Anti-HIV activity of dibenzylbutyrolactone-type lignans from Phenax species endemic in Costa Rica

Previously, we isolated two new dibenzylbutyrolactone‐type lignans, named phenaxolactones 1 and 2, from the leaves of Phenax angustifolius Wedd. (Urticaceae). In this investigation three new dibenzylbutyrolactone lignans (phenaxolactones 3–5), together with phenaxolactone 1, and flavones vitexin (6), isovitexin (7), were isolated from Phenax rugosus Wedd. leaves collected in Santa Ana, Costa Rica. The structures were elucidated using 1D and 2D NMR spectroscopy as well as mass spectrometry. Phenaxolactones 1–5 and flavones 6 and 7 were evaluated for their inhibitory activity against HIV‐1MN in infected C8166 cells. The most promising compound was phenaxolactone 1 with an EC50 value of 3.0μM, no cytotoxicity at 112μM and a therapeutic index value of 37.3.