Binding of Mammea A/AA (MA) to calf thymus DNA revealed by the ratiometric absorbance of MA in the UV-visible range molecular dynamic simulations and TD-DFT calculations.

The in vitro anti-proliferative activity of MA (5,7-dihydroxy-8-(3-methylbut-2-enyl)-6-(3-methyl-1-oxobutyl)-4-phenyl[1]2H-[1]benzopyran-2-one)on a variety of cancer cells was previously demonstrated. This work strives to understand the mechanisms by which MA exerts this biological activity. Thereafter, the binding of MA to calf thymus DNA was studied by monitoring the change in the UV-visible absorbance of MA. It was found that, the response of MA to binding with calf thymus DNA is characterised by an increase in the AS/AL ratio of the absorbance of the longest wavelength absorption band to the shortest one, and the appearance of a new band at about 377 nm assigned to S0→S1 transition, which is red shifted as compared to free MA. From the bands ratio, the binding constant is found to be 4.3x105 M-1, indicating strong binding. The deduced binding free energy, enthalpy and entropy are -7.7 kcal/mol, -10.89 ± 0.28 kcal/mol and -54.46 ± 4 J/K, respectively, indicating that MA binds to DNA by a non-bonding Van der Waals type interactions and hydrogen bonds. Further study with classical molecular dynamics shows that MA binds to DNA by intercalation, where it is positioned between two AT base pairs. Unlike isolated MA, TDDFT calculations on ten images extracted from the MD trajectory show that, the frontier molecular orbitals of the complex are distributed over the DNA and MA. This indicates a strong stacking interaction and then explains the hypochromism and the red shift of the S0→S1 transition. The present work demonstrates the potency of MA as antitumor compound and as absorbance-based molecular probe.Communicated by Ramaswamy H. Sarma.

Bioguided Fractionation and Isolation of an Antiplasmodial Saponin from the Roots of Nauclea xanthoxylon (A.Chev.) Aubrév. (Rubiaceae).

The root extract of Nauclea xanthoxylon (A.Chev.) Aubrév. displayed significant 50 % inhibition concentration (IC50 s) of 0.57 and 1.26 µg/mL against chloroquine resistant and sensitive Plasmodium falciparum (Pf) Dd2 and 3D7 strains, respectively. Bio-guided fractionation led to an ethyl acetate fraction with IC50 s of 2.68 and 1.85 µg/mL and subsequently, to the new quinovic acid saponin named xanthoxyloside (1) with IC50 s of 0.33 and 1.30 µM, respectively against the tested strains. Further compounds obtained from ethyl acetate and hexane fractions were the known clethric acid (2), ursolic acid (3), quafrinoic acid (4), quinovic acid (5), quinovic acid 3-O-ß-D-fucopyranoside (6), oleanolic acid (7), oleanolic acid 3-acetate (8), friedelin (9), ß-sitosterol (10a), stigmasterol (10b) and stigmasterol 3-O-ß-D-glucopyranoside (11). Their structures were characterised with the aid of comprehensive spectroscopic methods (1 and 2D NMR, Mass). Bio-assays were performed using nucleic acid gel stain (SYBR green I)-based fluorescence assay with chloroquine as reference. Extracts and compounds exhibited good selectivity indices (SIs) of >10. Significant antiplasmodial activities measured for the crude extract, the ethyl acetate fraction and xanthoxyloside (1) from that fraction can justify the use of the root of N. xanthoxylon in ethnomedicine to treat malaria.

Rotenoids and Isoflavones from Xeroderris stuhlmannii (Taub.) Mendonça & E.P. Souza and Their Biological Activities.

