Bioactive proanthocyanidins from the root bark of Cassia abbreviata

Cassia abbreviata is an important medicinal plant used in the treatment of various infectious diseases. The ethnomedical efficacy of extracts of this plant species is attributed to its phytochemical constituents most of which are phenolics and anthraquinones. The aim of this study was to isolate and elucidate bioactive phenolic compounds from the root bark of this species. Consequently, two novel trimmeric proanthocyanidins; 3,7,4'-trihydroxyflavan-(4β→8)-3,5,7,4'-tetrahydroxyflavan-(3'→6)-3,5,7,2',4'- pentahydroxyflavan (cassinidin A) and 3,7,2',4'-tetrahydroxyflavan-(4α→8)-3,5,7,4'-tetrahydroxyflavan-(4α→6)-3,5,7,2',4'-pentahydroxyflavan (cassinidin B) were isolated from the root bark of Cassia abbreviata. The chemical structures were determined using NMR, MS and HRMS spectroscopic data. The cassinidin A and B showed higher to moderate antimicrobial activity against Escherichia coli, Bacillus subtilis, Staphylococcus aureus and Candida mycoderma.Keywords: Medicinal plant, Cassia abbreviata, Caesalpinioideae, root bark, Cassinidin A, Cassinidin B, antimicrobia

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

GC-MS Analysis and Antimicrobial Activities of the Non-polar Extracts of Mundulea sericea

The composition of the non-polar extracts of the leaves, stem bark and twigs of Mundulea sericea (Fabaceae) were analyzed using GC-MS. Eight, five and eleven components were identified from the leaves, twigs and stem bark extract, respectively. The major components were identified as: caryophyllene (43.6 %) and cadina-3,9-diene (29.7 %) in the leaf extract, amorphene (34.4 %) and valencene (17.9 %) in the stem bark extract and isoledene (29.0 %) and α-gurjunene (22.4 %) from the twig extract. Sesquiterpenes were the major abundant components in the non-polar extracts. The leaf, stem bark and twig extracts showed weak antibacterial and antifungal activities.Keywords: Mundulea sericea, GC-MS, non-polar, sesquiterpenes, antimicrobia

Cytotoxic flavonoids from Erythrina caffra Thunb

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 μg/disc (8, 11) and 125 μg/disc (9, 13, 15). KEY WORDS: Erythrina caffra, Cytotoxicity, Antibacterial, Flavonoids, Fabaceae Bull. Chem. Soc. Ethiop. 2016, 30(3), 427-435DOI: http://dx.doi.org/10.4314/bcse.v30i3.1

A comparison of the labour dispute resolution systems of South Africa and Swaziland

History and Background: The history of statutory labour dispute resolution of South Africa dates back to 1909, when the Transvaal Disputes Prevention Act of 1909 was promulgated which applied only to the Transvaal. The Industrial Conciliation Act of 1924 established industrial councils and ad hoc conciliation boards and excluded black workers from the statutory definition of employee and this resulted in a dual industrial relations system that existed up to 1979. The history of statutory labour dispute resolution of Swaziland dates back to 1980 when the first Industrial Relations Act of 1980 was promulgated which established the first Industrial Court. Research Findings: The dispute resolution systems of South Africa and Swaziland contain both similarities and differences. Lessons for Swaziland include combining general and specific dispute resolution procedures, providing the right of a referring party to apply for condonation for late referral of a dispute, using conciliation-arbitration, making arbitration proceedings public hearings, influence of parties on the appointment of arbitrators, court adjudication, pre-dismissal arbitration, court adjudication by judges only, establishment of a constitutional court, full protection of protected strikes/ lockouts from interdicts, legalization of sympathy strikes, and removal of strikes/ lockout ballot. Lessons for South Africa include plural representation of parties at conciliation and arbitration, re-direction of some disputes by the Labour Court to the Commission for arbitration, reporting of labour disputes direct to the Head of State for determination

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

Gypsophila 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 species. 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 (DPPH) 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. Keywords : Gypsophila pilulifera; Free-radical scavenger; Solid-phase extraction; High-performance liquid chromatography (HPLC); Phenylethanoid; Verbascoside

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

The chemistry and biological activity of the Hyacinthaceae

Covering: 1914 to 2012The Hyacinthaceae (sensu APGII), with approximately 900 species in about 70 genera, can be divided into three main subfamilies, the Hyacinthoideae, the Urgineoideae and the Ornithogaloideae, with a small fourth subfamily the Oziroëoideae, restricted to South America. The plants included in this family have long been used in traditional medicine for a wide range of medicinal applications. This, together with some significant toxicity to livestock has led to the chemical composition of many of the species being investigated. The compounds found are, for the most part, subfamily-restricted, with homoisoflavanones and spirocyclic nortriterpenoids characterising the Hyacinthoideae, bufadienolides characterising the Urgineoideae, and cardenolides and steroidal glycosides characterising the Ornithogaloideae. The phytochemical profiles of 38 genera of the Hyacinthaceae will be discussed as well as any biological activity associated with both crude extracts and compounds isolated. The Hyacinthaceae of southern Africa were last reviewed in 2000 (T. S. Pohl, N. R. Crouch and D. A. Mulholland, Curr. Org. Chem., 2000, 4, 1287-1324; ); the current contribution considers the family at a global level