Phyllanthus orbicularis aqueous extract: cytotoxic, genotoxic, and antimutagenic effects in the CHO cell line.

The present work evaluates the cytotoxic, genotoxic, and antimutagenic effects of Phyllanthus orbicularis (plant of genus Phyllantus) aqueous extract in Chinese hamster ovary (CHO) cells. P. orbicularis aqueous extracts are used in Cuban traditional medicine for their antiviral activity against Hepatitis B virus and A and B flu virus. The cytotoxicity of the extract was tested by means of colony-forming ability and growth-inhibition assays as well as by measuring the mitotic index. Apoptosis induction and cell-cycle kinetics were analyzed by cytofluorimetric methods. Chromosome aberration assays were performed to study the genotoxic and antimutagenic activity of the extract. Results show that doses of up to 100 microg/ml of the extract did not induce any cytotoxic effects. Cell survival and mitotic index decreased significantly at doses higher than 100 microg/ml as a function of dose as well as of treatment time. Moreover, continuous treatments of up to 18 h induced the appearance of a significant number of apoptotic cells. Following a 3-h exposure to a dose of 750 microg/ml, cells accumulated significantly in G(2)-M phase and remained blocked in G(1-) and G(2)-M phases after several posttreatments in fresh growth medium. The aqueous extract alone did not induce chromosome aberrations but, in combined treatment with H(2)O(2), significantly reduced H(2)O(2)-induced chromosome aberrations. Flow cytometric analysis of DCFH intracellular oxidation showed that the extract decreased the oxidizing power of H(2)O(2.) This ability could possibly explain the extract's antigenotoxic activity. Absence of cytotoxicity at the lower tested doses and the antimutagenic properties of the extract stimulate the interest in studying possible new pharmaceutical uses of P. orbicularis. Copyright 1999 Academic Press.