Indolosesquiterpene alkaloids from the Cameroonian medicinal plant Polyalthia oliveri (Annonaceae)

The stem bark of Polyalthia oliveri was screened for its chemical constituents using liquid chromatography high resolution mass spectrometry resulting in the isolation of three indolosesquiterpene alkaloids named 8α-polyveolinone (1), N-acetyl-8α-polyveolinone (2) and N-acetyl-polyveoline (3), together with three known compounds, dehydro-O-methylisopiline (4), N-methylurabaine (5) and polycarpol (6). The structures of the compounds were elucidated by means of high resolution mass spectrometry and different NMR techniques and chemical transformations. Their absolute configurations were assigned by ab-initio calculation of CD and ORD data (for 2 and 3) and X-ray diffraction analysis (for 2). Compounds 2 and 3 exhibited moderate antiplasmodial activity against erythrocytic stages of chloroquine-sensitive Plasmodium falciparum NF54 strain and low cytotoxicity on rat skeletal myoblast (L6) cell line.

Isolation and characterization of six labdane diterpenes and one pregnane steroid of Turraeanthus africanus

Six labdane diterpene derivatives, named turraeanins F-J (3-6, 8) and epi-turraeanin J (7), and a pregnane steroid derivative named turraeasterodionene (2), were isolated by preparative high performance liquid chromatography together with thirteen known compounds from the Cameroonian medicinal plant Turraeanthus africanus. Their structures were elucidated by means of nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry in conjunction with the published data for the analogs, as well as the fragmentation patterns of each compound. Most of the known compounds were obtained for the first time from this plant. The compounds (2-7) were tested for their antibacterial efficacies against both Gram-positive and Gram-negative bacteria, including some clinically-important Risk group 2 human pathogens. Compound 4 exhibited the most pronounced antibacterial effectiveness comparable to standard reference streptomycin, with more potency against Gram-positive than Gram-negative bacteria. By comparing compounds 3, 4 and 5, a tentative structure-activity relationship could be drawn; selected oxidations at C-16 and C-18 drastically reduced the antibacterial efficacy of the parent compound (4). These results revealed the potential of compound 4 as a suitable antibacterial lead compound that might be used for further development of other derivatives to increase the antimicrobial efficacy.

Steroidal saponins from Dioscorea preussii

Three new steroidal saponins, named diospreussinosides A-C (1-3), along with two known ones (4, 5) were isolated from rhizomes of Dioscorea preussii. Their structures were elucidated mainly by 1D and 2D NMR spectroscopic analysis and mass spectrometry as (25S)-17α,25-dihydroxyspirost-5-en-3β-yl-O-α-L-rhamnopyranosyl-(1→4)-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranoside (1), (25S)-17α,25-dihydroxyspirost-5-en-3β-yl-O-α-L-rhamnopyranosyl-(1→4)-α-L-rhamnopyranosyl-(1→4)-[α-L-rhamnopyranosyl-(1→2)]-β-D-glucopyranoside (2), and (24S,25R)-17α,24,25-trihydroxyspirost-5-en-3β-yl-O-α-L-rhamnopyranosyl-(1→4)-α-L-rhamnopyranosyl-(1→4)-[α-L-rhamnopyranosyl-(1→2)]-β-D-glucopyranoside (3). The spirostane-type skeleton of compound 3 possessing an unusual dihydroxylation pattern on the F-ring is reported for the first time. Cytotoxicity of compounds 2-5 was evaluated against two human colon carcinoma cell lines (HT-29 and HCT 116).

A Polyketide Metabolite from an Endophytic Fusarium equiseti in a Medicinal Plant

A new polyketide, fusaequisin A (1), was isolated from rice cultures of Fusarium equiseti SF-3-17, an endophytic fungus previously discovered during screening of medicinal plants in Cameroon. The structure of 1 was determined using spectroscopic methods. Fusaequisin A (1) exhibited moderate antimicrobial activity against Staphylococcus aureus NBRC 13276 and Pseudomonas aeruginosa ATCC 15442 at a concentration of 200 μg per disk.

