Optimisation of supercritical carbon dioxide extraction of essential oil of flowers of tea (Camellia sinensis L.) plants and its antioxidative activity

BACKGROUND To extract natural volatile compounds from tea (Camellia sinensis) flowers without thermal degradation and residue of organic solvents, supercritical fluid extraction (SFE) using carbon dioxide was employed to prepare essential oil of tea flowers in the present study. Four important parameters—pressure, temperature, static extraction time, and dynamic extraction time—were selected as independent variables in the SFE. RESULTS The optimum extraction conditions were the pressure of 30 MPa, temperature of 50°C, static time of 10 min, and dynamic time of 90 min. Based on gas chromatography–mass spectrometry analysis, 59 compounds, including alkanes (45.4%), esters (10.5%), ketones (7.1%), aldehydes (3.7%), terpenes (3.7%), acids (2.1%), alcohols (1.6%), ethers (1.3%) and others (10.3%) were identified in the essential oil of tea flowers. Moreover, the essential oil of tea flowers showed relatively stronger DPPH radical scavenging activity than essential oils of geranium and peppermint, although its antioxidative activity was weaker than those of essential oil of clove, ascorbic acid, tert‐butylhydroquinone, and butylated hydroxyanisole. CONCLUSION Essential oil of tea flowers using SFE contained many types of volatile compounds and showed considerable DPPH scavenging activity. The information will contribute to the future application of tea flowers as raw materials in health‐care food and food flavour industries. © 2013 Society of Chemical Industry