The aims of this study were to investigate the cytotoxic and genotoxic activities of an aqueous extract from Thai Noni’s leaf (ANL) in human lymphocytes in vitro. Chromosome aberration and sister chromatid exchange (SCE) assays were performed. Treatment of ANL (0.8-25 mg/ml) for 3 h did not significantly induce chromosomal aberration nor SCEs (p<0.05). Nevertheless, ANL could induce cytotoxic activities as shown by their toxic level of mitotic index in a dose dependent manner. Only toxicity induced at lower doses of ANL (< 3.1 mg/ml) could be recovered as shown by their normal level of the proliferation index. ANL at higher dose of 50 mg/ml induced potent cytotoxicity as no mitotic cell was found. Interestingly, metaphase chromosomes undergoing tetraploidization were found from ANL treatment at 12.5 and 25 mg/ml. These indicate that ANL treatment could interrupt cell cycle that progressed after S phase. Therefore, the optimum dose of ANL as food supplement needs to be considered carefully for human safety. Nevertheless, ANL at doses lower than 3.1 mg/ml might be useful for treatment of human hyperproliferative disorder at appropriate dose since ANL could induce temporary cytotoxicity without genotoxicity. Scientific study is also needed to verify the usefulness of an aqueous extract of Noni’s leaf.
