Biflavonoids such as
amentoflavone (1),
agathisflavone (2),
robustaflavone (3),
hinokiflavone (4), volkensiflavone (5), rhusflavanone (7), succedaneflavanone (9), all isolated from Rhus succedanea and Garcinia multiflora, as well as their
methyl ethers and
acetates, volkensiflavone hexamethyl
ether (6), rhusflavanone hexaacetate (8), and succedaneflavanone hexaacetate (10) were evaluated for their
antiviral activities. The inhibitory activities against a number of viruses including respiratory viruses (
influenza A,
influenza B, respiratory syncytial,
parainfluenza type 3, adenovirus type 5, and
measles) and herpes viruses (HSV-1, HSV-2, HCMV, and VZV) were investigated. The results indicated that
robustaflavone exhibited strong inhibitory effects against
influenza A and influenza B viruses with EC50 values of 2.0 micrograms/ml and 0.2 microgram/ml, respectively, and selectivity index values (SI) of 16 and 454, respectively.
Amentoflavone and
agathisflavone also demonstrated significant activity against
influenza A and B viruses.
Amentoflavone and
robustaflavone exhibited moderate anti-HSV-1 anti-HSV-2 activities with EC50 values of 17.9 micrograms/ml (HSV-1) and 48.0 micrograms/ml (HSV-2) and SI values of > 5.6 (HSV-1) and > 2.1 (HSV-2) for
amentoflavone; EC50 values of 8.6 micrograms/ml (HSV-1) and 8.5 micrograms/ml (HSV-2), and SI values of > 11.6 (HSV-1) and > 11.8 (HSV-2) for
robustaflavone. Rhusflavanone demonstrated inhibitory activities against
influenza B,
measles, and HSV-2 viruses with SI values of 9.3, 8 and > 6.4, respectively. Succedaneaflavanone exhibited inhibitory activities against influenza B virus and VZV with SI values of 15 and < 3.0, respectively.