Chemical composition and antioxidant and antimicrobial activities of essential oil of Allium sphaerocephalon L. subsp sphaerocephalon (Liliaceae) inflorescences

BACKGROUND: Allium sphaerocephalon is a wild-growing plant commonly used as an onion substitute. In this study the essential oil obtained from A. sphaerocephalon subsp. sphaerocephalon inflorescences was analysed by gas chromatography and gas chromatography/mass spectrometry and also evaluated for in vitro antioxidant and antimicrobial activities. The obtained results are reported for the first time and discussed with respect to the sulfur compounds detected in the essential oil. RESULTS: Ninty-one compounds were identified, representing 91.6% (w/w) of the total oil. Major constituents of the analysed sample were shyobunol (15.3%), beta-caryophyllene (8.1%), alpha-cadinol (7.8%), 3,5-diethyl-1,2,4-trithiolane (isomer II, 5.9%) and delta-cadinene (5.2%). The diluted oil had an antioxidant capacity of 160 000 +/- 111 mu mol alpha-tocopherol acetate equivalents g(-1). Its antimicrobial activity was evaluated against five bacterial and two fungal strains using the broth microdilution assay. Among the micro-organisms tested, the most susceptible strains were Pseudomonas aeruginosa (minimal inhibitory/bactericidal concentration = 0.08/2.5 mg mL(-1)) and Aspergillus niger (minimal inhibitory/fungicidal concentration = 0.31/0.63 mg mL(-1)). CONCLUSION: The results showed that the examined species had strong antioxidant and antimicrobial properties and are in accordance with the popular use of plants belonging to the genus Allium in traditional medicine, emphasising the necessity of further detailed study of the active principles in Allium species. (C) 2010 Society of Chemical Industry