Emmanuel Ngeufa Happi

Prenylated flavones and phenylpropanoid derivatives from roots of Dorstenia psilurus

Abstract Two new flavones, dorsilurins A and B, and a new benzofuran derivative have been isolated from Dorstenia psilurus , together with three known phenylpropanoid derivatives, stearyl- p -coumarate[octadecanyl 3-(4-hydroxyphenyl)prop-2-enoate], stearyl ferulate [octadecanyl 3-(4-hydroxy-3-methoxyphenyl)prop-2-enoate] and psoralen. The structures of new compounds were determined from spectroscopic data.

O-Prenylated Acridone Alkaloids from the Stems of Balsamocitrus paniculata (Rutaceae)

Two new O-prenylated acridone alkaloids, balsacridone A (1) and B (2), together with eighteen known compounds were isolated from the methanol extract from the stems of Balsamocitrus paniculata, a Cameroonian medicinal plant. The structures of all compounds were determined by comprehensive analyses of their 1D and 2D NMR, mass spectral (EI and ESI) data, and chemical reactions. N-methyl-6-methoxybenzoxazolinone (16) was isolated for the first time from a natural source while compounds 13, 14, and 15 for the first time from this genus. Pure compounds were tested for their activity against bacteria, fungi, and plant pathogen oomycetes, using the paper disk agar diffusion assay. The agar diffusion test delivered low to missing antimicrobial activities, corresponding to MICs > 1 mg/mL. However, compounds 1-15 exhibited a strong suppressive effect on phagocytosis response upon activation with serum opsonized zymosan in the range of IC50 = 0.5-7.2 μM, and the acridone alkaloids (1-5), N-trans-p-coumaroyltyramine (13), and N-trans-pcoumaroyloctopamine (14) displayed weak cytotoxic activity against the human Caucasian prostate adenocarcinoma cell line PC-3, with IC₅₀ values ranging from 69.8 to 99.0 μM.

Bioactive β-indoloquinazoline alkaloids from Oricia renieri.

Three new β-indoloquinazoline alkaloids, orirenierine A (1), B (2) and C (4), together with eleven known compounds were isolated from the methanol extract of the stems of Oricia renieri. The structures of all compounds were determined by comprehensive analyses of their spectroscopic data and comparison with literature information. The alkaloids 9-11 were isolated for the first time from this genus. All compounds were tested for their activity against bacteria, fungi, and plant pathogen oomycetes using the paper disk agar diffusion assay. The agar diffusion test gave only low antimicrobial activities, corresponding to MICs > 1 mg/mL. However, compounds 1-4 and 11 exhibited a strong suppressive effect on phagocytosis response upon activation with serum opsonized zymosan in the range of IC(50) = 2.6-6.5 µM, while low cytotoxic activity against the human Caucasian prostate adenocarcinoma cell line PC-3 was observed with IC(50) values ranging from 22.9 to 39.4 µM.

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.

Bioactive phenylethanoids and coumarines from Basalmocitrus cameroonensis.

Two new phenylethanoids, basalethanoid A (1) and B (2), and one new ceramide, basalamide A (3), together with eleven known compounds (4 - 14) were isolated from theMeOH extract of the stem barks of Basalmocitrus cameroonensis. The structures of all compounds were determined by comprehensive analyses of their 1D and 2D NMR, mass spectral (EI and ESI) data, chemical reactions, and comparison with previously known analogs. Compounds 1, 2, 5, and 7 - 10 demonstrated a strong inhibition on reactive oxygen species (ROS) production in the oxidative burst activity of whole blood on activation with serum opsonized zymosan in the range of IC50 = 0.06 - 12.30 μg mL−1. Graphical Abstract Bioactive Phenylethanoids and Coumarines from Basalmocitrus cameroonensis

Oxidative Burst Inhibitory and Cytotoxic Activity of Constituents of the Fruits of Odyendyea gabonensis

