Flavonoid baicalin inhibits HIV-1 infection at the level of viral entry

Baicalin (BA) is a flavonoid compound purified from medicinal plant Scutell aria baicalensis Georgi and has been shown to possess anti-inflammatory and anti-HIV-1 activities. In an effort to elucidate the mechanism of the anti -inflammatory effect of BG we recently found that this flavonoid compound w as able to form complexes with selected chemokines and attenuated their cap acity to bind and activate receptors on the cell surface. These observation s prompted us to investigate whether BA could inhibit HIV-1 infection by in terfering with viral entry, a process known to involve interaction between HIV-1 envelope proteins and the cellular CD4 and chemokine receptors. We fo und that BA at the noncytotoxic concentrations, inhibited both T cell tropi c (X4) and monocyte tropic (R5) HIV-1 Env protein mediated fusion with cell s expressing CD4/CXCR4 or CD4/CCR5, Furthermore, presence of BA at the init ial stage of HIV-1 viral adsorption blocked the replication of HIV-1 early strong stop DNA in cells. Since BA did not inhibit binding of HIV-1 gp120 t o CD4, we propose that BA may interfere with the interaction of HIV-1 Env w ith chemokine coreceptors and block HIV-1 entry of target cells, Therefore, BA can be used as a basis for developing novel anti-HIV-l agents.