Inactivation of HSV-1 and HSV-2 and prevention of cell-to-cell virus spread by Santolina insularis is essential oil

The essential oil obtained in toto from Santolina insularis was investigate d for its antiviral activity on herpes simplex type 1 (HSV-1) and type 2 (H SV-2) in vitro. The IC50 values, determined by plaque reduction assays, wer e 0.88 and 0.7 mug/ml for HSV-1 and HSV-2 respectively, while the CC50 dete rmined by the MTT test on Vero cells was 112 mug/ml, indicating a CC50/IC50 ratio of 127 for HSV-1 and 160 for HSV-2. Results obtained by plaque reduc tion assays also indicated that the antiviral activity of S. insularis was principally due to direct virucidal effects. Antiviral activity against HSV -1 and HSV-2 was not observed in a post-attachment assay, and attachment as says indicated that virus adsorption was not inhibited. Up to 80% inhibitio n of HSV-1 was achieved at the concentration of 40 mug/ml by yield reductio n assay. Furthermore, reduction of plaque formation assays also showed that S. insularis essential oil inhibits cell-to-cell transmission of both HSV- 1 and HSV-2. (C) 2000 Elsevier Science B.V. All rights reserved.