HUMIC SUBSTANCES AND MOISTURE CONTENT IN THE PRODUCTION OF BIOMASS AND BIOACTIVE CONSTITUENTS OF Th ymus vulgaris L.

Abstract

Thyme (Thymus vulgaris L.) is an aromatic and medicinal plant with antioxidant, antimicrobial and antinfungical properties that have attracted the interest of pharmacological and food industries. Humic substances (HS) are a natural product that has shown beneficial effects on soil and on plant growth. These positive effects are explained by the direct interaction of HS with physiological processes. But it is unknown their effect on the composition of the thyme bioactive constituents. To test the effect of humic substances, seeds of T. vulgaris were germinated and grown at different rates of HS (100, 200, 300 and 400 mg L^-1). Th yme plants were also grown at three levels of moisture (20, 40 and 60 % of field capacity). At harvest plant height and shoot fresh and dry weight were measured. Bioactive constituents were determined in terms of yield and principal components of essential oil (by distillation in Clevenger apparatus and gas chromatography). Antioxidant activity, total phenolic and flavonoid content were determined with spectrophotometric techniques. Morphological variables, except for shoot fresh weight, showed signifi cant differences (P ≤ 0.05) among treatments. The essential oil yield and composition, as well as antioxidant activity and total phenolic and flavonoid contents, were higher at the highest levels of HS and substrate moisture.