anti-oxidant effects of HTs are essential but not sufficient for their anti-tumor-promotion activity.

Tannic Acid Is a Natural β-Secretase Inhibitor That Prevents Cognitive Impairment and Mitigates Alzheimer-like Pathology in Transgenic Mice

“…For example, TA has been reported to have antioxidant and anti-inflammatory properties (76,77), and we went on to determine whether the compound impacted neuroinflammation, an important AD pathoetiologic hallmark (53,54), in PSAPP mice. Interestingly, oral TA treatment reduced microgliosis, astrocytosis, and expression of the proinflammatory cytokines TNF-␣ and IL-1␤ in PSAPP mice.…”

Resveratrol–Cu(II) induced DNA breakage in human peripheral lymphocytes: Implications for anticancer properties

“…As already mentioned several classes of plant-derived antioxidant polyphenols also exhibit oxidative DNA degradation properties particularly in the presence of transition metal ions such as copper. Evidence in the literature suggests that antioxidant properties of these polyphenols may not fully account for their anticancer effects [27]. Further, we have previously shown that the polyphenol gallic acid is highly efficient in DNA degradation as compared with syringic acid (where two of the hydroxyl groups of gallic acid are modified) [28].…”

Eco-Friendly Soaking Process Using Tannic Acid as an Alternative Bactericide

“…The use of vegetable tannins such as quebracho, mimosa, gall-nut, chestnut and valonia as a biocide in leather soaking process was also studied [18] owing to their antimicrobial and antiseptic properties [19]. Tannic acid, which is a commercially important hydrolysable gallotannin, has also got a great deal of attention as an antimicrobial agent due to its antimicrobial, antimutagenic, anticarcinogenic and antioxidant properties [1, 3,4,10,22,23,31,35,37,41,44]. Tannic acid is present in a variety of fruits and vegetables including tea, cocoa, beans, grapes, strawberry, persimmon, especially the bark of the oak species, sumac and myrobalan [1, 11,40] and also categorized as a 'generally recognized as safe' (GRAS) food additive [1].…”