[Extraction technology, composition analysis and antioxidant and antimicrobial activities of volatile oil from fenugreek leaves]

Abstract

To define the extraction process, main components and antioxidative and antimicrobial activities of volatile oil from fenugreek(Trigonella foenum-graecum) leaves and its active substance basis. Response surface methodology was used for optimum supercritical CO_2 extraction conditions of essential oil from fenugreek leaves. The main components of volatile oil were analyzed by GC-MS, its antioxidant activity was evaluated by measuring the scavenging ability of 1,1-diphenyl-2-picrylhydrazyl(DPPH) and 2, 2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid, ABTS) free radical, and the antimicrobial effect of volatile oil was evaluated by K-B paper AGAR diffusion method. The results showed that the optimal extraction temperature was 50 ℃, the extraction time was 89 min, and the extraction pressure was 35 MPa. Under the conditions, the optimum extracting yield of volatile oil was 1.72%,which was about 1.5 times higher than that of the conventional steam distillation. A total of 52 compounds were found based on reference substance retention time and GC-MS fragmentation information or the existing literatures, and the major compounds were oleic acid(9.65%), carveol(9.41%), n-hexadecanoic acid(9.1%), linoleic acid(6.95%), methyl linolenate(5.4%), petroselinic acid(5.3%), testosterone(3.4%), sotolon(1.75%). The volatile oil of fenugreek showed moderate antioxidant activities in DPPH assay(IC_(50) value of 0.473 mg·mL~(-1)) and ABTS test(IC_(50) value of 0.107 mg·mL~(-1)). The oil had a stronger antimicrobial activity in vitro. MIC of the volatile oil ranged from 0.375 to 1.5 mg·mL~(-1). The results showed that the optimized volatile oil extraction process was stable, and the extraction yield was high. Fenugreek leaves contained a variety of volatile components, with obvious antioxidant and antibacterial activities. This study provides a certain theoretical basis for the comprehensive development and utilization of fenugreek.

Keywords: GC-MS; antimicrobial; antioxidant; fenugreek leaves; supercritical CO_2 extraction; volatile oil.