Bioactive constituents from Trichilia dregeana Sond. (Meliaceae).

The chemical investigation of the methanolic leaf extract of Trichilia dregeana Sond. led to the isolation of a hitherto unreported cycloartane-type triterpene, dregeanol (1), together with nine known compounds, (3ß,23E)-9,19-cyclolanosta-23,25-dien-3-ol (2), 9,19-cyclolanost-24-en-23-one (3), 6ß-hydroxystigmasta-4,22-dien-3-one (4), lyoniresinol (5), maslinic acid (6), asperphernamate (7), mixture of stigmasterol (8) and ß-sitosterol (9) and ß-sitosterol-3-O-ß-D-glucopyranoside (10). The structures of the isolates were elucidated by extensive spectroscopic and spectrometric analyses (1D and 2D NMR, ESI-MS) and by comparison with previously reported data. Compounds 2 and 6 showed significant antibacterial effect against Escherichia coli and Salmonella enteritidis, res-pectively, with MIC value of 31.25 µg/mL, whilst they displayed moderate antifungal effect with MIC value of 62.5 µg/mL against Candida albicans. All the isolates except compound 3 were found to possess a weak antioxidant potential in the DPPH, ABTS and FRAP assays.

Bioactive constituents from Flacourtia vogelii Hook.f. (Flacourtiaceae).

The chemical investigation of the methanolic root extract of Flacourtia vogelii led to the isolation of a new arylbenzoate derivative, vogelinal (1), together with thirteen known compounds (2-14). The structures of the isolates were elucidated by extensive spectroscopic and spectrometric analyses (1D and 2D NMR, ESI-MS) and by comparison with previously reported data. All the compounds were tested for their antioxidant, antifungal and antibacterial activities. Compound 7 exhibited the highest antioxidant potential, with RSa50of 11.80 ± 2.13 µg/mL, RSa50of 42.60 ± 6.32 µg/mL and RC50 of 51.60 ± 7.71 µg/mL for the DPPH, ABTS and FRAP assay, respectively. Compound 13 displayed weak antifungal effect with MIC value of 125 µg/mL against Candida parapsilosis. Compound 8 showed weak antibacterial effect with MIC value of 125 µg/mL, against Shigella dysenteria. The present study, conclude that this species could be a promising source of antioxidant and antibacterial constituents.

Three new 30-norfriedelane and a new friedelane triterpenes from the trunk bark of Caloncoba welwitschii (Oliv.) Gilg (Achariaceae).

Phytochemical investigation of the methanolic extract of the trunk bark of Caloncoba welwitschii (Oliv.) Gilg (Achariaceae) led to the isolation of four new compounds, including three new 30-norfriedelane triterpenes, welwitschiilactones D-F (1-3), one new friedelane triterpene, welwitschioic acid (4) as well as ten known compounds: stigmastane-3,6-dione (7), a mixture of ß-sitosterol and stigmasterol (6a and 6b), a mixture of ß-sitosterol and stigmasterol glucoside (11a and 11b), (2S,3S,4R,5R)-N-(1,3,4,5-tetrahydroxyndecan-2-yl)tetradecanamide (10), 1-O-ß-D-glucopyranosyl-(2S,3R,8E)-2-[(2'R)-2-hydroxylpalmitoylamino]-8-octadecene-1,3-diol (12), 3ß,21ß-dihydroxy-27-oxo-30-nor-(D:A)-friedo-olean-20(29))en-27,19α-lactone (8), 21ß-hydroxy-3,27-dioxo-30-nor-(D:A)-friedo-olean-20(29)-en-27,19α-lactone (9) and 2ß,21ß-dihydroxy-27-oxo-30-nor-(D:A)-friedo-olean-20(29)-en-27,19α-lactone (5). The structures of all the isolated compounds were determined by extensive spectroscopic analyses (1D and 2D NMR as well as ESI-MS). The relative configuration of the 20-oxymethine in 1 as well as that of 19-oxymethine in 2 and 3 has been established using the NOESY spectrum. In an experiment, a sample of welwitschiilactone C (5) was chemically modified through reduction reaction to give a new hemi-synthetic derivative namely 2ß,3ß,21ß-trihydroxy-30-nor-(D:A)-friedo-olean-20(29)-en-27,19α-lactone (5a).

First report of compounds from an Ancistrocarpus species: Triterpenoids from A. densispinosus Oliv. (Malvaceae).

