In vitro activity of Phyllanthus (Euphorbiaceae) species against the DNA polymerase of hepatitis viruses: effects of growing environment and inter- and intra-specific differences.
Extracts of P. amarus are known to reduce or eliminate detectable hepatitis B virus surface antigen in humans or woodchuck hepatitis virus surface antigen in woodchucks (Marmota monax). A series of experiments was conducted to evaluate the in vitro inhibition of viral DNA polymerase (DNAp) among different species of Phyllanthus and within the most promising species, and to evaluate differences in activity that might be correlated with environmental effects. There were significant differences between species in DNAp inhibitory activity, the most active species being P. mimicus. There were also significant differences in activity among P. urinaria seed sources, but not among P. amarus seed sources. There were significant differences between plants in one seedlot of P. amarus, but clear-cut heritable differences were not established. DNAp inhibitory activity was generally unaffected by soil fertility, moisture, pH or Ca level, but was affected by temperature. Except for temperature, environmental effects were of a lesser magnitude than genotypic effects. Cultivation of P. amarus had no effect on DNAp inhibition compared with material gathered from the wild.