Salfredin B11

Although the medicinal plant and food Nigella glandulifera Freyn has been researched for decades, isobenzofuranones have never been isolated before. Two isobenzofuranone derivatives and two saponins were successfully separated and purified from seeds of N. glandulifera Freyn by high-speed counter-current chromatography (HSCCC) with the optimized two-phase solvent system, n-hexane-ethyl acetate-methanol-water (7:3:5:5, v/v). Salfredin B(11) (22.1mg, HPLC purity 95.3%), 5, 7-dihydroxy-6-(3-methybut-2-enyl) isobenzofuran-1(3H)-one (18.9mg, HPLC purity 97.3%) and crude sample 2 (555mg) were separated from 600mg of ethyl acetate extract of N. glandulifera Freyn. Following a cleaning-up step by chromatography on Sephadex LH-20, hederagenin (12mg) and 3-O-[beta-d-xylopyranosyl-(1-->3)-alpha-l-rhamnopyranosyl-(1-->2)-alpha-l-arabinopyranosyl]-hederagenin (45mg) were separated from sample 2. All of the fractions before peak II were collected and subjected to a Sephadex LH-20 column and eluted by methanol, two of triterpene saponins (12mg of hederagenin and 45mg of 3-O-[beta-d-xylopyranosyl-(1-->3)-alpha-l-rhamnopyranosyl-(1-->2)-alpha-l-arabinopyranosyl]-hederagenin) were isolated. The structures of peak fractions were identified by IR, electron ionization MS, (1)H NMR and (13)C NMR. 5, 7-Dihydroxy-6-(3-methybut-2-enyl) isobenzofuran-1(3H)-one was isolated for the first time from higher plant and salfredin B11 was isolated for the first time in this plant.

A new fatty acid ester (1) and seven known phenolic compounds, i.e. salfredin B11 (2), nigephenol C (3), nigephenol B (4), acetovanillion (5), p-hydroxybenzoic acid (6), p-hydroxy-acetophenone (7) and p-hydroxybenzaldehyde (8), were isolated from the seeds of Nigella sativa var. hispidula. Among them, compounds 5, 7 and 8 were isolated from Nigella for the first time. Their structures were elucidated with HR-ESI-MS, 1D and 2D NMR spectra. Evaluation of the isolated compounds on protein tyrosine phosphatase (PTP1B) assay indicated that although compounds 2-8 show no promising anti-PTP1B activities, compound 1 possess anti-PTP1B activity with an IC50 value of 7.38 ± 0.14 μM in vitro.