Essential oil composition and total phenolic, flavonoid contents, and antioxidant activity of sage (Salvia officinalis L.) extract under chitosan application and irrigation frequencies

Sage (Salvia officinalis L.), which is one of the most important pharmaceutical herbs, has been exploited for many uses. It is an important industrial crop that natural products in the form of extracts and essential oil from the leaves of this herb are used in pharmaceutical, perfumery, and food industries. Response of sage to foliar application of chitosan (control, 0.0, 0.25 and 0.50 g/L), a marine polysaccharide with unique bioactive properties, under three irrigation frequencies (4, 6, and 8 every days) was evaluated in an experimental field at semiarid and cold climate, Southwestern of Iran. Chitosan and irrigation frequencies treatments had significant effects on studied parameters, including quantity and quality of essential oil, antioxidant activities, and the amounts of total phenolic and flavonoids of the extract of sage. The results clearly indicated that application of chitosan was beneficial to plants under deficit irrigation treatments. The foliar application of chitosan reduced the adverse effect of reduced irrigation on essential oil yield and improved content of the essential oil. Elicitation of sage with chitosan had positive influences on the amounts of secondary metabolites, such as alpha-pinene, beta-pinene, limonene, alpha-thujone, beta-thujone, camphor, and 1,8-cineole in the essential oil from sage under reduced irrigation. In reduced irrigation conditions, the antioxidant activity, and the amounts of total phenolic and flavonoid of the extracts increased when the plants were sprayed with chitosan. In conclusion, results of this study indicated that the spray of chitosan elicitor can be have useful impacts on the essential oil quality and quantity, antioxidant activity, and the amounts of total phenolic and flavonoid of sage under reduced irrigation conditions or drought stress.