The methanol extract of dried fruits of Odyendyea gabonensis afforded one new quassinoid [(-)-odyendanol (1)], one new canthin-6-one alkaloid [9-hydroxy-5-methoxycanthin-6-one (4)], and two new steroids [22E, 24R-stigmasta-5,22-diene-3,7-dione (7) and 22E,24R-stigmast-22-ene-3,7-dione (8)] along with fourteen known compounds. The structures of all compounds were established by analyzing the spectroscopic data. The ¹³C-NMR values of (-)-odyendene (2) and (-)-odyendane (3), as well as the single-crystal X-ray structure of 5-methoxycanthin-6-one (6) are also reported.The oxidative burst inhibitory activity of pure compounds 1-12 was determined by the chemoluminescence assay, and cytotoxic activities of compounds 2-6 against the human prostate cancer cell PC-3 line were evaluated. Compounds 1-6 exhibited a clear suppressive effect on the phagocytosis response upon activation with serum-opsonized zymosan in the range of IC₅₀ = 0.9-2.0 µM versus ibuprofen with IC₅₀ = 12.1 µM, while all canthin-6-one alkaloids (4-6) displayed moderate cytotoxic activity against the human prostate cancer cell PC-3 line, with IC₅₀ values ranging from 13.5-15.4 µM versus doxorubicine with IC₅₀ = 1.5 µM.

Antimicrobial Furoquinoline Alkaloids from Vepris lecomteana (Pierre) Cheek & T. Heller (Rutaceae)

Three new prenylated furoquinoline alkaloids named lecomtequinoline A (1), B (2), and C (3), together with the known compounds anhydroevoxine (4), evoxine (5), dictamnine (6), N-methylflindersine (7), evoxanthine (8), hesperidin, lupeol, β-sitosterol, stigmasterol, β-sitosterol-3-O-β-d-glucopyranoside, stearic acid, and myristyl alcohol, were isolated by bioassay-guided fractionation of the methanolic extracts of leaves and stem of Vepris lecomteana. The structures of compounds were determined by spectroscopic methods (NMR, MS, UV, and IR) and by comparison with previously reported data. Crude extracts of leaves and stem displayed high antimicrobial activity, with Minimum Inhibitory Concentration (MIC) (values of 10.1–16.5 and 10.2–20.5 µg/mL, respectively, against Escherichia coli, Bacillus subtilis, Pseudomonas agarici, Micrococcus luteus, and Staphylococcus warneri, while compounds 1–6 showed values ranging from 11.1 to 18.7 µg/mL or were inactive, suggesting synergistic effect. The extracts may find application in crude drug preparations in Western Africa where Vepris lecomteana is endemic, subject to negative toxicity results in vivo.

A prenylated acridone alkaloid and ferulate xanthone from barks of Citrus medica (Rutaceae)

Abstract A new prenylated acridone alkaloid, medicacridone (1), and a new ferulate xanthone, medicaxanthone (5), together with 11 known compounds were isolated from the methanol extract of the bark of the Cameroonian medicinal plant Citrus medica. The structures of all compounds were determined by comprehensive analyses of their 1D and 2D NMR, mass spectral (EI and ESI) data, chemical reactions, and comparison with previously known analogues. The agar diffusion test delivered low to missing antimicrobial activities, corresponding with MICs > 1 mg mL–1, while compounds 1–6 and atalantoflavone (9) displayed weak cytotoxic activity against the human Caucasian prostate adenocarcinoma cell line PC-3, with IC50 values ranging from 60.5 to 80.0 μm versus doxorubicine with IC50=0.9 μm.

Steroids and Ceramide from the Stem Bark of Odyendyea gabonensis

Two new steroids, 22E, 24R-stigmast-22-ene-3,6,11-trione (1) and 22E, 24R-3-acetylstigmasta- 5,22-diene-7,11-dione (2), and one new ceramide, (2S,3S,4R,5R) N-(1,3,4,5-tetrahydroxyundecan- 2-yl)tetradecanamide (7), together with eleven known compounds were isolated from the CH2Cl2 extract of the stem bark of Odyendyea gabonensis. The structures of all compounds were determined by comprehensive analyses of their 1D and 2D NMR, mass spectral (EI and ESI) data, chemical reactions, and comparison with previously known analogs. Pure compounds were tested for their activity against the bacteria Bacillus subtilis, Staphylococcus aureus and Escherichia coli, the fungi Mucor miehei and Candida albicans, and the plant pathogen oomycetes Aphanomyces cochlioides, Pythium ultimum and Rhizoctonia solani using the paper disk agar diffusion assay. For active compounds, MICs were determined by the broth microdilution assay. Cytotoxic activity against the human lung adenocarcinoma cell line A 549 was evaluated by the MTT assay. All compounds delivered low to missing antimicrobial activities in the agar diffusion assay and MICs > 1 μg mL-1. The alkaloids 10 and 11 displayed cytotoxic activity against the human lung adenocarcinoma cell line A549 with IC50 2.5 and 4:5 μm respectively. Graphical Abstract Steroids and Ceramide from the Stem Bark of Odyendyea gabonensis