Laser trilobum essential oils: composition, antimicrobial and antiradical properties

Abstract

We have investigated the essential oils of Laser trilobum Hayek (Umbelliferae), isolated by hydrodistillation from air-dried rhizome (sample 1) and mature fruits (sample 2) [1]. Essential oil yields were 0.51% and 6.9% (w/w), respectively. The composition of oils, determined using GC-FID and GC-MS, was significantly different. In dark-blue rhizome oil, forty-six compounds (93.1% of the total oil) were identified (71.5% were monoterpenes and 15.3% were sesquiterpenes). The major components were α-pinene (31.5%), γ-terpinene (9.0%), p-cymene (7.9%) and 1,4-dimethyl azulene (6.0%). In colorless fruits oil nineteen monoterpenes (96.8% of the total oil) were identified. The main constituents were limonene (51.6%) and perilla aldehyde (26.8%). Antimicrobial activity of oils was tested using the agar diffusion [2] and broth microdilution methods [3] against Staphylococcus epidermidis ATCC 12228, S. aureus ATCC 25923, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Klebsiella pneumoniae NCIMB 9111, Enterococcus faecalis ATCC 29212 and Candida albicans (ATCC 10259 and 24433). Rhizome oil was also tested against Micrococcus flavus ATCC 10240 and fruits oil against M. luteus ATCC 9341 and Bacillus subtilis ATCC 6633. The best activity exhibited rhizome oil against E. coli, K. pneumoniae and C. albicans (MIC 25µg/ml, MBC 50µg/ml), and fruits oil against C. albicans ATCC 10259 (MIC 12.5µg/ml, MBC 50µg/ml). DPPH-radical scavenging ability of fruit oil, determined spectrophotometrically [4], was concentration-dependent and with SC50=160µl/ml. Rhizome oil was preliminary tested using TLC-DPPH assay [4], revealing the dark-blue spot on the front of oil chromatogram as the main anti-DPPH scavenger.