关键词: 山苍子, GC-MS, 提取, 抗氧化活性

Abstract:

【Objective】The objective of this study is to evaluate the effect of three common methods on the DPPH radical scavenging activity and the rate of extraction of Litsea cubeba from the dry fruit. GC-MS analysis was carried out to perform the correlation between chemical composition and antioxidant activity of extracts.【Method】The antioxidant extracts of Litsea cubeba were obtained using liquid-liquid extraction (with ultrasonic assisted or magnetic assisted), SFE (CO₂ super-critical fluid extraction) and steam distillation extraction. The antioxidant activities of the extracts were measured by a free radical scavenging method using 1,1-diphenyl-2-picrylhydrazyl (DPPH). The GC-MS analysis of Litsea cubeba extracts were carried out with added 1,4-dibromobenzene which served as an internal standard. Peak area normalization was used to get the relative amount of main compounds in the respective extracts.【Result】Results demonstrate that the oil has significant antioxidant activity. The natural antioxidants are most effectively extracted by employing liquid–liquid extraction. The ultrasonic assisted liquid-liquid extraction exhibiting the highest oil yields of 26.34%, while magnetic agitation extraction showed highest antioxidant activity of 31.22 mg·mL^-1 (IC₅₀). The antioxidant activity of supercritical carbon dioxide extraction is 56.95 mg·mL^-1. Steam distillation showed lowest antioxidant activity of 64.95 mg·mL^-1. More than 122 compounds were identified by GC-MS analysis, including 12 kinds of fatty acids, 16 kinds of terpenes, 18 kinds of oxygenated terpenes, and other trace compounds including alkenes, alcohols, ketones, and alkanes from these extracts. GC-MS results show that the main components of the oil of Litsea cubeba from dried fruit are saturated fatty acid such as lauric acid, unsaturated fatty acids such as 9-Octadecenoic acid,9,12-Octadecadienoic acid and various terpenes and oxygenated terpenes such as α-pinene, β-pinene, limonene and citral. The fatty acid content of liquid-liquid extraction was 53.51%-66.61%, apparently higher than 17.64% of CO₂ supercritical fluid extraction (SFE) and 8.1% of steam distillation. Meanwhile, the steam distillation and SFE get abundant terpenes and oxygenated terpenes with 29.37% and 17.69%, respectively, which were apparently higher than liquid-liquid extraction with 6.49%-9.75%.【Conclusion】Liquid-liquid extraction with magnetic assisted extraction made a apparently positive affect on the antioxidant activity and the highest compounds of unsaturated fatty acid. Meanwhile, ultra-sonic assisted enhance the yield of oil. The oil extracted by steam distillation rich in terpene compounds and showed lower antioxidant activity (64.95 mg·mL^-1). In addition, HPLC grade citral exhibited the lowest antioxidant activity of IC₅₀ values of 74.33 mg·mL^-1. Thus, we can make a legitimate inference that antioxidant biological activity has been mainly attributed from fatty acid composition (in particular unsaturated fatty acid) rather than terpenes or oxygenated terpenes.

Key words: Litsea cubeba, GC-MS, extraction, antioxidant activity