The phytochemical study of the ethanolic extract of the leaf of Xeroderris stuhlmannii led to the isolation of five hitherto unreported compounds including two isoflavones (1-2), and three rotenoids (3-5), along with eight known isoflavonoid derivatives (6-13) and one pterocarpan derivative (14). The structures of the new compounds and those of the known ones were established by the spectroscopic (1D and 2D NMR) and spectrometric (HRESIMS) techniques as well as a comparison of their spectroscopic data with those reported in the literature. The leaf extract, fractions, and isolated compounds were tested for their antibacterial effects against nine bacterial strains. Compounds 3, 8, 11, and 12 showed a significant antibacterial effect, with a minimum inhibitory concentration (MIC) value of 62.5 µg/mL each, against Salmonella typhi, Staphylococcus aureus, Klessiella pneumonae, and Escherichia coli, respectively. In addition, the leaf extract, fractions, and isolated compounds were tested for their antifungal effects against four fungal strains. The hexane fraction showed a significant antifungal effect with an MIC value of 125 µg/mL against Candida parasilosis, whereas compounds 3, 8, and 12 showed significant antifungal activity with an MIC value of 62.5 µg/mL, each against Candida parasilosis, Candida albicans, and Candida krusei, respectively.

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.

A New Aromatic Amide from the Roots of Zanthoxylum tessmannii (Rutaceae).

Phytochemical investigation of the methanolic extract of the roots of Zanthoxylum tessmannii Zepernick and Timler (Rutaceae) led to the isolation and characterization of one new aromatic amide named tessmamide (1) along with twelve known compounds, N-benzoyltyramine methyl ether (2), 7,8,9-trimethoxycoumarin (3), 7,8-dimethoxycoumarin (4), integrifoliodiol (5), robustin (6), skimmianine (7), lupeol (8), lupenone (9), a mixture of stigmasterol and ß-sitosterol, and a mixture of their glucosides. The structures of all compounds were determined by comprehensive spectroscopic analyses (1D- and 2D-NMR, EI-MS, and ESI-MS) and comparison with known analogs. The determination of the radical scavenging activity using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay gave moderate antioxidant values for the crude extracts of the roots of Zanthoxylum tessmannii (IC50 0.8 mg/mL), tessmamide (1; IC50 31.8 µm), and 7,8,9-trimethoxycoumarin (3; IC50 29.3 µm), compared to the standard ascorbic acid (IC50 11.6 µm).

In vitro effects of aqueous extract from Maytenus senegalensis (Lam.) Exell stem bark on egg hatching, larval migration and adult worms of Haemonchus contortus.

BACKGROUND: Maytenus senegalensis is a common shrub which is scattered in tropical Africa. Different parts of this plant have been reported to be useful in traditional medicine against gastrointestinal disorders and intestinal worms. This study evaluated the anthelmintic activity of the aqueous stem bark extract of M. senegalensis using egg hatch assay (EHA), larval migration inhibition assay (LMIA) and adult worms' motility inhibition assay (AMIA). RESULTS: On EHA, the extract concentrations tested resulted in a significant (p < 0.01) inhibition of egg hatching in concentration-dependent manner and ranged between 31.86% at 75 µg.mL- 1 to 54.92% at 2400 µg.mL- 1 after a 48 h post-exposure with eggs. For the LMI assays, the aqueous extract of M. senegalensis showed a significant (p < 0.05) inhibition of larval migration in a concentration-dependent manner. The highest concentration used (2400 µg.mL- 1) showed a 37.77% inhibition. The use of polyvinyl polypyrrolidone (PVPP) indicated that tannins and flavonoids were partly involved in the effect since the larval migration was inhibited by 15.5%, but other biochemical compounds were also implicated. On AMIA, M. senegalensis was associated with a reduced worm motility after a 24 h post exposure compared to phosphate buffered saline as control (p < 0.05). By this time 66.66% of the worms' were found immotile or dead in the wells containing plant extract at 2400 µg.mL- 1. The Phytochemical analysis of aqueous extract of M. senegalensis by HPLC-ESI-MSn detected the presence of proanthocyanidins (20%) and flavonoids (> 50%). CONCLUSIONS: These in vitro results suggest the presence of some anthelmintic properties in M. senegalensis extract, which is traditionally used by small farmers in west and central Africa. These effects may be due to the flavonoids and proanthocyanidins present in the extract and need to be studied under in vivo conditions.