The stem bark of Ancistrocarpus densispinosus Oliv. exhibited triterpenoids, including the rare fernane-type, fern-9(11)-ene-2α,3ß-diol (1) a possible chemotaxonomically distinct biomolecule for the genus. Other triterpenoids that were isolated from this plant include the ursane-type ursolic acid (2) and corosolic acid (3), friedelane-type friedelin (4) and canophyllol (5), lupane-type lupeol (6), betulin (7), betulinic acid (8) and hennadiol (9), oleanoic acid (10), maslinic acid (11) and taraxerol (12) and three sterols. This is the first report of the chemistry of a plant of the Ancistrocarpus. The structures of the compounds were elucidated based on their NMR, IR and MS techniques and by comparisons of their experimental data with those reported. The twelve triterpenoids 1-12 were found to be inactive against five bacterial strains Escherichia coli, Bacillus subtilis, Pseudomonas agarici, Micrococcus luteus and Staphylococcus warneri; inactive against KB-3-1 cervix carcinoma cancer cell line and inactive as antioxidants in the DPPH assay.

New bioactive monoterpene indole alkaloid from Rinorea yaundensis Engl.

Extraction of the aerial part of Rinorea yaundensis has led to the isolation of a new monoterpene indole alkaloid (1) along with 10 known compounds (2-11) for the first time from this plant. Their structures were determined by HRMS and NMR spectroscopic analyses as yaundentine hydrochloride (1), Nb-oxide of iso-reserpiline (2), iso-reserpiline (3), iso-carapanaubine (4), lichenxanthone (5), stigmastane-3,6-dione (6), methyl ß-orcinol carboxylate (7), ß-sitosterol-3-O-ß-D-glucoside (8), betulinic acid (9), ursolic acid (10) and benzoic acid (11) while the stereochemistry and absolute configuration of 1 was confirmed by single crystal x-ray crystallography and circular dichroism CD spectrum. Yaundentine hydrochloride (1) exhibited pronounced antioxidant, urease and lipoxygenase inhibitory activities with IC50 values of 35.6 ± 0.23, 20.3 ± 0.58 and 29.6 ± 0.77 µM, respectively. Compound 1 also showed good antimicrobial activity against some Gram positive and negative bacteria.

Bioactive constituents from Manilkara obovata (Sabine & G.Don) J.H.Hemsl.

The phytochemical investigation of the methanolic extracts of roots, stem bark, leaves and twigs of Manilkara obovata has led to the isolation of one new friedelane triterpene, lacefriedelic acid or 3ß,23-dihydroxy D:A-friedooleanan-28-oic acid (1) and one new prenylated xanthone, lacexanthone or 4,7-dihydroxy-2,3,3,9,9-pentamethyl-2,2-dihydrofurano[2,3-a]pyrano[2,3-i]xanthen-13(9H)-one (2) alongside twenty-four known compounds. Compounds 1-11 are reported here for the first time from the genus Manilkara. The structures of all compounds were determined by spectroscopic analyses and X-ray crystallography. The methanolic extracts of twigs and leaves showed anti-oxidant activity of 93.2 and 91.1%, respectively, at 100 µg/mL when measured by DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate), while the twig extract displayed 86.3% at 100 µg/mL against the urease inhibition assay. Some isolated compounds (1-4, 15 and 20) showed significant to moderate anti-oxidant activity and urease inhibition assay. It is estimated that significantly active anti-oxidants and urease inhibitors metabolized by the plant may find future application in food industry.

Cytotoxic Stilbenes and Canthinone Alkaloids from Brucea antidysenterica (Simaroubaceae).

A phytochemical study of the root and bark of Brucea antidysenterica J. F. Mill. (Simaroubaceae) afforded three new compounds, including a stilbene glycoside bruceanoside A (1), and two canthinone alkaloids bruceacanthinones A (3) and B (4), along with ten known secondary metabolites, rhaponticin (2), 1,11-dimethoxycanthin-6-one (5), canthin-6-one (6), 1-methoxycanthin-6-one (7), 2-methoxycanthin-6-one (8), 2-hydroxy-1,11-dimethoxycanthin-6-one (9), ß-carboline-1-propionic acid (10), cleomiscosin C (11), cleomiscosin A (12), and hydnocarpin (13). The structures of all the compounds were determined using spectrometric and spectroscopic methods including 1D and 2D NMR, and HRSEIMS. The identities of the known compounds were further confirmed by comparison of their data with those reported in the literature. The root and bark methanolic extracts, the dichloromethane and ethyl acetate soluble fractions, and the isolated compounds (3-13), were assessed for their cytotoxicity against the cancer cell lines A-549, MCF-7, and PC-3. The results suggested that compounds in the extracts might possess a synergic action in their cytotoxicity.

