GAC FRUIT PREVENTS OXIDATIVE DNA DAMAGE INDUCED BY H₂O₂ AND UVC IN TK6 HUMAN LYMPHOCYTES BY COMET ASSAY

Momordica cochinchinensis or ‘GAC’ of family Cucurbitaceae is indigenous vegetable and fruit to Southeast Asia. In Thailand, it is called ‘Fak Khao’. Its young fruits are consumed as traditional food. Recent studies indicated that the GAC fruit has high carotenoids content, particularly lycopene and beta-carotene. The aim of this study was to determine biological activity of GAC extracts on H₂O₂ and UV-induced DNA damage in TK6 cells. GAC extracts were prepared from three parts of mature fruits including pulp (PU), skin (SK) and seed membrane (SM) by 50, 95% ethanol and water (W). TK6 cells (1x10⁵ cells/ml) were pre-incubated with GAC extracts at various concentrations for 24 hours and followed by exposure to 50 µM H₂O₂ for 5 min. at 4°C. For the UV treatment, pre-treated cells were subsequently irradiated with a 254 nm UVC germicidal lamp. Following H₂O₂ and UVC treatments, cells were analyzed for DNA damage using the high alkaline (pH >13) comet assay. Two major parameters, i.e. distance of DNA migration (tail length, TL) and damaged DNA intensity (tail moment, TM) were determined by Comet III software. It found that H₂O₂ could significantly induce about 10-fold DNA damage over untreated DNA. Interestingly, this damage was suppressed by 30-60% when cells were pre-treated with PU, SK and SM extracts at 25, 50 and 100 µg m^-1. Regarding test condition used, UVC could clearly induce greater DNA damage in TK6 cells than that by H₂O₂. This might lead to a reduction in inhibitory effect of GAC extracts to 20-30% in UVC-treated cells. These suggest that GAC possesses DNA protective ability against H₂O₂ and UVC. The degree of anti-oxidative damage activity in TK6 human lymphoblast cells of GAC extracts is SK95>SMW>SK50.