Antimicrobial action mechanism of flavonoids from Dorstenia species

Naturally occurring flavonoids have been reported to possess antimicrobial activity against a wide range of pathogens. However, the antimicrobial action mechanism of these compounds has not yet been elucidated. This study investigated the mechanism underlying the antibacterial activity of four flavonoids: 6,8-diprenyleriodictyol (1), isobavachalcone (2), 6-prenylapigenin (3) and 4-hydroxylonchocarpin (4). In addition, the toxicity of these compounds was evaluated. Determination of the minimum inhibitory concentrations (MICs) was performed by microbroth dilution method. Radiolabeled thymidine, uridine, and methionine were used to evaluate the effect of the compounds on the biosynthesis of DNA, RNA, and proteins while the sensitive cyanine dye DiS-C3-(5) (3,3'-dipropylthiadicarbocyanine iodide) was used for the effect on membrane potential. Bactericidal/bacteriolysis activities were performed by time-kill kinetic method. In the toxicity study, the numbers of survivors was recorded after injection of compounds into the hemolymph of silkworm larvae. Compounds showed significant antibacterial activity against Staphylococcus aureus including methicillin-resistant S. aureus (MRSA) strains with MICs values ranged between 0.5-128 μg/mL. Depolarization of membrane and inhibition of DNA, RNA, and proteins synthesis were observed in S. aureus when treated with those flavonoids. At 5-fold minimum inhibitory concentration, compounds reduced rapidly the bacterial cell density and caused lysis of S. aureus. Compounds 1, 2, and 4 did not show obvious toxic effects in silkworm larvae up to 625 μg/g of body weight. Flavonoids from Dorstenia species, 6,8-diprenyleriodictyol, isobavachalcone, and 4-hydroxylonchocarpin are bactericidal compounds. They cause damage of cell membrane, leading to the inhibition of macromolecular synthesis. Taking into account the in vivo safety and their significant antimicrobial potency, these flavonoids are promising leads for further drug development.

Secondary Metabolites from Polar Fractions of Piper umbellatum

Seven known secondary metabolites were isolated from the methanol extract of the branches of Piper umbellatum. The identification of these compounds was mainly achieved by 2D NMR spectroscopic techniques and FAB-MS. Among them, the known cepharadiones A and B can be considered as chemotaxonomic markers of the genus Piper.

Triterpenoid saponins from Hydrocotyle bonariensis Lam

Phytochemical investigation of the under-ground parts of Hydrocotyle bonariensis led to the isolation of five oleanane-type triterpenoid saponins, 3-O-{β-D-glucopyranosyl-(1 → 2)-[α-L-arabinopyranosyl-(1 → 3)]-β-D-glucuronopyranosyl}-21-O-(2-methylbutyroyl)-22-O-acetyl-R(1)-barrigenol, 3-O-{β-D-glucopyranosyl-(1 → 2)-[α-L-arabinopyranosyl-(1 → 3)]-β-D-glucuronopyranosyl}-21-O-(2-methylbutyroyl)-28-O-acetyl-R(1)-barrigenol, 3-O-{β-D-glucopyranosyl-(1 → 2)-[α-L-arabinopyranosyl-(1 → 3)]-β-D-glucuronopyranosyl}-21-O-acetyl-R(1)-barrigenol, 3-O-{β-D-glucopyranosyl-(1 → 2)-[α-L-arabinopyranosyl-(1 → 3)]-β-D-glucuronopyranosyl}-R(1)-barrigenol, and 3-O-{β-D-glucopyranosyl-(1 → 2)-[α-L-arabinopyranosyl-(1 → 3)]-β-D-glucuronopyranosyl}-22-O-(2-methylbutyroyl)-A(1)-barrigenol, together with the known saniculoside-R1. Their structures were established by 2D NMR techniques and mass spectrometry. Six compounds were evaluated against two human colon cancer cell lines, HCT 116 and HT-29. Two compounds showed weak cytotoxicity with IC(50) 24.1 and 24.0, 83.0 and 83.6 μM against HT-29 and HCT 116, respectively.

