Isolation, antimicrobial evaluation, and in silico docking of spinasterol from Impatiens rothii Hook. f. tuber extract

Abstract

BACKGROUND: The increasing prevalence of drug-resistant infections highlights the need for new antimicrobial agents. Ethiopia's diverse plant resources remain largely underexplored, including Impatiens rothii tuber, an endemic species traditionally used to treat infections. This study therefore evaluated the antimicrobial activity of I. rothii tuber extract and its isolated compound, spinasterol. METHODS: Tuber extracts were prepared using 80% methanol and fractionated via silica gel chromatography to isolate spinasterol (1), identified by MS and NMR. Antimicrobial activity was tested against 26 bacterial and 4 fungal strains. Molecular docking assessed binding interactions with MRSA pyruvate kinase and sterol 14-alpha demethylase as antibacterial and antifungal targets, respectively. RESULTS: Both the extract and spinasterol (1) showed broad-spectrum antibacterial activity, with promising effects against Escherichia coli and Vibrio cholerae. Spinasterol (1) showed a minimum inhibitory concentration (MIC) of 25 µg/mL against non-resistant E. coli strains and V. cholerae, comparable to ciprofloxacin. Antifungal testing showed MIC values of 200 µg/mL against Candida albicans and 400 µg/mL against Aspergillus niger. Molecular docking revealed moderate binding of spinasterol (1) to MRSA pyruvate kinase (- 5.278 kcal/mol) and to sterol 14-alpha demethylase (- 8.523 kcal/mol), suggesting its antibacterial and antifungal mechanisms. CONCLUSIONS: This study demonstrates the antimicrobial activity of I. rothii extract and its constituent spinasterol, supporting its ethnomedicinal use. Spinasterol demonstrates promise as a potential antimicrobial scaffold; however, further optimization is necessary to enhance its antimicrobial efficacy. Additional experimental studies, including enzyme inhibition assays, are also needed to validate these predictive molecular findings.