Aim To investigate the HIV-1 entry inhibitory activities of myriceric acid B and C isolated from Rhoiptelea chiliantha Diels et Hand-Mazz and their mechanism of action.Method The plasmids encoding envelope proteins of HIV-1 (pHXB2) and VSV (pVSV-G) were cotransfected 293T cells with pNL4-3.Luc.R-E- to produce HIV-1 Env pseudovirus and VSV-G pseudovirus,respectively,which were used for testing the antiviral activities of these compounds.ELISA and molecular docking were used to study the mechanism of action of the active compounds.Results Myriceric acid B could significantly inhibit the infection of HIV-1 Env pseudovirus with an IC_(50) of(8.3±0.2)mg·L~(-1).The carbonoxyl group at C-28 position and the hydroxyl group at the C-3 position of myriceric acid B are important for its anti-HIV-1 activity.Like other HIV-1 entry inhibitors targeting gp41 (eg,ADS-J1 and NB-64), myriceric acid B could also block the gp41 six-helix bundle formation.Molecular docking analysis suggests that myriceric acid B may bind to the hydrophobic cavity of the gp41 N-trimeric coiled coil.Conclusion Myriceric acid B is a potent HIV-1 entry inhibitor targeting gp41 and can serve as a lead compound for developing novel anti-HIV-1 drug.

Aim ADS-J1 is a low molecular HIV entry inhibitor targeting HIV transmembrane subunit gp41 through virtual screening from a compound library containing 20 000 molecules.This study is to investigate the binding sites of ADS-J1 on gp41.Methods Acid native polyacrylamide gel electrophoresis (AN-PAGE) assay was applied to test the binding ability of ADS-J1 with the peptides derived from gp41 N-terminal heptad repeat (NHR) region.Results It was reported previously that ADS-J1 could block the gp41 six-helix bundle (6-HB) formation using native polyacrylamide gel electrophoresis (N-PAGE).However,the binding sites could not be found because positive charged N-peptides derived from gp41 NHR could not show bands on the gel.In the present study,the AN-PAGE assay which could show N-peptides in the gel was established,and it was found that ADS-J1 could inhibit the gp41 6-HB formation.Moreover,ADS-J1 bound directly to the gp41 cavity region of NHR.The positively charged residue (K574) located in this region was critical for the binding of ADS-J1.Conclusions ADS-J1 inhibits HIV entry by targeting the cavity region of gp41 NHR,whereas K574 in the cavity plays a critical role for the binding.Furthermore,the AN-PAGE assay provides a simple method for studying the mechanism of action of virus entry inhibitors targeting the transmembrane protein of type I enveloped virus.