Phenol esters and other constituents from the stem barks of Stereospermum acuminatissimum

A new ester, 2-(4'-hydroxyphenyl)ethyl dotriacontanoate (1), and a new inseparable mixture of octacosan-1,28-dioldiferulate and triacontan-1,30-dioldiferulate (2) were isolated from the stem barks of Stereospermum acuminatissimum, along with 24 known compounds including 4 triterpenoids, 11 anthraquinones, 2 lignans, 3 phenylpropanoids, 2 4-hydroxyphenethyl esters, 1 methoxyphenol, and 1 iridoid. The structures of the new metabolites were determined with the help of spectroscopic data including extensive 2D NMR spectroscopy. The known compounds were identified by comparison of their physical and spectroscopic data with those reported in the literature. The compounds were tested against Candida albicans ATCC 24433, C. albicans ATCC 90028, Candida glabrata ATCC 90030, Candida krusei ATCC 6258, and Candida parapsilosis ATCC 22019. Some of them were moderately active.

A new fatty aldol ester from the aerial part of Mimosa invisa (Mimosaceae)

A new aldol ester named 17-O-triacontanoylheptadecanal (1) was isolated from the aerial part of Mimosa invisa (Mimosaceae) together with eight known compounds identified as β-sitosterol (2), α-amyrine (3), lupeol (4), 4'-O-methylepinumisoflavone (5), alpinumisoflavone (6), betulinic acid (7), 3-O-β-D-glucopyranoside of sitosterol (8) and epirobinetinidol (9). The structures of compounds were determined on the basis of NMR and mass spectrometry data as well as by comparing the data reported in the literatures. The antimicrobial activities of the crude extract and compounds 1 and 9 were investigated against seven microbial species. The natural products showed moderate activities compared to that of the crude extract.

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.

Traditional medicine: past, present and future research and development prospects and integration in the National Health System of Cameroon

Traditional medicine refers to health practices, approaches, knowledge and beliefs incorporating plant, animal and mineral based medicines, spiritual therapies, manual techniques and exercises, applied singularly or in combination to treat, diagnose and prevent illnesses or maintain well-being. In the last decade traditional medicine has become very popular in Cameroon, partly due to the long unsustainable economic situation in the country. The high cost of drugs and increase in drug resistance to common diseases like malaria, bacteria infections and other sexually transmitted diseases has caused the therapeutic approach to alternative traditional medicine as an option for concerted search for new chemical entities (NCE). The World Health Organisation (WHO) in collaboration with the Cameroon Government has put in place a strategic platform for the practice and development of TM in Cameroon. This platform aims at harmonizing the traditional medicine practice in the country, create a synergy between TM and modern medicine and to institutionalize a more harmonized integrated TM practices by the year 2012 in Cameroon. An overview of the practice of TM past, present and future perspectives that underpins the role in sustainable poverty alleviation has been discussed. This study gives an insight into the strategic plan and road map set up by the Government of Cameroon for the organisational framework and research platform for the practice and development of TM, and the global partnership involving the management of TM in the country.

A cocrystal of 3α-hy-droxy-tirucalla-8,24-dien-21-oic acid and 3β-fluoro-tirucalla-7,24-dien-21-oic acid (0.897:0.103)

The title compound, 0.897C₃₀H₄₈O₃.0.103C₃₀H₄₇O₂F is a co-crystal of two triterpenes isolated from the resin of Canarium schweinfurthiiand Engl. Both triterpenes consists of four trans-fused rings having chair/half-chair/half-chair and envelope conformations. The mol­ecular conformations are stabilized by intra­molecular C—H⋯O hydrogen bonds, forming rings of S(7) graph-set motif. In the crystal, mol­ecules are linked by inter­molecular O—H⋯O and C—H⋯O inter­actions, forming sheets parallel to (001). All atoms. excepting the axially-oriented hydroxyl group in the major component and the equatorially-oriented fluorine atom in the minor component, are overlapping.