A rotameric tryptamide alkaloid from the roots of Vepris lecomteana (Pierre) Cheek & T. Heller (Rutaceae).

A rotameric tryptamide alkaloid (1a-1b) was isolated from the methanolic extract of the roots of Vepris lecomteana together with the known compounds anhydroevoxine (2), lecomtequinoline C (3), evoxine (4), N-methylflindersine (5), evoxanthine (6), hesperidin, lupeol, ß-sitosterol and stigmasterol. The previously not reported 7-(3-anilino-2-hydroxyprenyloxy)-8-methoxydictamine (2a) was obtained by opening the epoxide of anhydroevoxine (2). The structures of above compounds were determined by comprehensive spectroscopic analyses of 1D and 2D NMR, EI-/ESI-MS, X-ray crystallography and comparison with the reported data. At room temperature, 1H and 13C NMR spectra show two rotamers (1a and 1b) with integrated intensities of 2/3, whereas at around 60 °C, only the 1b conformer was observed. Furthermore, the crystal structure of 1 was determined by the direct method of single crystal X-ray diffraction. The suggested biosynthesis for the formation of the new rotameric tryptamide alkaloid 1 is presented. Some of the isolated compounds (1, 2 and 2a) were tested in vitro against bacteria, resulting in weak for (1 and 2) to moderate activity for (2a) against Micrococcus luteus and Escherichia coli with MIC values of 15.3 and 15.3 µg/mL, respectively.

Oxidative burst inhibition, cytotoxicity and antibacterial acriquinoline alkaloids from Citrus reticulate (Blanco).

Two novel acridone-quinoline alkaloids, acriquinoline A (1) and acriquinoline B (2), together with twenty-two known compounds were isolated from the methanol extract of the root of Citrus reticulata Blanco. The structures of all compounds were determined by comprehensive analyses of their 1D and 2D NMR and mass spectral (EI and ESI) data. The possible biosynthesis for the formation of above compounds is proposed, based on close examination of their structures. Compounds 1, 2, 6, 10 and 14-17 exhibited strong suppressive effect on phagocytosis response upon activation with serum opsonized zymosan in the range of IC50 0.2-10.5µM, which was tested in vitro for oxidative burst studies of whole blood. However, compounds displayed low cytotoxic activity against the human Caucasian prostate adenocarcinoma cell line PC-3, with IC50 between 30.8 and 60.5µM compared to the standard doxorubicin with IC50 0.9µM. These compounds, tested against bacteria, fungi and plant pathogen oomycetes by the paper disk agar diffusion assay, resulting in missing to low activities corresponding with MICs>1mg/mL.

Afzeliixanthones A and B, two new prenylated xanthones from Garcinia afzelii ENGL. (Guttiferae).

Two new prenylated xanthones, afzeliixanthones A (1) and B (2), together with three known xanthones (3-5) and two phytosterols, beta-sitosterol and stigmasterol, were isolated from the CH2Cl2/MeOH (1:1) extract of the stem bark of Garcinia afzelii ENGL. collected in the South West Province of Cameroon. Structures were mainly established using one and two-dimensional NMR and mass spectroscopies. The antioxidant activities of the crude extracts as well as the new compounds (1) and (2) were evaluated.

Alpha-glucosidase inhibitory and antioxidant acridone alkaloids from the stem bark of Oriciopsis glaberrima ENGL. (Rutaceae).

The CH2Cl2/MeOH extract of the stem bark of Oriciopsis glaberrima ENGL. afforded four new acridone alkaloids namely oriciacridone C, D, E and F along with six known compounds: atalaphyllidine, oleanolic acid, butulinic acid, beta-sitosterol, stigmasterol, glucoside of stigmasterol and one synthetically known acridone: 1,3,5-trihydroxy-4-prenylacridone. The structures were established on the basis of MS, 1D and 2D NMR experiments. The acridones 1, 4 and 5 showed potent activity against alpha-glucosidase, while the acridones 1-5 showed moderate free radical scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH).

Alkaloids from Oriciopsis glaberrima Engl. (Rutaceae).

Two alkaloid derivatives, oriciacridone A and B, were isolated from the stem bark of Oriciopsis glaberrima (Rutaceae). The structures were elucidated by a detailed spectroscopic analysis. The extract exhibited in vitro significant antimicrobial activity against a range of micro-organisms.