Changes in the properties of Mentha spicata L. essential oil under the influence of soil characteristics, available water, and altitude in the mountainous regions of Kashan

Mentha spicata L. (Persian: Naana Dashti) is a medicinal plant traditionally used to treat respiratory and digestive disorders. Given its industrial importance and complex chemical profile, this study investigates how environmental factors are associated with the essential oil yield, chemical composition, and antibacterial activity of M. spicata in the mountainous regions of Kashan (Barzok, Hosnarood, Kamoo, and Viduj). Essential oils were extracted via a Clevenger-type apparatus and analyzed by GC–MS. Antibacterial efficacy was assessed using the agar well diffusion (D IZ ), MIC, and MBC methods. Results indicated that the highest essential oil yield occurred in Hosnarood (5.04%) and the lowest in Kamoo (1.08%), correlating with the lowest and highest altitudes and Plant Available Water (P.A.W) levels, respectively. Carvone was the predominant constituent in Viduj (63.98%), Hosnarood (54.45%) Kamoo (47.01%), and Barzok (46.85%), which showed a relationship with altitude variations. The essential oil from Barzok showed the strongest inhibition against Bacillus subtilis (12 mm), while Kamoo's oil was most effective against Escherichia coli (9.5 mm), both exhibiting relatively strong activity compared to Rifampin. In conclusion, altitude, water availability, and soil properties are significantly associated with the essential oil profile and biological potency of M. spicata , highlighting the importance of habitat selection for optimizing high-quality production.