PUB - Publikationen an der Universität Bielefeld

The work we carried out for the account of this thesis concerned the chemical investigation of three plants used in Cameroonian traditional medicine, Maesopsis eminii (Rhamnaceae), Autranella congolensis (Sapotaceae) and Pentadesma grandifolia (Guttiferae). 13 compounds were isolated from the bark of Maesopsis eminii (Engl.). Two pentacyclic triterpenes, 1[alpha],3[beta]-dihydroxybauer-7-en-28-oic acid (85) and 3[beta]-dihydroxybauer-7-en-28-oic acid (86) of which (85) is reported here for the first time, together with four steroids labelled 91, 92, 24 and 25, and seven phenolic compounds 87-90, 93, 9, 97+98, were isolated from this plant. Compound 93 was derivatized to its acetate derivative labelled 94. Triterpenes were isolated for the first time from this plant and the new compound 85 displays moderate antibacterial activity against Gram-positive bacteria such as Bacillus subtilis ATCC while compound 88 displays good anti-inflammatory activity (IC50 9.5 µM) by inhibiting highly the 3[alpha]-hydroxysteroid dehydrogenase. The X-ray diffraction analysis of the crystal of the new triterpene was also obtained. Six known compounds have been isolated from the bark of the plant Autranella congolensis (De Wild.) A. Chev., taraxerol (99), taraxerone (100), a mixture of 3[beta]-docosanoyltaraxer-14-ene (n = 20), 3[beta]-tetracosanoyltaraxer-14-ene (n = 22), 3[beta]-hexacosanoyltaraxer-14-ene (n = 24) (101), (+)-catechin (97), (24R)-stigmast-7,22(E)-dien-3[alpha]-ol (26) and 24-feruloyltetracosanoic acid (102). Six known compounds have also been isolated from the root bark of Pentadesma grandifolia (E. G. Baker), a bicyclic triterpenoid (13E,17E)-polypoda-7,13,17,21-tetraen-3[beta]-ol (105), lupeol (23) and four xanthones [alpha]-mangostin (103), rubraxanthone (104), garcinone E (106) and cowanin (108). Compounds 104 and 105 displayed good anti-inflammatory activity when tested against 3[alpha]-hydroxysteroid dehydrogenase. In addition, 104 selectively inhibits the cyclooxygenase-2 (COX-2). Methods used for the isolation of compounds were mainly column chromatography, preparative TLC, and HPLC using solvents with differents polarities and selectivity. The structures of all compounds were elucidated by using modern spectroscopic techniques such as 1D and 2D-NMR (HH-COSY, HMBC, HMQC), HRMS and IR spectroscopy.