Biological activities of plant extracts from Ficus elastica and Selaginella vogelli: An antimalarial, antitrypanosomal and cytotoxity evaluation.

The cytotoxic, antiplasmodial, and antitrypanosomal activities of two medicinal plants traditionally used in Cameroon were evaluated. Wood of Ficus elastica Roxb. ex Hornem. aerial roots (Moraceae) and Selaginella vogelii Spring (Selaginellaceae) leaves were collected from two different sites in Cameroon. In vitro cell-growth inhibition activities were assessed on methanol extract of plant materials against Plasmodium falciparum strain 3D7 and Trypanosoma brucei brucei, as well as against HeLa human cervical carcinoma cells. Criteria for activity were an IC50 value < 10 µg/mL. The extract of S. vogelii did not significantly reduce the viability of P. falciparum at a concentration of 25 µg/mL but dramatically affected the trypanosome growth with an IC50 of 2.4 µg/mL. In contrast, at the same concentration, the extract of F. elastica exhibited plasmodiacidal activity (IC50 value of 9.5 µg/mL) and trypanocidal (IC50 value of 0.9 µg/mL) activity. Both extracts presented low cytotoxic effects on HeLa cancer cell line. These results indicate that the selected medicinal plants could be further investigated for identifying compounds that may be responsible for the observed activities and that may represent new leads in parasitical drug discovery.

Voltammetric behavior of Mammeisin (MA) at a glassy carbon electrode and its interaction with Bovine Serum Albumin (BSA).

The electrochemical oxidation of Mammeisin (MA) was studied in a solution containing acetone and 0.1M phosphate buffer +0.1M KCl (pH=5.3) at a glassy carbon electrode (GCE), using cyclic (CV) and square wave voltammetry (SWV). MA showed a quasi-reversible process, which is pH dependent and that involves the exchange of two electrons and two protons. The oxidation product was adsorbed by the electrode surface to form a film that blocks active sites over repetitive cyclic. Moreover, the interaction of MA and bovine serum albumin (BSA) was studied by CV and SWV at different pHs (5.4, 7.2, 9.5). As a result of the affinity binding with BSA, electrochemically inactive complex was formed. In addition, the oxidation potential of MA in the presence of BSA depends on the pH. The diffusion coefficients of both free and bound MA were estimated from the cyclic voltammetry data using the method developed by Randles-Sevich (Df=9.85×10-5cm2s-1 and Db=1.27×10-9cm2s-1) and the binding constant of MA-BSA complex, K=3.47×102Lmol-1, was obtained.

Antinociceptive and anti-inflammatory effects of the methanolic stem bark extract of Antrocaryon klaineanum Pierre (Anacardiaceae) in mice and rat.

ETHNOPHARMACOLOGICAL RELEVANCE: Antrocaryon klaineanum is used by traditional healers to treat many disorders including pain and inflammatory diseases. This study aimed to evaluate the analgesic and antiinflammatory activities of methanol extract of A. klaineanum in mice and rats. MATERIALS AND METHODS: Reverse phase high-performance liquid chromatography (RP-HPLC) was performed to establish the chromatographic fingerprint and to identify various chemical components of the plant extract. The anti-nociceptive activity of methanol extract of A. klaineanum was assessed using the acetic acid-induced abdominal constriction model, formalin test, capsaicin and cinnamaldehyde induced-neurogenic pain and hot plate test. Anti-inflammatory activity was assessed on carrageenan-induced inflammation. Extract was administrated orally at 200, 400 and 600mg/kg. RESULTS: Phytochemical analysis indicated the presence of proanthocyanidins, phenolic acids and flavonoids. The results of anti-nociceptive and anti-inflammatory activities showed that methanol extract significantly (p<0.01) reduced the pain induced by acetic acid with an inhibition percentage of 45.49% (600mg/kg). In the formalin test, the extract also significantly (p<0.01) reduced linking time in both phase (neurogenic and inflammatory) of the test with inhibition percentage of 56.28% and 60.73% respectively at the dose of 600mg/kg. The methanol extract of A. klaineanum significantly (P<0.001) reduced neurogenic pain linking time induced by capsaicin and cinnamaldehyde by 82.54% and 75.94% at the highest dose (600mg/kg) respectively. More over the extract significantly increase the reaction time in hot plate test. In the inflammatory test, the plant extract significantly reduced the carrageen induced rat paw oedema from 30min to 6h with a maximum percentage inhibition of 89.88% (6h) at the dose of 600mg/kg. CONCLUSION: These results demonstrate that the methanol extract of A. klaineanum may possess analgesic and anti-inflammatory effects and provide support of the traditional use of this plant in the treatment of different pain and inflammatory conditions. Further investigation could reveal metabolites of the extract responsible for the observed effects.

