Glucosinolates, glycosidically bound volatiles and antimicrobial activity of Aurinia sinuata (Brassicaceae)

Abstract

Volatiles of Aurinia sinuata (L.) Griseb. were isolated from aerial parts and analysed by gas chromatography/gas chromatography–mass spectrometry (GC/GC–MS). The main compounds were glucosinolate degradation products originating from glucoberteroin, glucobrassicanapin and glucoalyssin. They were: 6-(methylthio)hexanenitrile (1.8–51.5%), 6-(methylsulfinyl)hexanenitrile (0–11.5%), 5-(methylsulfinyl)pentyl isothiocyanate (0–10.2%), 5-(methylthio)pentyl isothiocyanate (0.4–9.5%), 4-pentenyl isothiocyanate (0.7–8.9%), 5-hexenenitrile (2.6–14.6%) and 5,6-epithiohexanenitrile (0–3.4%). Also other volatiles were identified, such as fatty acids and esters (0.3–19.2%), phenols, phenylpropane derivatives and related compounds (0.4–15.8%), aliphatic alcohols and carbonyl compounds (4.2–11.6%) and some other compounds in smaller percentages. The O-glycosidically bound volatiles were isolated from aerial parts of A. sinuata. After the enzymatic hydrolysis and GC and GC–MS analyses, among 20 volatile aglycones identified, eugenol (73.0%) was the main one. The volatile samples containing glucosinolate degradation products were evaluated for antimicrobial activity using the disc diffusion method with calculated minimum inhibitory concentrations (MIC). All volatile samples expressed a wide range of growth inhibition activity against both Gram-positive and Gram-negative bacteria and fungi. The minimum inhibitory concentrations varied between 0.008 and 0.115 mg/ml.