Effect of naringenin on the replication of herpes simplex virus

Antiviral activities of naringenin against herpes simplex viruses type 1 (HSV-1) strain KOS and type 2 (HSV-2) strain Baylor 186 on Vero cells using plaque reduction, inactivation, and prophylactic assay were investigated. Naringenin exhibited anti-HSV activity in all assays. The 50% inhibitory concentrations (IC₅₀) of naringenin against HSV-1 were 46.64±7.06, 43.30±2.80, and 36.08±1.86 µg/ml, respectively, and the selective index (SI) were 7.07, 7.61, and 9.12, respectively. In the inhibition of HSV-2, IC₅₀ values were 48.27±5.14, 47.58±5.24 and 39.39±1.68 µg/ml, respectively, and SI of 6.83, 6.93 and 8.36 were observed in naringenin treatment. The cytotoxic concentration of naringenin that inhibited cell growth 50 % (CC₅₀), in trypan blue exclusion and MTT reduction assays, were more than 500 µg/ml at 24 h, 329.01±33.37 and 378.71±25.25µg/ml at 48 h and 305.37±18.36 and 304.56±7.41 µg/ml at 72 h, respectively. In addition, possible mechanism of action of naringenin against HSV-1 was determined using virus yield inhibition assay, required treatment period for inhibition of plaque formation, adsorption, penetration, virucidal and combined effect of naringenin with acyclovir on plaque formation. The results indicated that naringenin inhibited virus adsorption to cell surface and did directly inactivate virus particle. Furthermore, the synergistic anti-herpes simplex effect of naringenin was observed when combined with acyclovir. This study indicated that naringenin showed anti-herpes simplex activity and was the promising anti-herpetic agent.