The structure of antrocarine E, an ergostane isolated from Antrocaryon klaineanum Pierre (Anacardiaceae).

Eight compounds were isolated from the stem bark of Antrocaryon klaineanum, and their structures determined by chemical and spectroscopic methods. Among these compounds, the ergostane-type antrocarine E (1a) is a new compound, although the structure had already been published by mismatching the spectroscopic data with those of 2. In this paper, we are reporting the valid spectroscopic values for antrocarine E and X-ray diffraction results.

In vitro antimicrobial and anti-proliferative activities of plant extracts from Spathodea campanulata, Ficus bubu, and Carica papaya.

CONTEXT: African medicinal plants represent a prominent source of new active substances. In this context, three plants were selected for biological investigations based on their traditional uses. OBJECTIVE: The antimicrobial and anti-proliferative features of three plants used for medicinal purpose were evaluated. MATERIALS AND METHODS: The antimicrobial activities of methanol extracts of Ficus bubu Warb. (Moraceae) stem bark and leaves, of Spathodea campanulata P. Beauv. (Bignoniaceae) flowers, as well as those of Carica papaya Linn. (Caricaceae) latex, were determined using the microbroth dilution method against a set of bacteria and fungi pathogens including: Enterococcus faecalis, Staphylococcus aureus, S. saprophyticus, S. epidermididis, Escherichia coli, Klebsiella pneumonia, Salmonella typhimurium, Candida albicans, and Trichophyton rubrum. The tested concentrations of extracts ranged from 2500.0 to 2.4 µg/mL and MIC values were evaluated after 24 h incubation at 37 °C. Subsequently, MTT assay was used to estimate anti-proliferative activity of these methanol extracts and of F. bubu latex on three human cancer cell lines (U373 glioblastoma, A549 NSCLC, and SKMEL-28 melanoma). RESULTS: The methanol extract of F. bubu stem bark exhibited the highest antimicrobial activity against C. albicans with a MIC value of 9.8 µg/mL, while the F. bubu latex and the methanol extract of F. bubu leaves induced significant anti-proliferative activity against lung (IC50 values of 10 and 14 µg/mL, respectively) and glioma (IC50 values of 13 and 16 µg/mL, respectively) cancer cells. CONCLUSION: These results indicate that effective drugs could be derived from the three studied plants.

Antiplasmodial activity of some phenolic compounds from Cameroonians Allanblackia.

