Plant tannins as inhibitors of hydroperoxide production and tumor promotion induced by ultraviolet B radiation in mouse skin in vivo.
The anti-oxidant and anti-tumor promotion activities of several tannins extracted from plants were examined in mouse skin treated with ultraviolet B (UVB) radiation in vivo. Hydroperoxide production was found to be maximally stimulated at a UVB dose of 200 mj/cm2, beyond which no further stimulation occurred. Treatment of mouse skin with two UVB doses of 225 mj/cm2 each, applied at a 48 h interval gradually increases the hydroperoxide (HPx)-producing activity of the epidermis, which is maximally stimulated at 4 days and returns to control levels at 15 days. The magnitude of the HPx response is found to increase with repeated UVB treatments applied at a 48 h interval and reaches a maximum level following four treatments. Of the three tannins tested (Commercial TA, Tarapod TA, and Oak TA), Tarapod TA is found to be the most effective inhibitor of UVB-stimulated HPx activity. Pretreatment with Tarapod TA inhibits, in a dose-dependent manner, this HPx response to UVB radiation. Inhibition by Tarapod TA occurs when it is applied at distant times before (-12 h) or after (+24 h) UVB radiation. When applied 20 min before UVB radiation, twice a week for 25 weeks, 8 mg of Tarapod TA inhibits the incidence and yield of papillomas promoted by UVB light in initiated skin by 34 and 70% respectively. Furthermore, when 10 mg/kg of mouse body weight of Tarapod TA was injected intraperitoneally, for a period of 25 weeks, 20 min prior to UVB treatment, it inhibited the yield of papillomas by 44%, suggesting that plant tannins when administered by various means are useful photoprotectants.
Gali-Muhtasib
H U
HU
Department of Biology, American University of Beirut, Beirut, Lebanon.
Yamout
S Z
SZ
Sidani
M M
MM
D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000627:therapeutic use*; D005260:Female; D006861:Hydrogen Peroxide / Q000378:metabolism*; D051379:Mice; D008812:Mice, Hairless; D009381:Neoplasms, Radiation-Induced / Q000517:prevention & control*; D020011:Protective Agents / Q000627:therapeutic use*; D012867:Skin / Q000473:pathology / Q000528:radiation effects*; D012878:Skin Neoplasms / Q000517:prevention & control*; D013634:Tannins / Q000627:therapeutic use*; D013997:Time Factors; D014466:Ultraviolet Rays
D000972:Antineoplastic Agents, Phytogenic; D020011:Protective Agents; D013634:Tannins; D006861:Hydrogen Peroxide