Ivan Addae-Mensah

Lignans and other constituents from Carissa edulis

Abstract The methanolic extract from the root of Carissa edulis contains ca 5% lignans, the main compounds among them being (−)-nortrachelogenin, carinol and the hitherto unknown carissanol.

Sesquiterpenes from carissa edulis

Abstract The methanolic extract from the root of Carissa edulis contains about 5% sesquiterpenes. Besides carissone, cryptomeridiol and β-eudesmol, three hitherto unknown sesquiterpenes of the eudesmane-type and a novel germacrane derivate have been isolated.

Novel amide alkaloids from the roots of Piper guineense

Abstract Two novel amide alkaloids, wisanine and wisanidine, have been isolated from the petroleum-extract of the roots of Piper guineense , and found to be N -piperidyl-5 (2-methoxy-4,5-methylenedioxyphenyl)- trans -2- trans -4-pentadienamide and N -pyrrolidyl-5-(2-methoxy-4, 5-methylenedioxyphenyl)- trans -2- trans -4-pentadienamide respectively. The structure of wisanidine has been confirmed by synthesis. N -Isobutyl)- trans -2- trans -4-eicosadienamide, recently reported to be present in the fruits of the plant as well as Piperine and Δ α,β -dihydropiperine have also been found to be major constituents of the roots.

Traditional medicines as a mechanism for driving research innovation in Africa

The outcomes from recent high profile deliberations concerning African health research and economic development all point towards the need for a mechanism to support health innovation on the continent. The mission of the African Network for Drugs and Diagnostics Innovation (ANDI), is to promote and sustain African-led health product innovation to address African public health needs through the assembly of research networks, and building of capacity to support human and economic development. ANDI is widely viewed as the vehicle to implementing some of these recommendations. There is tremendous opportunity for Africa, to leverage the expertise in natural products and traditional medicines in support of this objective to kick-start innovation. This report highlights key recommendations that have emerged through expert forums convened by ANDI on the challenges, opportunities and prospects for investing in this important area of research.

Geranial and neral, major constituents of Lippia multiflora Moldenke leaf oil.

ABSTRACT The leaf oils of samples of Lippia multiflora Moldenke collected from different geographic areas of Togo and from cultivated plants were analyzed by GC and GC/MS. Three types of essential oils were characterized, one which is rich in neral and geranial, (23–89%) and two other types, poor in neral and geranial, containing either 1,8-cineole (16–63%) or thymol (15–40%) and p-cymene (15–20%) as the major components. The oils obtained exhibited insecticidal activity against the bruchid Callosobruchus maculatus Fab. in a dose-dependent manner.

N-isobutyl-trans-2-trans-4-eicosadienamide and other alkaloids of fruits of Piper guineense

Abstract A novel alkaloid, N -isobutyl- trans -2- trans -4-eicosadienamide, has been isolated from the fruits of Piper guineense and fully characterized. The structure of the compound has been confirmed by an unambiguous synthesis of the tetrahydro derivative. The known alkaloid, δαβ-dihydropiperine has also been isolated and the position of the double bond in this compound confirmed by the use of an NMR shift reagent.

Isoflavones and coumarins from Milletia thonningii

Abstract From the root wood and the pods of Milletia thonningii six isoflavones and a novel coumarin were isolated. They are alpiniumisoflavone and the 5- O -methyl, O , O -dimethyl, 3′-hydroxy-4′- O -methyl and the 5- O -methyl-4′- O -(3-methyl-2-butenyl) derivatives, together with robustone and the new coumarin, thonningine-C.

The dichapetalins—A new class of triterpenoids☆

Further to our recent report on dichapetalin A, we describe the isolation and structure elucidation by spectroscopic methods of dichapetalins B-H from the roots of Dichapetalum madagascariense. These compounds constitute a novel class of triterpenoids. Dichapetalin A shows a strong and selective cytotoxic activity.

Evaluation of the Quality of Artemisinin-Based Antimalarial Medicines Distributed in Ghana and Togo

This study, conducted as part of our overall goal of regular pharmacovigilance of antimalarial medicines, reports on the quality of 132 artemisinin-based antimalarial medicines distributed in Ghana and Togo. Three methods were employed in the quality evaluation—basic (colorimetric) tests for establishing the identity of the requisite active pharmaceutical ingredients (APIs), semi-quantitative TLC assay for the identification and estimation of API content, and HPLC assay for a more accurate quantification of API content. From the basic tests, only one sample totally lacked API. The HPLC assay, however, showed that 83.7% of the ACTs and 57.9% of the artemisinin-based monotherapies failed to comply with international pharmacopoeia requirements due to insufficient API content. In most of the ACTs, the artemisinin component was usually the insufficient API. Generally, there was a good correlation between the HPLC and SQ-TLC assays. The overall failure rates for both locally manufactured (77.3%) and imported medicines (77.5%) were comparable. Similarly the unregistered medicines recorded a slightly higher overall failure rate (84.7%) than registered medicines (70.8%). Only two instances of possible cross-border exchange of medicines were observed and there was little difference between the medicine quality of collections from border towns and those from inland parts of both countries.

The absolute configuration of dichapetalin A

Abstract The absolute configuration of dichapetalin A, [(4 α ,6′ α ,7 α ,17 α ,20 S ,23 R ,24 E )-2′,3′,5′,6′-tetrahydro-7,23,26-trihydroxy-6′-phenyl-13,30-cyclo-29-nordammara-2,11,24-tri-eno [4,3-c]pyran-21-oic acid γ-lactone], the major cytotoxic constituent from Dichapetalum madagascariense has been established to be 4 R ,5 R ,7 R ,8 R ,9 R ,10 S ,13 R ,14 S ,17 S ,20 S ,23 R ,6′ S .