BACKGROUND: Plasmodium falciparum, one of the causative agents of malaria, has high adaptability through mutation and is resistant to many types of anti-malarial drugs. This study presents an in vitro assessment of the antiplasmodial activity of some phenolic compounds isolated from plants of the genus Allanblackia. METHODS: Tests were performed on well plates filled with a fixed parasitized erythrocytes volume. Compounds to be tested were then added in wells. After incubation, tritiated hypoxanthine is added and the plates were returned to the incubator. After thawing, the nucleic acids are collected. Inhibitory Concentration 50 (IC50) was determined by linear interpolation. RESULTS: From Allanblackia floribunda, have been isolated and characterized 1,7-dihydroxyxanthone 1, macluraxanthone 4, morelloflavone 9, Volkensiflavone 10 and morelloflavone 7-O-glucoside 11; from Allanblackia monticola, α-mangosine 2, rubraxanthone 3, allaxanthone C 5, norcowanine 6, tovophiline A 7, allaxanthone B 8 and from Allanblackia gabonensis, 1,7-dihydroxyxanthone 1. Six of them were evaluated for their antimalarial properties. The most active compound, macluraxanthone, presented a very interesting activity, with an IC50 of 0.36 and 0.27 µg/mL with the F32 and FcM29 strains respectively. CONCLUSION: This work confirms that species of Allanblackia genus are medicinally important plants containing many biologically active compounds that can be used effectively as antiplasmodial.

Antioxidant, antitumor and antimicrobial activities of the crude extract and compounds of the root bark of Allanblackia floribunda.

CONTEXT: Allanblackia floribunda Oliver (Guttiferae) is an African medicinal plant used traditionally to treat a variety of ailments. OBJECTIVE: We investigated the antitumor, radical scavenging, antimycobacterial, antibacterial and antifungal activities of the root bark extract of A. floribunda and three isolated phenolics, namely 1,7-dihydroxyxanthone (1), morelloflavone (2) and 7'-O-glucoside of morelloflavone (3). MATERIALS AND METHODS: The 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) radical scavenging assay was used for antioxidant tests, while crown gall tumor assay was used for assay of antitumor activity. The p-iodonitrotetrazolium chloride (INT) colorimetry and Microplate Alamar Blue Assay (MABA) were used for antimicrobial investigations. RESULTS: Moderate tumor reducing activity was observed with the extract, while better activities were recorded with compounds 2 and 3. The antimycobacterial and antitumor activities of the extract are being reported for the first time. The DPPH radical scavenging test showed that all the studied samples were able to scavenge more than 50% of the free radical, with compound 3 showing the best inhibitory activity (IC(50) of 49.08 µg/mL). Compounds 1 to 3 prevented the growth of Mycobacterium smegmatis and both extract and compound 2 were active on M. tuberculosis. The lowest MIC value for the extract (9.76 µg/mL) was recorded against Enterobacter aerogenes while the corresponding value for the compounds (4.88 µg/mL) was obtained with compound 2 on Trichophyton rubrum. DISCUSSION AND CONCLUSION: The overall results of the present work provide baseline information for the potential use of the root bark extract of A. floribunda as an antimicrobial, antitumor and antioxidant phytomedicine.

Pentacyclic triterpenoids and ceramide mediate the vasorelaxant activity of Vitex cienkowskii via involvement of NO/cGMP pathway in isolated rat aortic rings.

ETHNOPHARMACOLOGICAL RELEVANCE: Vitex cienkowskii Kotschy & Peyritsch is a deciduous tree, prescribed by Cameroonian traditional healers as one of the most popular plant widely used in many disorders including cardiovascular diseases. The preliminary pharmacological studies carried out on Vitex cienkowskii showed its vasorelaxant activities on guinea-pig aortic rings. AIM OF THE STUDY: The present work evaluated the vasorelaxant activity of extract and isolated compounds from Vitex cienkowskii. MATERIALS AND METHODS: Rat aortic rings were used to evaluate the in vitro vascular effect of the extract. The antioxidant activity was determined by measuring the reduction of the free radical 1,1-diphenyl-1-picryl-hydrazyl (DPPH). RESULTS: Vitex cienkowskii induced significant relaxation in a concentration- and endothelium-dependent manner (EC(50)=12.12 µg/ml, CH(2)Cl(2)-MeOH, 1:1) and did not produce a vasorelaxant effect on contraction evoked by KCl (60 mM). In order to determine its mode of action, Vitex cienkowskii-induced relaxant effect was evaluated in the presence of indomethacin (10 µM), L-NAME (100 µM), ODQ (1 µM) and SQ22356 (100 µM). Relaxation was significantly blocked by L-NAME and ODQ. These results indicate that Vitex cienkowskii-mediated relaxation is endothelium dependent, probably due to NO release, and the consequent activation of vascular smooth muscle soluble guanylate cyclase (sGC), a signal transduction enzyme that forms the second messenger cGMP. Bio-guided study of Vitex cienkowskii allowed the isolation of the known pentacyclic triterpenoids and a ceramide. It is the first report of salvin A, maslinic acid and a ceramide from Vitex cienkowskii. The activity induced by these compounds indicated that they may be partly responsible for the vasorelaxant effect of the plant extract. A dose of 40 mg/kg of CH(2)Cl(2)-MeOH (1:1) extract administered intravenously induced a decrease of mean arterial pressure but did not affect the heart rate. Moreover the plant extracts were found to be highly active in the DPPH radical scavenging assay. CONCLUSION: Vitex cienkowskii extract possesses antioxidant property, vasorelaxing, and hypotensive effect linked to the endothelium related factors, where nitric oxide is involved.

