Synthesis and antibacterial activities of cyclodimers of styrene oxides

A simple synthetic procedure for preparation of 1,4-dioxanes or 1,3-dioxolanes from styrene oxides is described. Electron-donating groups on the aromatic ring of the styrene oxides were found to favour formation of 1,4-dioxanes while electron-withdrawing groups favoured formation of 1,3-dioxolanes. Antibacterial activities of the prepared cyclodimers are reported. KEY WORDS: Dioxanes, Dioxolanes, Styrene, Epoxidation, Cyclodimerization, Antibacterial activities Bull. Chem. Soc. Ethiop. 2011, 25(2), 299-304

FACILE ENANTIOSELECTIVE PALLADIUM CATALYSED TRANSFER HYDROGENATION OF α-METHYLCINNAMIC ACID IN THE PRESENCE OF OPTICAL PURE ORGANIC ACIDS

An efficient and enantioselective method for catalytic transfer hydrogenation of the C=C double bond of α-methylcinnamic acid with the aid of chiral organic acids as the hydrogen donors and palladium(II) chloride as the catalyst is reported. Enantiomeric excess was assayed using optical rotation measurements. The best stereoselectivity was achieved when L-(+)-tartaric acid was used as the hydrogen donor and acetonitrile as the solvent. KEYWORDS: Enantioselective, Chiral, α-Methylcinnamic acid, Transfer hydrogenation, Palladium(II) chloride Bull. Chem. Soc. Ethiop. 2007, 21(3), 457-460

GC-MS Analysis and Preliminary Antimicrobial Activity of Albizia adianthifolia (Schumach) and Pterocarpus angolensis (DC)

The non-polar components of two leguminoceae species Albizia adianthifolia (Schumach), and Pterocarpus angolensis (DC) were investigated. GC-MS analysis of the crude n-hexane and chloroform extracts together with several chromatographic separation techniques led to the identification and characterization (using NMR) of sixteen known compounds from the heartwood and stem bark of Albizia adianthifolia and Pterocarpus angolensis respectively. These constituents include, n-hexadecanoic acid (palmitic acid) 1, oleic acid 2, chondrillasterol 3, stigmasterol 4, 24S 5α-stigmast-7-en-3β-ol 5, 9,12-octadecadienoic acid (Z,Z)-, methyl ester 6, trans-13-octadecanoic acid, methyl ester 7, tetradecanoic acid 8, hexadecanoic acid, methyl ester 9, octadecanoic acid 10, tetratriacontane 11, 7-dehydrodiosgenin 12, lupeol 13, stigmasta-3,5-diene-7-one 14, friedelan-3-one (friedelin) 15, and 1-octacosanol 16. Using agar over lay method, the preliminary antimicrobial assay for the extracts was carried out against bacterial (E. coli, P. aeruginosa, B. subtilis, S. aueus) and a fungus/yeast (C. albicans) strains. The n-hexane and chloroform extracts of A. adianthifolia showed the best activity against E. coli with minimum inhibition quantity (MIQ) of 1 µg each while the remaining exhibited moderate-to-weak activity against the test microorganisms

New flavonoids from the stem bark of Erythrina caffra Thunb.

Desta ZY, Sewald N, Majinda RRT. New flavonoids from the stem bark of Erythrina caffra Thunb. Natural Product Research. 2014;28(9):667-673.Three new flavonoids 5,7-dihydroxy-2 ',4 '-dimethoxy-5 '-formylisoflavanone (erycaffra E) (1), 5,7-dihydroxy-3 '-(2 ''-hydroxy-3 ''-methylbut-3-enyl)-5 '-(3"'-hydroxy-3"'-methyl-trans-but-1-enyl)-4 '-methoxyflavanone (erycaffra D) (2) and 5,7-dihydroxy-4 '-methoxy-3 ',5 '-di-(3 ''-hydroxy-3 ''-methyl-trans-but-1-enyl)flavanone (erycaffra F) (3) were isolated from the stem bark of Erythrina caffra along with four known compounds, namely 5,4 '-dihydroxy-6-(3 ''-methylbut-2 ''-enyl)-5"'-hydroxyisopropyldihydrofurano[2"',3"':7,8]isoflavone (isosenegalensein) (4), 5,7-dihydroxy-4 '-methoxy-3 '-(3 ''-methylbut-2-enyl)-5 '-(3"'-hydroxy-3"'-methylbut-1-enyl)flavanone (burttinone) (5), 5,4 '-dihydroxy-5 ''-hydroxyisopropyldihydrofurano[2"',3"':7,6]isoflavone (erythrinin C) (6) and 5,4 '-dihydroxy-6 ''-hydroxymethyl-6 ''-methylpyrano[2 '',3 '':6,7]isoflavone (erysubin B) (7). The structures were determined on the basis of spectroscopic data (1D, 2D NMR and MS) and by comparison with literature values

