Inhibition of hepatitis B surface antigen secretion on human hepatoma cells. Components from Rubia cordifolia.

The antiviral activity in the roots of Rubia cordifolia was examined, and three naphthohydroquinones, furomollugin (1), mollugin (2), and rubilactone (3), were isolated from it. Compounds 1 and 2 strongly suppressed the secretion of hepatitis B surface antigen (HBsAg), both with IC50 = 2.0 micrograms/mL, in human hepatoma Hep3B cells while having little effect on the viability of the cells. Evaluation of structurally related derivatives of 1 and 2 revealed that a 6-hydroxy group and a pyran or furan ring contribute to this suppressive effect.