In vitro Antiviral Activity of the Aqueous Extract and Essential Oil of Ocimum gratissimum L. Leaves against the West Nile Virus

Abstract

Aims: The emergence of viral infections highlights the urgent need to develop new antiviral molecules. This study is part of an effort to explore the antiviral properties of medicinal plants used in traditional pharmacopoeia in Côte d'Ivoire. The main objective was to evaluate the antiviral activity of the essential oil and aqueous extract of Ocimum gratissimum leaves against the West Nile virus. Study Design: An in vitro experimental study carried out to evaluate the cytotoxicity and antiviral activity of the essential oil and aqueous extract of Ocimum gratissimum leaves against West Nile virus using Vero cell cultures. Place and Duration of Study: The study was conducted at the Epidemic Viruses Department of Institut Pasteur de Côte d’Ivoire and at the Biochemical Pharmacodynamics Unit of Félix Houphouet Boigny University over a period of six months. Methodology: After determining the safety of the different dilutions of the extracts by a cytotoxicity test on Vero cells, we used non-toxic concentrations of the essential oil and aqueous extract of Ocimum gratissimum to perform tests to inhibit the replication of the West Nile virus. Results: The cytotoxicity study showed that the essential oil has lower toxicity than the aqueous extract, with respective CC50 values of 500 µg/ml and 250 µg/ml. Ocimum gratissimum essential oil inhibited the growth of West Nile virus, with a minimum inhibitory concentration of 250 μg/ml, while the aqueous extract showed no antiviral effect. Conclusion: Thus, Ocimum gratissimum essential oil has shown promising antiviral activity against the West Nile virus, probably due to the phytochemical compounds it contains.