|
As a preliminary experiment to investigate the antitumor activity of colored rice in vivo, inhibitory effect of solvent extracts from colored rice brans on DNA strand scission and tumor promotion was examined in vitro. Two colored rice cultivars, Sanghaehyanghyulla and Suwon 415 were compared with Chuchung as a control. The antimutagenic activity of each rice cultivars increased in order of Chuchung$lt;Sanghaehyanghyulla$lt;Suwon 415. However, the inhibitory activity of 70% ethanolic extracts against DNA strand scission increased in order of Sanghaehyanghyulla$lt;Chuchung$lt;Suwon 415. The results from the examination on the chloroform fractions demonstrated that Sanghaehyanghyulla did not show any significant inhibitory activity, and that Chuchung was unexpectedly somewhat more inhibitory than Sanghaehyanghyulla. Strong inhibition against DNA strand scission was observed in the chloroform fraction of Suwon 415, activity of which was almost same as that of the 70% ethanolic extract(about 50% inhibition). We also measured the inhibitory effect of 70% ethanolic extracts on tumor promotion by means of its actions that block the expression of Epstein-Barr virus early diffusible antigen induced by tumor promotor, indicating the increase of inhibitory activity in order of Chuchung$lt;Sanghaehyanghyulla$lt;Suwon 415. Although every chloroform fractions showed complete blockage of tumor promotion, Suwon 415 was found to be the only cultivar that showed the cytotoxicity-free antipromotion effect.
|