In vitro evaluation of anti-herpes simplex-1 activity of three standardized medicinal plants from Lamiaceae

Background: Rosmarinic acid (RA) is a phenolic acid with antioxidant and anti-viral effects. We have studied anti-herpes simplex virus type 1 (HSV-1) effect of three medicinal plants from Lamiaceae family which have been standardized on the basis of RA content. Materials and Methods: Methanolic extract of Teucrium polium, Ziziphora clinopoides, and Salvia rhytidea was prepared by maceration method and RA content of the plants was determined using a spectrophotometric method. Maximum nontoxic concentration (MNTC) of the extracts was determined using neutral red method. Serial dilutions of extracts up to MNTC were examined on Vero cells for anti-HSV-1 effect by plaque assay in comparison to acyclovir as a positive control. Results: Among the tested extracts, T. polium contained the highest percentage of RA (1.8%w/w) and exhibited the least toxicity (MNTC = 1000 mu g/ml). The greatest anti-HSV-1 was shown by T. polium and Z. clinopoides extracts which exhibited both time and concentration-dependent plaque inhibition. Conclusion: Considering the low toxicity and significant anti-viral effect of T. polium extract, this plant would prove valuable as an active anti-viral drug.