Anti-herpes simplex virus component isolated from Maclura cochinchinensis.

The powerful anti-herpes simplex virus (HSV) activity of Maclura cochinchinensis in vitro prompted us to carry out biologically-guided separation of the active component(s). Ethyl acetate and methanol extracts exhibited anti-HSV-2 activity at EC50 values of 38.5 micrograms/ml and 50.8 micrograms/ml, respectively. Although petroleum ether extract was inactive, a chloroform extract was too toxic to the test cell culture to perform the test. Biologically-guided chromatographic separation of the ethyl acetate extract yielded compound A, identified as morin using a spectroscopic method. Morin exhibited anti-HSV-2 activity at an EC50 value of 53.5 micrograms/ml. Morin pentaacetate was synthetized, but was inactive. This result suggested that free hydroxyl groups are required for anti-HSV-activity, as demonstrated previously for the antiviral activity of other flavonoids.