Maureen Byres

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.

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 (55 : 45) 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 3.80 × 10−4 mg mL−1 for the mixture, compared to 2.88 × 10−5 mg mL−1 for the positive control, quercetin.

Supramolecular structures of six adenine-carboxylic acid complexes

Studies concentrating on hydrogen bonding between the bases of DNA and small molecule proton acceptor/donators have led to an increased understanding of the role such complexes have in DNA binding. Here anhydrous and solvated multicomponent crystals of adenine have been prepared with benzoic acid, adipic acid, salicylic acid, 2,6-dihydroxybenzoic acid and 3,5-dihydroxybenzoic acid. The six crystalline forms reported are an anhydrous cocrystal, a methanolated cocrystal, an anhydrous proton-transfer complex, a hydrated proton-transfer complex, a methanolated proton-transfer complex and a doubly hydrated salt. All products were formed in solution and obtained by the slow evaporation technique. A comparison of hydrogen bonding motifs in the products is presented.

The Assessment of Biological Activities Associated with the Major Constituents of the Methanol Extract of ‘Wild Carrot’ (Daucus carotaL.) Seeds

Daucus carotaL. (Family: Apiaceae alt.Umbelliferae), commonly known as ‘wild carrot’ or ‘Queen Anne’s-lace,’ is an ecologically invasive erect biennial naturalized to Scotland. The ethno-botanical uses of this species include applications in the treatment of cough, diarrhea, dysentery, cancer, malaria and tumors, and as an antiseptic, abortifacient, aphrodisiac, carminative, stimulant, stomachic and tonic. The major constituents isolated from the methanol extract of D. carotaseeds by reversed-phase preparative high performance chroma-tography were luteolin, luteolin 3′-O-β-D-glucopyranoside and luteolin 4′-O-β-D-glucopyranoside, three flavones. The constituents were assessed for their antibacterial and free radical scavenging activities, as well as toxicity towards brine shrimp. Among these three flavones, lu-teolin showed the highest degree of free radical scavenging activity (RC50 = 4.3 ×10−4 mg/mL) in the 2,2-diphenyl-l-picrylhydrazyl (DPPH) assay. Both luteolin and its 4′-0-glucoside demonstrated bactericidal activity against Staphylococcus aureusand Escherichia coli(Minimum Inhibitory Concentration [MIC] = 5.0 ×10−2-1.0 ×10−1 mg/mL). Luteolin also demonstrated antibactericidal activity against Bacillus cereusand Citrobacter freundii(MIC = 5.0 ×10−2 mg/mL). Luteolin 3′-0-glucoside showed bactericidal activity against Bacillus cereusand Lactobacillus plantarum(MIC = 2.5 ×10−1 mg/mL and 5 ×10−1 mg/ mL, respectively). In the brine shrimp lethality assay, the LD50 value of luteolin was 5.3 ×10−2 mg/mL, and that of its 3′-0-glucoside and 4′-0-glucoside were > 1.0 mg/mL.

The supramolecular structure of 6-hydroxy-1,3-benzoxathiol-2-one (tioxolone).

The planar molecules of 6-hydroxy-1,3-benzoxathiol-2-one, C(7)H(4)O(3)S, are linked by extensive O-H.O and C-H.O hydrogen bonding and are further stablilized by face-to-face pi-pi interactions.