Abstract
A new biflavonoid, 5,7,3',5'',7'',4'''-hexahydroxy (4'-O-3''')-biflavone (1) and a polyketide derivative, methylcylohex-1-ene (3) (previously reported only as a synthetic compound) were isolated from aerial parts of Vangueria infausta. In addition, eight other known flavonoids viz. (-)-epicatechin, epiafzelechin, dihydrokaempferol, quercetin, luteolin (2), dihydroquercetin-3'-O- glucoside, daidzein and genistein were also isolated from this plant. Structures were identified using 1D- and 2D NMR experiments as well as ESI-MS, IR and UV spectra. The new biflavonoid 1 showed higher radical scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) reagent compared to ascorbic acid (standard) using a spectrophotometric method. Compound 1 was less sensitive to Gram-positive and Gram-negative bacterial strains and yeast (Candida mycoderma) compared to luteolin and quercetin on the Bioautographic Agar Overlay Assay.
Highlights
Vangueria infausta Burch is a tree 2-7 meters tall which grows well on semiarid soils and in rain forests, but has a worldwide distribution
The plant material were subjected to chromatographic and gel filtration techniques to give a total of ten compounds with compound 1 being reported for the first time in nature
We report the natural occurrence of 3 as a plant secondary metabolite but had previously been reported only as a synthetic compound[8]
Summary
Vangueria infausta Burch (family Rubiaceae) is a tree 2-7 meters tall which grows well on semiarid soils and in rain forests, but has a worldwide distribution. The plant material (leaves and stem bark extracts) were subjected to chromatographic and gel filtration techniques to give a total of ten compounds with compound 1 being reported for the first time in nature.
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