ZHAO Dandan, PAN Linju, YANG Shiyu, GAO Xinyang, ZHANG Qingfen, LU Qi, CHEN Chunxia
The extraction, chemical composition, and antibacterial activity of volatile oil of wild fresh Allium macrostemon Bunge in northeast China were studied by enzymatic pretreatment combined with a solvent-free microwave method.GC-MS was used to analyze the chemical components of volatile oils extracted by hydrodistillation (HD), solvent-free microwave extraction (SFME), and enzymatic pretreatment combined with solvent-free microwave extraction (EP-SFME).The inhibitory effect of volatile oil on five bacteria (Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Staphylococcus aureus, and Listeria monocytogenes) was determined by diffusion method and twofold dilution method of filter paper agar plate, and finally, the inhibition mechanism of E.coli was explored.The results showed that the essential oil yield extracted by the EP-SFME [(0.115±0.025)%] was 76.92% and 21.10% higher than that by the HD and SFME.GC-MS analysis showed that the main compound contents in the essential oil extracted by the EP-SFME were significantly increased, and the main compounds with an increase of more than 2%, including oxalic acid-4-chlorophenyl nonyl ester (+19.53%), allyl dithioacetate (+19.48%), 1-hexadecyne (+11.86%), 3, 4-dimethylthiophene (+8.02%), 3, 4-dimethylthiophene-2-thiol (+5.94%), phthalic acid-cyclobutyl tridecyl ester (+3.34%), 1, 2, 4-benzenetricarboxylic acid-1, 2-dimethyl ester (+3.07%), 1, 3-dioxane-2, 2, 4, 6-tetramethyl-, trans-1, 3-dioxane-2, 2, 4, 6-tetramethyl (+2.84%) and 2-mercapto-3, 4-dimethyl-2, 3-dihydrothiophene (+2.04%), etc.Among them, sulfur-containing and oxygen-containing compounds were the main components.The antibacterial activity of the volatile oil obtained by the EP-SFME against the five bacteria was stronger than that of the HD and SFME.Among them, the growth inhibition effect on E.coli was the strongest, with the minimum inhibitory concentration and minimum bactericidal concentration of 3.13 mg/mL and 6.25 mg/mL, respectively.Volatile oils inhibited the growth of E.coli mainly by destroying the cell membrane and cell wall of E.coli, inducing protein and nucleic acid leakage.The EP-SFME could effectively extract high-quality essential oil with high antibacterial activity from northeast wild fresh Allium macrostemon Bunge.