3α-Hy-droxy-tirucalla-8,24-dien-21-oic acid

The title compound, C₃₀H₄₈O₃, a triterpene isolated from the resin of canarium schweinfurthiiand, is an isomer of the previously reported triterpene 3α-hy­droxy­tirucalla-7,24-dien-21-oic acid [Mora et al. (2001 ▶). Acta Cryst. C57, 638–640], which crystallizes in the same trigonal space group. The title mol­ecule consists of four fused rings having chair, half-chair, half-chair and envelope conformations for rings A, B, C and D, respectively (steroid labelling). An intra­molecular C—H⋯O hydrogen bond generates an S(7) ring. In the crystal, mol­ecules are linked by O—H⋯O and C—H⋯O inter­actions, forming (001) sheets.

A New Ceramide Isolated from Ficus lutea Vahl (Moraceae)

In addition to benjaminamide (2), β-amyrin, β-amyrin acetate, lupeol, betulinic acid, β-sitosterol glucoside, a new ceramide glycoside was isolated from the woods of Ficus lutea Vahl (Moraceae). Using mass fragmentation pattern, 1 and 2D NMR spectra and by comparison with published data, the new compound was characterized as 1-O-β-D-glucopyranosyl-(2S,3R,5E,12E)-2N-[(2'R)-hydroxyhexadecanoyl]-octadecasphinga-5,12-dienine (1a) for which the trivial name lutaoside was proposed. Some isolated compounds were evaluated for their antimicrobial activities. Compounds 1a and 2 showed some antimicrobial activity.

Antimicrobial activity of the methanolic extract and compounds from Morus mesozygia stem bark

AIM OF THE STUDY

This study was aimed at investigating the antimicrobial activity of the methanolic extract (MMB) and compounds isolated from the stem bark of Morus mesozygia, namely 3beta-acetoxyurs-12-en-11-one (1), moracin Q (2), moracin T (3), artocarpesin (4), cycloartocarpesin (5), moracin R (6), moracin U (8), moracin C (9), and moracin M (10).

MATERIALS AND METHODS

The liquid microdilution assay was used in the determination of the minimal inhibitory concentration (MIC) and the minimal microbicidal concentration (MMC), against nine bacterial and two fungal species.

RESULTS

The results of the MIC determination showed that the compounds 3, 4, 8 and 9 were able to prevent the growth of all tested microbial species. All other samples showed selective activities. Their inhibitory effects were noted on 90.9% studied organisms for the crude extract, 81.8% for compound 6, 72.7% for compound 10, 63.6% for compound 1, 54.5% for compound 5, and 45.5% for compound 2. The lowest MIC value of 39 microg/ml was obtained with the crude extract against Escherichia coli. The corresponding value for compounds (5 microg/ml) was registered with compound 9 on Shigella dysenteriae and compound 3 on E. coli, S. dysenteriae, Pseudomonas aeruginosa, Salmonella typhi and Bacillus cereus. The lowest MIC value (39 microg/ml) observed with the crude extract (on E. coli) was only eightfold greater than that of gentamycin used as reference antibiotic (RA) while the corresponding value (5 microg/ml) recorded with compounds 3 and 9 was equal to that of RA on the corresponding microorganisms.

CONCLUSIONS

The obtained results highlighted the interesting antimicrobial potency of M. mesozygia as well as that of the studied compounds, and provided scientific basis for the traditional use of this species.

Antimicrobial activity of the crude extract, fractions and compounds from stem bark of Ficus ovata (Moraceae)

AIM OF THE STUDY

This study was designed to investigate the antimicrobial activities of the methanol extracts from the stem bark of Ficus ovata (FOB), fractions (FOB1-6) and compounds isolated following bio-guided fractionation [3-friedelanone (1), taraxeryl acetate (2), betulinic acid (3), oleanoïc acid (4), 2-hydroxyisoprunetin (5), 6,7-(2-isopropenyl furo)-5,2,4-trihydroxyisoflavone (6), Cajanin (7) and protocatechuic acid (8)].

MATERIALS AND METHODS

The micro-dilution method was used for the determination of the minimal inhibition concentration (MIC) and the minimal microbicidal concentration (MMC) against fungi (two species), gram-positive (three species) and gram-negative bacteria (five species).

