Effects of cultivation and application of inorganic fertilizer on volatile oils constituents and biological properties of Thymus leptobotrys Murb. and T. maroccanus Ball. from Morocco

Thymus leptobotrys and T. maroccanus are endemic Moroccan medicinal species that are intensively exploited from the wild because of their wide ranging therapeutic properties. In order to preserve these valuable medicinal plants from risk of extinction, the cultivation (with and without N, P, and K fertilizer) and its consequent effect on oil chemical composition and biological activities were studied. Carvacrol (64.1–78.1%) was found as the major constituent in oil samples, followed by p-cymene (4.7–12.4%) and γ-terpinene (3.2–7.9%). Cultivation without using N, P, and K fertilizer caused a slight decrease in carvacrol content against an increase of its main precursor p-cymene. However, application of N, P, and K fertilizer increased the carvacrol content of 3.9% for T. maroccanus and 9.4% for T. leptobotrys oils compared with unfertilized plants. Regarding the antioxidant activity, wild thyme oils showed the highest potency in all assays, while oils from cultivated plants fertilized with N, P, and K had greater activity than oils from plants not receiving fertilizer. Concerning the antimicrobial activity, oils from fertilized plants exhibited the highest inhibitory effect against most tested strains with MIC values ranged from 0.03 to 31.68 mg/mL. From this work, it can be concluded that cultivation could be a promising solution to ensure the sustainable utilization of these endemic and threatened medicinal thyme species.