Anticancer and antiviral activities of Youngia japonica (L.) DC (Asteraceae, Compositae).

Aqueous and ethanol extracts of Youngia japonica (also known as Oriental hawksbeard) were tested in vitro for anti-tumor activity against three cell lines, human promyelocytic leukaemia (HL-60), human myelogenous leukaemia (chronic K-562) and mouse Sarcoma 180 (S-180), and for antiviral activity against respiratory syncytial virus (RSV), influenza A virus (Flu A) and herpes simplex virus type 1 (HSV-1) by cytopathic effect (CPE) reduction assay. Hot water extract of Youngia japonica inhibited cell proliferation and growth of all cancer cell lines to various extent. K-562 cells were the most sensitive to the extract whereas S-180 cells were the least. It did not show any significant cytotoxic effects on normal mammalian Vero cells up to the concentration of 450 microg/mL. The ethanol extract of whole plant of Youngia japonica exhibited antiviral activity against RSV cultured in HEp-2 cells, but did not have any activity against Flu A and HSV-1. Two partially purified fractions (Fr.10 and Fr.11) from the 95% ethanol extract exhibited significant anti-RSV with 50% inhibitory concentration (IC50) in the range of 3.0-6.0 microg/mL. The ratio of the viral titer reduction in the absence (viral control) and presence of the maximal non-cytotoxic concentration (MNCC) of the Fr.10 and Fr.11 was both estimated to be 1 x 10(4) (RF, viral titer reduction factors), indicating that their anti-RSV activity was high enough to justify for further analysis. Our preliminary analysis showed that the antiviral ingredients were likely to contain phenolic compounds including tannins by chemical tests.