Chemical composition and antimicrobial activity of volatiles from Degenia velebitica, a European stenoendemic plant of the Brassicaceae family.

Free and glucosidic bound leaf volatiles of Degenia velebitica were isolated and fractionated simultaneously into H(2)O-soluble, H(2)O-insoluble, and highly volatile compounds by hydrodistillation-adsorption (HDA) and analyzed by GC/MS. Among the 24 constituents identified, the main compounds obtained by the HDA method were S- and/or N-atom containing compounds, i.e., 6-(methylsulfanyl)hexanenitrile (10; 26.78%), dimethyl trisulfide (6; 26.35%), 3,4,5-trimethylpyrazole (17; 13.33%), hex-5-enenitrile (2; 10.11%), dimethyl tetrasulfide (8; 4.93%), and pent-4-enyl isothiocyanate (7; 4.45%). In addition, O-glycosidically bound volatiles and free volatiles were isolated by solvent extraction. Sixteen volatile O-aglycones and twelve free volatile components were identified. The main O-aglycones were eugenol (19; 24.15%), 2-methoxy-4-vinylphenol (11; 11.50%), and benzyl alcohol (20; 9.49%), and the main free volatiles were (9Z,12Z)-octa-9,12-dienic acid (38.35%), hexadecanoic acid (22.64%), and phytol (5.80%). The H(2)O-soluble volatile fraction obtained by HDA, containing mostly glucosinolate degradation products and 3,4,5-trimethylpyrazole (17), was evaluated for antimicrobial activity by determining inhibition zones with the diffusion method as well as minimal inhibitory concentrations (MIC) and minimal microbicidal concentrations (MMC) with the micro-dilution method. The fraction expressed activity against the tested Gram-positive and Gram-negative bacteria as well as against yeast, with MIC values equal to or lower than 16.7 μg/ml.