RESULTS

The results of the MIC determinations indicated that the crude extract (FOB), fractions FOB2 and FOB4 as well as compound 5 were active on the entire studied organisms. Other samples showed selective activity, fractions FOB1, FOB3 and FOB5 being active against 50% of the tested microbial species while FOB6 was active on 40%. Compounds 8, 6, 2 and 7 prevented the growth of 80%, 70%, 50% and 20% of the organisms respectively. The lowest MIC value (156 g/ml) observed with the crude extract was recorded on Streptococcus faecalis, Candida albicans and Microsporum audouinii. The corresponding value for fractions (39 microg/ml) was noted with FOB4 against Staphylococcus aureus, while that of the tested compounds (10 microg/ml) was observed with compound 8 on Microsporum audouinii. The results of the MMC determination suggested that the cidal effect of most of the tested samples on the studied microorganisms could be expected.

CONCLUSIONS

The overall results provided evidence that the studied plant extract, as well as some of the isolated compounds might be potential sources of new antimicrobial drug.

Induction of Neuronal Differentiation in Neurosphere Stem Cells by Ellagic Acid Derivatives

A bioassay-guided fractionation of methanol extracts of stem barks, combined with screening based on Epidermal Growth Factor (EGF)-responsive neural stem cells (erNSCs) differentiation assay, has been used. This study resulted in the isolation of 3,3′-di- O-methylellagic acid 1, 3,3′-di- O-methyl ellagic acid-4- O-β-D-xylopyranoside 2, ellagic acid 3, and arjunolic acid 4. Among them, compounds 1 and 2 exhibit potent induction of neuronal differentiation in neurosphere stem cells with no cytotoxic effect. These results indicate that compounds 1 and 2 may be useful as pharmacological agents for the treatment of neurodegenerative diseases. These compounds may account, for the use of T. superba in folk medicine for nervous system and mental disorders.

Antimicrobial pentacyclic triterpenoids from Terminalia superba

Antibacterial bioassay-guided fractionation of the methanol extract of the stem bark of Terminalia superba led to the isolation of four new triterpene glucosides (1-4) which were characterized as 2 alpha,3 beta-dihydroxyolean-12-en-28-oic acid 28-O-beta-D-glucopyranoside (1), 2 alpha,3 beta, 21 beta-trihydroxyolean-12-en-28-oic acid 28-O-beta-D-glucopyranoside (2), 2 alpha,3 beta, 29-trihydroxyolean-12-en-28-oic acid 28-O-beta-D-glucopyranoside (3) and 2 alpha,3 beta,23,27-tetrahydroxyolean-12-en-28-oic acid 28-O-beta-D-glucopyranoside (4) together with the known triterpene 2 alpha,3 beta,23-trihydroxyolean-12-en-28-oic acid (5). Structures were established by spectroscopic methods including one- and two-dimensional NMR, EI-MS and HR-EI-MS. The antibacterial activity of 1-5 was also investigated against two gram-positive (Bacillus subtilis, Staphylococcus aureus), and four gram-negative (Escherichia coli, Shigella flexenari, Pseudomonas aeruginosa, Salmonella typhi) bacterial strains.

Induction of neuronal differentiation in neurosphere stem cells by ellagic acid derivatives

A bioassay-guided fractionation of methanol extracts of stem barks, combined with screening based on Epidermal Growth Factor (EGF)-responsive neural stem cells (erNSCs) differentiation assay, has been used. This study resulted in the isolation of 3,3'-di-O-methylellagic acid 1, 3,3'-di-O-methyl ellagic acid-4-O-beta-D-xylopyranoside 2, ellagic acid 3, and arjunolic acid 4. Among them, compounds 1 and 2 exhibit potent induction of neuronal differentiation in neurosphere stem cells with no cytotoxic effect. These results indicate that compounds 1 and 2 may be useful as pharmacological agents for the treatment of neurodegenerative diseases. These compounds may account, for the use of T. superba in folk medicine for nervous system and mental disorders.