Antimicrobial assessment and in-silico molecular docking of Azadirachta indica (Neem) leaf extracts on some Multidrug resistance clinical isolates

Abstract

Medicinal plants, as an effective source of traditional medicine, have genuine utility, and about 80% of the suburban population relies on plants as primary health care globally, especially in Africa, due to their availability and fewer complications. This study was designed to determine the antimicrobial effect of Azadirachta indica extracts in the context of G6PD deficiency and malaria co-infection on clinical isolates, comprising five (5) bacteria and four (4) fungi, using the agar well diffusion method. Minimum inhibitory and bactericidal concentration, including kinetic growth of the isolates, were determined by macrodilution and spectrophotometry methods. The aim of the study is to determine antimicrobial activities and phytochemical constituents of Azadirachta indica (Neem) on multidrug resistant clinical isolates. The phytochemical and functional group profiling in the extracts were performed using GC–MS standard method and Fourier-Transform Infrared (FTIR) spectrophotometry. In-silico molecular docking analysis of the bioactive compounds in neem extract and oil was determined by computational modelling tools and the molecular Auto Dock software. Data were analysed using one-way ANOVA to compare the mean levels of significance of the parameters, where the level of significance was set as (P <0.05), and Duncan Multiple Range Test (DMRT) was used to compare the significance between the groups. The results showed that aqueous neem demonstrates narrow antimicrobial potential, while methanol, including oil of neem extracts, displayed broad antimicrobial potential, and aqueous neem gave the strongest inhibitory zone of 14 mm against Escherichia coli. Neem extracts demonstrate broad antifungal potential over amphotericin B, while methanolic neem has a 0.60 mm wide inhibitory zone against Saccharomyces cerevisiae. The minimum inhibitory concentration and minimum bactericidal concentration for neem oil were 2.00 mg/ml stronger. Growth kinetics indicated bacteriostatic effects of neem extracts on Staphylococcus aureus, Escherichia coli, Candida albicans, and Aspergillus niger. Neem oil and powder contain 14 and 18 phytochemical profiles while α-D-Glucopyranose and n-Hexadecanoic acid were identified at the highest peak area of 21.98 % and 12.31% respectively. In-silico molecular docking identified diethylphthalate as a strong microbial protein inhibitor at -8.5 kcal, low binding energy with S aureus 1txt and E. coli 2ZIP proteins, while 9,17-octadecadienal (Z), methyl 10-methyl hexadecanoate, and oleic acid contributed to neem oil’s antibacterial activity with low binding energy of -8.00 kcal with S aureus 1txt and E. coli 2ZIP proteins. However, the therapeutic importance of neem in combating pathogenic microbes and their sustainability as an alternative medicine is significant. The findings of this research acknowledge and scientifically validate the use of plants against microbial pathogenic activities.