Anti-respiratory syncytial virus activity of clove extract

Abstract

Abstract Background Natural products have been used by humans for thousands of years for healing purposes. They occasionally resulted in the development of research-proven new drugs. A well-known example of such a drug is the malaria medicine artemisinin isolated from the plant sweet wormwood. Respiratory syncytial virus (RSV) is an RNA virus that belongs to Paramyxoviridae family and is known for causing severe respiratory infections in new-borns and elderly. As of today, there is still no registered drug available against this important virus nor a vaccine for its prevention. With lack of effective antiviral therapy, treatment of acute RSV mainly involves supportive care. Aim To investigate whether any specimen of a collection of traditional medical plants exhibits antiviral activity against RSV in cell culture. Methods A collection of traditional medical plant was pulverized and extracted with sterile water to be screened for antiviral effect against RSV. The hit plant, a clove flower bud, was studied in more details to determine its anti-RSV potency, toxicity for HEp-2 cells, and the mechanism of antiviral activity. Results Out of several plants examined only clove extract showed anti-RSV activity. This activity was manifested by inhibiting RSV infection of HEp-2 cells with IC50 value of 102 μg/ml and reducing, at 2000 μg/ml, the viral yield by ~10000 times. The activity was highly selective for RSV and directly targeted the free RSV particles infectivity during early step of viral infections. Conclusions Clove extract showed a potent anti-RSV activity that appeared to be virucidal. Further extension of these studies based on identification of active ingredients of clove extract is warranted for its development as anti-RSV drug or as an air disinfectant.