Anti-human immunodeficiency virus activity of oligosaccharides from rooibos tea (Aspalathus linearis) extracts in vitro.

The active substances, acid polysaccharides, were extracted with 1% sodium hydroxide from the leaves of rooibos tea (Aspalathus linearis), Du Zhong Cha (Eucommia ulmoides Oliv.) and Japanese tea leaves (Camellia sinensis var. sinensis). The alkaline extracts of Rooibos tea and Du-Zhong tea leaves, but not Japanese tea leaves suppressed the HIV-induced cytopathicity using HIV (HTLV-III) infected MT-4 cells, having extremely low cytotoxicity: Its 50% effective concentration (EC50) was 12-67 micrograms/mL, white 50% cytotoxic concentration (CC50) was higher than 1.0 mg/mL. The active substances were purified with ethanol precipitation. The substances were composed of 27% of reducing sugar, 46% of neutral sugars and 22% of uronic acid. A LD50 of the alkaline extracts from rooibos tea was higher than 1.2 g/kg body weight. Acid degradated substances composed of disaccharides and trisaccharides, were also suppressed the HIV-induced cytopathicity. From these results, it is probable that acid polysaccharides from rooibos tea were extremely safe, and that HIV infection may be suppressed by daily intake of the alkaline extracts of rooibos tea and Du-Zhong tea.