Glucosinolate degradation products and other bound and free volatiles in the leaves and roots of radish (Raphanus sativus L.)

The volatile constituents from the leaves and roots of Raphanus sativus var. black, white and red were isolated by hydrodistillation in a Clevenger-type apparatus and were analysed by gas chromatography and gas chromatography–mass spectrometry. The major components found in the oil of all leaves were phytol (65.3–69.7%), hexadecanoic acid (2.5–14.3%), methyl linolenate (2.1–11.1%) and (Z)-3-hexen-1-ol (0.7–6.9%). Corresponding aliphatic or aromatic glucosinolate compounds identified in the leaves constituted only 0.3–5.7% of the isolated volatiles. They were 5-(methylthio)-4-pentenenitrile (0.3–2.2%), 4-(methylthio)butyl isothiocyanate (0.3–1.7%), 2-phenylethyl isothiocyanate (0.4%), 4-(methylthio)-3-butenyl isothiocyanate, 4-methylpentyl isothiocyanate, benzyl isothiocyanate and benzenepropanenitrile. The major components in the oil of all roots were hexadecanoic acid (30.3–49.9%), 4-(methylthio)butyl isothiocyanate (17.9–25.7%), methyl linolenate (8.5–21.7%), 5-(methylthio)-4-pentenenitrile (1.5–6.9%), dimethyl trisulfide (1.1–3.8%), 5-(methylthio)pentyl isothiocyanate (0.5–2.0%), 4-(methylthio)-3-butenyl isothiocyanate (0.2–1.8%) and 2-phenylethyl isothiocyanate (0.1–1.5%).O-Glycosidically-bound volatiles were isolated and hydrolysed by β-glucosidase from almonds. Nineteen volatile aglycones were identified for the first time in the leaves of all varieties of radish. The main aglycones were eugenol (29.2–37.1%), 2-phenylethanol (2.0–23.5%), 4-vinyl-2-methoxyphenol (2.4–12.4%), (Z)-3-hexen-1-ol (2.6–10.4%), methyl vanillate (6.3–10.0%), 1H-indole (0.7–6.8%), benzyl alcohol (1.4–4.2%), vanillin (3.5–6.3%) and methyl salicylate (0.8–3.4%). However, no volatile aglycones were detected after isolation in different varieties of radish root.