CYTOTOXIC FLAVONOIDS FROM ERYTHRINA CAFFRA THUNB

Desta ZY, Sewald N, Majinda RRT. CYTOTOXIC FLAVONOIDS FROM ERYTHRINA CAFFRA THUNB. BULLETIN OF THE CHEMICAL SOCIETY OF ETHIOPIA. 2016;30(3):427-435.Erythrina caffra is an important medicinal plant native to South Africa. Its stem bark was investigated for the flavonoid constituents and biological activity. Some isolated flavonoids, 3, 5, 6, 8, 9, 10, 11, 12, 13, 15 and 16 were found to be active against the human cervix carcinoma KB-3-1 cells with IC50 values in the micromolar range. Compounds 8, 9, 11, 13 and 15 also showed weak to moderate antibacterial activity against some organisms using the disc diffusion assay at loadings of 62.5 mu g/disc (8, 11) and 125 mu g/disc (9, 13, 15)

Fast and efficient synthesis of flavanones from cinnamic acids

<p>A fast and efficient synthesis of flavanones from cinnamic acids in three steps has been developed. First, the cinnamic acid was converted to cinnamyol chlorides using SOCl₂. The acid chlorides were then treated with substituted phenols in BF₃ · OEt₂ to furnish corresponding chalcones in 42(75% yields. Base-catalyzed cyclization of the chalcones at room temperature afforded corresponding flavones in 85–95% yields. The conversion of the cinnamic acid derivatives to corresponding chalcones was found to be sensitive to the position and nature of the substituents on the aromatic rings.</p

Assessment of free-radical scavenging activity of Gypsophila pilulifera: assay-guided isolation of verbascoside as the main active component

WOS: 000336187800005Gypsophila pilulifera, Boiss & Heldr, Caryophyllaceae, is a perennial medicinal herb that grows in the-southwestern region of Turkey. Except for only one report on the isolation-of cytotoxic. saponins from the underground parts of G. pilulifera, there are no published thorough phytochemical or bioactivity studies on this specie. In the present study; the free-radical Scavenging activity of extracts and fractions of the-stems of G. pilulifera was evaluated, using a. slightly modified and more-precise-version of the 2,2-diphenyl-1-picrylhydrazyl (DRPH) assay, :reported here for the first time. The DPPH assay-guided HPLC-PDA-purification of the active solid-phase extraction fraction (50% methanol in water) of the methanolic-extract exhibited verbascoside as the main free-radical Scavenger present in this species. The structure of this active compound was resolved by spectroscopy, and the free-radical scavenging potential of verbascoside was determined. (C) 2014 Sociedade Brasileira. de Farmacognosia. Published by Elsevier Editora Ltda. All rights reserved.

New isoflavan from <i>Erythrina livingstoniana</i>

Chemical investigation of the root wood of Erythrina livingstoniana led to the isolation of one previously undescribed isoflavan (3S,3″R)-7-hydroxy-2′-methoxy-[3″-hydroxy-2″,2″-dimethylpyrano (3′,4′)] isoflavan 1, together with eleven known compounds 2-12. The structure of compound 1 was elucidated on the basis of extensive spectroscopic and spectrometric analyses (1 D and 2 D-NMR and APCI-HRMS), with absolute configurations established by comparison of experimental and DFT calculated ECD data. The assignment of the absolute configurations of C-3 and C-3″ of compounds 2 and 3, respectively, were reported for the first time. Compounds 1 − 4 were evaluated for their antibacterial activities in vitro against E. coli ATCC 25922 and S. aureus ATCC 25923. Compound 1 exhibited moderate antibacterial activity with MIC value of 0.063 mg/mL against the clinically relevant risk-group 2 (RG-2) bacterium S. aureus.</p