Comparison of Yield, Chemical Composition and Antimicrobial Activity of Distichochlamys citrea Rhizome Essential Oils Obtained by Different Extraction Methods

Abstract

Hydrodistillation (HD), steam distillation (SD) and microwave-assisted hydrodistillation (MAHD) extraction methods were assessed for their effects on yield, chemical composition and antimicrobial activity of essential oils from Distichochlamys citrea M.F. Newman rhizomes. The greatest essential oil yields (v/w on dry weight basis) were obtained by MAHD (0.37%), followed by HD (0.27%) and SD (0.25%). The extraction time of MAHD was 1 h, compared to 4 h for HD and SD. Gas chromatography and gas chromatography-mass spectrometry were used to analyze the obtained oils. Geranial, neral, α-terpineol, 1,8-cineole, β-pinene and α-pinene were the major components in all oil samples. MAHD resulted in an increase in the content of oxygenated monoterpenes in the essential oil compared to HD or SD. Antimicrobial activity of essential oils was evaluated in terms of minimum inhibitory concentrations (MICs) by the microdilution broth method. All essential oils showed varying degrees of antimicrobial activity, with MICs ranging from 200 to 400 μg/mL. These results indicate that extraction method significantly influences the yield, chemical composition and antimicrobial activity of essential oils from D. citrea rhizomes. Compared with HD and SD methods, MAHD has the advantages of shorter extraction time, increased yield and increased oil quality. Therefore, MAHD is proposed as the preferred method for extracting essential oils from D. citrea rhizomes.