Change in Content and Chemical Composition of Hypericum perforatum L. Oil at Three Harvest Time

Abstract

ABSTRACT St. John's wort is an important medicinal plant that contained a wide range of secondary metabolites such as naphthodianthrones, phloroglucinols and essential oil. The quality of Hypericum perforatum was determined by several cultural practices. In this research essential oil content and composition determined at before flowering, full flowering and fruit set stages. Water distillation was used for essential oil extraction. Essential oil composition was determined by GC and GC/MS. On the basis of the results herb of Saint John's wort in full flowering stage has higher amount of essential oil (0.35 ml/100 g dry weight) than before flowering and fruit set stage (0.12 and 0.16 ml/100 g dry weight, respectively). The essential oil contains longifolene, α- and γ-eudesmol, spathulenol, bicyclogermacrene, β-caryophyllene, α-cadinol, α-cadinene and β-bisabolene as major constituents. These constituents are affected by harvest time. In this respect longifolene is identified in oil sample before flowering and at fruit set stage (18.71 and 21.99%, respectively) but unidentified in the oil of full flowering stage. The amount of bicyclogermacrene was the highest (16.93%) at full flowering stage and decreased sharply at other harvest time. According to the results the most suitable time for harvesting of Hypericum perforatum with respect to essential oil content and composition is full flowering.