Bioactivity-guided fractionation of Phyllanthus orbicularis and identification of the principal anti HSV-2 compounds

The antiherpes virus properties of Phyllanthus orbicularis Kunth, a Cuban-endemic medicinal plant, have been reported previously but data on its phytochemical profile and identification of antiviral metabolites as well as their mechanisms of action are still lacking. In this work, a bioactivity-guided phytochemical analysis was performed in order to isolate anti HSV-2 compounds. P. orbicularis contained mainly phenolic acids derivatives and flavonoids. The antiviral effects were attributed to (-)-epicatechin-3-O-gallate (EC(50) = 11.7 µg/mL), procyanidins B1 and B2 (EC(50) = 32.8 µg/mL and 24.2 µg/mL, respectively) as well as oligomeric and polymeric procyanidins and their gallate derivatives. The antiviral mechanisms of the active P. orbicularis extracts and fractions were also investigated and the inhibition of several HSV-2 early replication events and DNA synthesis were observed. This is the first study of extensive fractionation and phytochemical characterization of phenolic compounds from this species.