Evaluation of Antioxidant, Cholinesterase Inhibitory and Antimicrobial Properties of Mentha longifolia subsp. noeana and Its Secondary Metabolites

The aim of the present study was to determine the chemical structures of the isolated compounds, the essential oil and fatty acid compositions of Mentha longifolia subsp. noeana with their biological activities. Ursolic acid (1), uvaol (2), stigmast-5-ene-3-yl formate (3), stigmast-5-en-3-one (4), -sitosterol (5), bis(2ethylhexyl) benzene-1,2-dicarboxylate (6), hexacosyl (E)-ferulate (7) and 5-hydroxy-6,7,3',4'-tetramethoxy flavone (8) were obtained from the aerial parts. The compounds (2-4, 6, 7) were isolated for the first time from a Mentha species. Palmitic acid (40.8%) was the major component of the non-polar fraction obtained from the petroleum ether extract. Pulegone (32.3%) was the main constituent of the essential oil which exhibited strong butyrylcholinesterase inhibitory activity (77.36 ± 0.29%), moderate antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Candida albicans. The methanol extract showed 80% inhibition of lipid peroxidation, and the acetone extract possessed moderate DPPH free radical scavenging activity (60% inhibition) at 100 g/mL.