Rosemary and neem methanolic extract: antioxidant, cytotoxic, and larvicidal activities supported by chemical composition and molecular docking simulations

Abstract

This study aimed to employ GC–MS to assess the chemical composition of MeOH leaf extracts of R. officinalis and A. indica and evaluate their insecticidal, antioxidant, and antibacterial activities. Twelve components, representing 98.61% and 100% of the total volatile compounds, were deduced from the extracted R. officinalis and A. indica, respectively, using this method. In R. officinalis extract, limonene is typically positioned as the main component (23.03%), while the main chemicals identified in A. indica extract were methyl (E)-octadec-13-enoate (23.20%) and (2R)-1,3,8-trimethyl-4-propyl-5-ethyl-2-(1-hydroxyethyl)-7-methoxycardonylethyl-6-methylenecarbonyl-porphyrin (23.03%). Both extracts of R. officinalis and A. indica exhibited different toxicity against the stored grain pest T. castaneum, with LC50 values of 1.470 and 2.588 mg/ml, respectively. Additionally, after 4 and 5 h of treatment at a concentration of 0.2 mg/ml, the A. indica extract showed the highest levels of repellent action (81.4% and 93.4%), and the R. officinalis extract showed a good repellent rate (64.9% and 80.7%) against T. castenum larvae. With an IC50 value of 35.83 and 28.68 mg/L and a radical scavenging activity percentage of 67.76% and 72.35%, the leaf extract was found to be the most potent plant extract when tested for DPPH antioxidant activity. Overall results showed that MeOH extracts of R. officinalis and A. indica were more effective against S. aureus than E. coli. To determine how the investigated chemicals attach to the active sites of E. coli DNA gyrase A and S. aureus undecaprenyl diphosphate synthase, docking studies were carried out. The consensus score analysis showed that limonene exhibits the best binding energy with both enzymes in docking analysis and more stability in molecular dynamics simulations. The RMSD was obtained at 20.6 and 4.199 (Kcal/mole). The two compounds were successfully used in molecular dynamics simulation research to generate stable complexes with DNA gyrase A.