Abstract
ETHNOPHARMACOLOGICAL RELEVANCE: A catastrophic outbreak of severe acute respiratory syndrome (SARS-CoV-2; Coronavirus disease-19; COVID-19) was first detected in Wuhan, Hubei Province, China, in December 2019. Many experimental and clinical studies have focused on the effectiveness of medicinal plants such as Nigella sativa (NS) in combating SARS-CoV-2. In this study, we aimed to evaluate the in vitro effect of NS seed extract on SARS-CoV-2 spike protein (S1)-angiotensin-converting enzyme 2 (S-ACE2) interaction. MATERIALS AND METHODS: NS seed extracts used for the assay were prepared in chloroform, ethanol, and water by Soxhlet extraction and recovered by rotary evaporation. The inhibition percentage of S1-ACE2 interaction was analyzed using ELISA-SARS-CoV-2 S1 Protein-ACE2 Binding Inhibitor Screening Kit. Chemical finger-printing of the extracts was done using RP-HPLC. RESULTS: Significant concentration-dependent inhibition of the S1-ACE2 interaction was observed with chloroform, ethanol, and water extracts, ranging from 0.01 to 10 mg/ml. The P-values for the extracts were as follows: 0.0055, 0.0937, 0.0013, and 0.0003 for chloroform extract; 0.0876, 0.0703, 0.0183, and 0.0071 for ethanol extract; and 0.0915, 0.0312, 0.0006, and 0.0006 for water extract. The 50% inhibitory concentration (IC50) was determined to be 0.132 mg/ml, 0.288 mg/ml, and 4.06 mg/ml for chloroform, ethanol, and water extracts, respectively. CONCLUSION: The in vitro analysis utilizing SARS-CoV2 spike (S1) and ACE2 proteins proved that NS seed extracts have the potential to inhibit the S-ACE2 interaction, which warrants further studies that could lead to potential drug discovery for SARS-CoV2 infection.