Chemical diversity in Mentha genus: GC-MS Profiling of essential Oils, polyphenol content analysis, and biological activity of Extracts

The genus Mentha, a prominent member of the Lamiaceae family, is known for its considerable chemical diversity, which underlies its diverse biological properties. The present paper investigates the chemical diversity of Mentha species, namely M. viridis, M. pulegium, M. longifolia, M. suaveolens subsp. timija, M. cervina, and M. aquatica, through gas chromatography-mass spectrometry (GC-MS) analysis of the composition of essential oils obtained by hydrodistillation. Additionally, ethanol-extracted plant samples were analyzed for their chemical content and biological potential. Total phenolic (TPC), flavonoid (TFC) and proanthocyanidin (TPAC) contents were determined using standard methods. Antioxidant activity was measured using the DPPH method and IC50 values were determined for each extract. Antimicrobial activity was evaluated by disc diffusion and microdilution methods against two Gram-positive bacterial species, two Gram-negative bacterial species, and two yeast species. High inter- and intraspecific diversity was observed in the essential oil compositions, which was attributed to genetic variation. Mint extracts were rich in polyphenols and flavonoids, with M. pulegium exhibiting the highest TPC (0.842 g GAE/g DW), TFC (0.82 g QE/g DW) and lowest IC50 value (9.693 µg/ml), indicating superior antioxidant activity. The extracts also exhibited strong antimicrobial activity at low concentrations, inhibiting Staphylococcus aureus (0.78-3.12 mg/ml), Staphylococcus epidermidis (1.56-6. 25 mg/ml), Pseudomonas aeruginosa (1.56-12.5 mg/ml), Salmonella enteritidis (3.12-25 mg/ml), Saccharomyces cerevisiae (7.81-50 mg/ml) and Candida albicans (9.37-50 mg/ml). These findings suggest that Mentha species, especially M. pulegium, have significant potential for use in natural antioxidant and antimicrobial applications