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.
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.
Among the tested extracts, T. polium contained the highest percentage of RA (1.8%w/w) and exhibited the least toxicity (MNTC = 1000 μg/ml). The greatest anti-HSV-1 was shown by T. polium and Z. clinopoides extracts which exhibited both time and concentration-dependent plaque inhibition.