Abstract
This study investigated the antiviral activity of betacyanins from red pitahaya (Hylocereus polyrhizus) and red spinach (Amaranthus dubius) against dengue virus type 2 (DENV-2). The pulp of red pitahaya and the leaves of red spinach were extracted using methanol followed by sub-fractionation and Amberlite XAD16N column chromatography to obtain betacyanin fractions. The half maximum cytotoxicity concentration for betacyanin fractions from red pitahaya and red spinach on Vero cells were 4.346 and 2.287 mg ml(-1), respectively. The half-maximal inhibitory concentration (IC(50)) of betacyanin fraction from red pitahaya was 125.8 μg ml(-1) with selectivity index (SI) of 5.8. For betacyanin fraction from red spinach, the IC(50) value was 14.62 µg ml(-1) with SI of 28.51. Using the maximum non-toxic betacyanin concentration, direct virucidal effect against DENV-2 was obtained from betacyanin fraction from red pitahaya (IC(50) of 126.70 μg ml(-1); 95.0 % virus inhibition) and red spinach (IC(50) value of 106.80 μg ml(-1); 65.9 % of virus inhibition). Betacyanin fractions from red pitahaya and red spinach inhibited DENV-2 in vitro.