Steven D. Drake

Antimicrobial pterocarpans of nigerian Erythrina mildbraedii

Abstract Bioassay-directed fractionation of ethanolic extracts of the roots of Erythrina mildbraedii , a plant used in the indigenous system of medicine in Nigeria, resulted in the isolation of the previously known pterocarpans erythrabyssin-II and isoneorautenol and the new pterocarpans erybraedins A, B, and C. The structures of the new compounds were determined by chemical transformations and/or spectroscopy and their in vitro antimicrobial spectra and potencies are reported.

Antimicrobial agents from higher plants: Prenylated flavonoids and other phenols from Glycyrrhiza lepidota

Abstract Bioassay directed fractionation of extracts of American licorice, Glycyrrhiza lepidota (Leguminosae), resulted in identification of the known bibenzyl, 3,5-dihydroxy-4-(3-methyl-2-butenyl)-bibenzyl, and the known flavanones, glabranin and pinocembrin, as well as the isolation and structure determination of the new flavonol, glepidotin A and the new dihydroflavonol, glepidotin B as antimicrobial agents.

Erycristin, a new antimicrobial petrocarpan from Erythrina crista-galli

Abstract Bioassay-directed fractionation of ethanolic extracts of the stern bark of Erythrina crista-galli resulted in the isolation of a new pterocarpan, erycristin, and two previously known pterocarpans, sandwicensin and erythrabyssin-II. The structure of erycristin was determined by spectroscopic examination and by chemical transformation of sandwicensin. The absolute stereochemistry of erycristin was established by circular dichroism measurements. Erythrabyssin-II diacetate was converted to erycristagallin diacetate, supporting the previous proposed structure of erycristagallin.

Isolation and Identification of Higher Plant Agents Active in Antimutagenic Assay Systems: Glycyrrhiza Glabra

The reproduction and maintenance of identity of species are biological imperatives, and it is not surprising that there exist mechanisms to minimize or repair the deleterious influence of noxious chemicals in the environment on DNA. Animals tend to defend themselves through the use of enzymes which intercept aggressive chemicals and convert them to less dangerous substances. Animal cells also contain a variety of preformed smaller molecular weight chemicals which can react with oxidized species and free radicals and convert them to less virulent electrophiles (1). It is now becoming clear that higher plants also contain a variety of preformed secondary metabolites which represent a structurally diverse array of antimutagenic and desmutagenic compounds (6). Many, but not all, would appear to be enzyme inhibitors or antioxidants. Since a number of plant constitu-ents are mutagenic (18), it seems reasonable that higher plants should also contain molecules capable of antimutagenicity so as to survive the effects of their own metabolism. Study of such substances has the potential of revealing much interesting molecular detail about the processes of mutagenesis and antimutagenesis. A rather more distant hope is that such substances might be safe enough to provide protection for individuals perceived to be at risk. This would appear to be the case with a number of minor anticarcinogenic constituents consumed as part of our diet (4, 20).

Antimicrobial alkaloids from Boehmeria cylindrica

Abstract Investigation of extracts of Boehmeria cylindrica resulted in identification of cryptopleurine and 3,4-dimethoxy-ω-(2′-piperidyl)acetophenone, known alkaloids, as agents responsible for intense activity against Candida albicans . Julandine, the secophenanthroquinolizidine alkaloid related to cryptopleurine, was also active but not definitely identified in the extracts examined.

Amorphastilbol, an antimicrobial agent from Amorpha nana

Abstract Bioassay-directed fractionation of Amorpha nana demonstrated that the anti Gram positive/antitubercular constituent is amorphastilbol. The chemical structure of amorphastilbol was confirmed by chemical transformation to known ( Radula variabilis ) dihydroamorphastilbol and its methyl ether. Inactive 3,5-dihydroxy-7,4′-dimethoxyflavone was detected in this plant for the first time and identified by interconversion with kaempferol. All compounds were evaluated in vitro for antimicrobial spectrum and potency.

Antimicrobial agents from higher plants: two dimethylbenzisochromans from Karwinskia humboldtiana

Abstract Two new antimicrobial dimethylbenzisochromans were isolated from the roots of Karwinskia humboldtiana together with the known 7-acetyl-6,8-dimethoxy-3-methyl-l-naphthol. The structures and absolute configurations were determined by spectroscopic examination and by chemical transformation to the known quinones eleutherin and 7-methoxyeleutherin.

Antimicrobial agents from higher plants: Activity and structural revision of flemiflavanone-D from Flemingia stricta

Abstract Flemiflavanone-D from Flemingia stricta is active in vitro against Staphylococcus aureus and Mycobacterium smegmatis . Reexamination and interpretation of its spectral properties required revision of its molecular formula to C 25 H 28 O 6 and its structure to 2 S -5,7,4′-trihydroxy-6-γ,γ-dimethylallyl-3′-γ,γ-dimethylallyl-oxidoflavan-4-one. The new structure was confirmed when reaction with chlorotrimethylsilane sodium iodide in acetonitrile deoxygenated and cyclized flemiflavanone-D to the known dicycloeuchrestaflavanone A. The absolute stereochemistry of flemiflavanone-D was established to be 2 S by circular dichroism measurements.