Mohammad Shoeb

Isolation, Structure Elucidation, and Biological Activity of Flavone 6-C-Glycosides from Alliaria petiolata

Preparative reversed-phase HPLC analysis of a methanol extract of the seeds of Alliaria petiolata afforded fourflavone 6-C-glycosides: isoorientin, swertiajaponin, swertisin and isoscoparin-2″-β-D-glucopyranoside. The molecular structures were elucidated by UV, ESIMS and comprehensive 1D (1H and 13 C) and 2D (gradient multiple quantum filtered 1H-1H COSY, 1H-13C HSQC and 1H-13C HMBC) NMR analyses. The antibacterial and free radical scavenging activity, and general toxicity of these compounds were assessed. While none of these glycosides showed any significant antibacterial activities at test concentrations, all these compounds showed prominent free radical scavenging activity (IC50 values: 1.25×10-2 to 7.69×10-3 mg/mL) in DPPH assay. In the brine shrimp lethality assay very low levels of general toxicity (LD50 >1.00 mg/mL) were displayed.

Eremostachiin: a new furanolabdane diterpene glycoside from Eremostachys glabra

The reversed-phase preparative HPLC analysis of the methanol extract of the rhizomes of Eremostachys glabra (Lamiaceae) led to the isolation of two furanolabdane diterpene glycosides, phlomisoside II, and β-D-glucopyranosyl-(1→2)-β-D-glucopyranosyl ester of phlomisoic acid (named eremostachiin), the latter being a novel natural product. The structure of the new compound has been elucidated unambiguously by HRMS and a series of 1D- and 2D-NMR spectroscopic techniques. The free radical scavenging activity of these compounds was assessed using the DPPH assay.

Swarnalin and cis -swarnalin, two new tetrahydrofuran derivatives with free radical scavenging activity, from the aerial parts of Cuscuta reflexa

The reversed-phase HPLC analysis of a methanol extract of the aerial parts of Cuscuta reflexa afforded a non-separable mixture (55u2009:u200945) of two novel tetrahydrofuran derivatives, named swarnalin (1) and cis-swarnalin (2), and a known coumarin, 5,6,7-trimethoxycoumarin (3). The structures of the compounds were elucidated unequivocally by UV, HRFABMS and a series of 1D and 2D NMR analyses. The mixture of 1 and 2 showed significant free radical scavenging activity in the DPPH assay and the RC50 value was found to be 3.80u2009×u200910−4u2009mgu2009mL−1 for the mixture, compared to 2.88u2009×u200910−5u2009mgu2009mL−1 for the positive control, quercetin.

A mixed crystal of imperatorin and phellopterin, with C-H…O, C-H…π and π-π interactions

The crystal structure of 9-(3-methylxadbut-2-enylxadoxy)xad-7H-furoxad[3,2-g]xadchroxadmen-7-one–4-methoxy-9-(3-methylxadbut-2-enylxadoxy)-7H-xadfuroxad[3,2-g]xadchromen-7-one (0.926/0.074), 0.926C16H14O4·0.074C17H16O5, is characterized by two independent imperatorin molxadecules in the asymmetric unit, which exhibit different side-chain conformations. A small amount of phellopterin overlaps with one of the two imperatorin molxadecules. The supramolxadecular structure is supported by C—H⋯O, C—H⋯π and π–π interactions.