Bioactive 2-(Methyldithio)Pyridine-3-Carbonitrile from Persian Shallot (Allium stipitatum Regel.) Exerts Broad-Spectrum Antimicrobial Activity

Abstract

Antibiotic resistance is a problem that continues to challenge the healthcare sector, especially in clinically significant pathogens like methicillin-resistant <i>Staphylococcus aureus</i> (MRSA). Herein is described the isolation and structure elucidation of a bioactive compound from <i>Allium stipitatum</i> with antimicrobial activity. Crude <i>Allium stipitatum</i> dichloromethane extract (ASDE) was subjected to systematic purification by chromatographic procedures to afford various bioactive fractions. A fraction that exhibited anti-MRSA activity (4 µg·mL^-1) was further characterized to determine the structure. The structure of the compound was elucidated as 2-(methyldithio)pyridine-3-carbonitrile (2-Medpy-3-CN). The 2-Medpy-3-CN compound, which was screened for antimicrobial activity, exhibited minimum inhibitory concentrations (MICs) in the range of 0.5 to >64 µg·mL^-1 for tested bacterial species and 0.25 to 2 µg·mL^-1 for <i>Candida</i> spp. Further studies are important to confirm the drug target and mechanism of action.