Isolation and structural elucidation of 4-(β-D-glucopyranosyldisulfanyl)butyl glucosinolate from leaves of rocket salad (Eruca sativa L.) and its antioxidative activity

A structurally unique glucosinolate (GSL) was identified to be 4-(beta-(D)-glucopyranosyldisulfanyl)butyl GSL in rocket leaves. The positive-ion electrospray ionization mass spectrometry (ESI-MS) data indicated that the new GSL had a molecular weight of 521 (m/z 522, [M + H](+), as desulfo-GSL). The molecular formula of the substance was determined to be C17H32O11NS3 (m/z 522.1143, [M + H](+)) based on its positive-ion high-resolution fast atom bombardment mass spectrometry (HR-FAB-MS) data. For the further confirmation, desulfated GSL of 4-(beta-(D)-glucopyranosyldisulfanyl)butyl GSL was prepared by commercial 1-thio-beta-(D)-glucose and dimeric 4-mercaptobutyl desulfo-GSL, which was also isolated from rocket leaves, and its chemical structure was then confirmed by MS data and nuclear magnetic resonance (NMR) spectroscopy. In addition, the antioxidative activity of 4-(beta-(D)-glucopyranosyldisulfanyl)butyl desulfo-GSL was measured by means of chemiluminescence (CL) for evaluating the functional properties. The antioxidative activity (2.089 unit/g) was relatively higher than that of dimeric 4-mercaptobutyl desulfo-GSL (1.227).