Xanthones from the seeds of Allanblackia monticola and their apoptotic and antiproliferative activities.

Phytochemical investigations of the seeds of ALLANBLACKIA MONTICOLA have led to the isolation and characterization of one new xanthone derivative, named allanxanthone E ( 1), together with seven known compounds, including five xanthones, 1,7-dihydroxy-3-methoxy-2-(3-methylbut-2-enyl)xanthone ( 2), alpha-mangostin ( 3) , garciniafuran ( 4) , allanxanthone C ( 5), and 1,6-dihydroxy-2,4-diprenylxanthone ( 6), and two pentacyclic triterpenes, friedelin and lupeol. The structures of these compounds were established on the basis of one- and two-dimensional NMR homo- and heteronuclear correlation evidence. Some of these compounds were evaluated for their apoptotic and antiproliferative activities against human leukemic B lymphocytes, such as the hairy cell leukemia-derived ESKOL cell line and cells from B-CLL (B-cell chronic lymphocytic leukemia) patients.

Anti-inflammatory and anti-nociceptive activities of the stem bark extracts from Allanblackia monticola STANER L.C. (Guttiferae).

THE AIM OF THIS STUDY: was to assess the anti-inflammatory and mechanism of action of Allanblackia monticola (Guttiferae). The anti-inflammatory activity "in vivo" of the methylene chloride/methanol extract, methanol and methylene chloride fractions of stem barks of Allanblackia monticola, administered orally at doses of 37.5; 75; 150 and 300 mg/kg, was evaluated on carrageenan-induced oedema in rats to determine the most active fraction. Indomethacin, inhibitor of cyclo-oxygenase was used as reference drug. The effects of the most active fraction were then examined on the rat paw oedema caused by histamine, serotonin, arachidonic acid and dextran followed by its ulcerogenic effect. The results showed that the methylene chloride fraction of Allanblackia monticola was more effective on the oedema caused by the carrageenan. The anti-nociceptive activity of the methylene chloride fraction was assessed using the acetic acid-induced abdominal constriction model, formalin test and hot plate test. At 150 mg/kg, Allanblackia monticola caused maximum inhibitions of inflammation induced by carrageenan (83.33%), by histamine (42.10%), by dextran (40.29%) and by arachidonic acid (64.28%). Allanblackia monticola (75-300 mg/kg) did not cause significant modification of the oedema induced by serotonin. Concerning the anti-nociceptive properties of the plant, the methylene chloride fraction (75-300 mg/kg) caused a dose-dependent inhibition on abdominal contractions induced by acetic acid (32.34-77.37%) and significantly inhibited the inflammatory pain caused by formalin (40.71-64.78%). Allanblackia monticola did not increase the latency time in the hot plate test. Like indomethacin (10mg/kg), the fraction at the dose of 150 mg/kg caused ulceration of the gastric mucous membrane in treated rats. These results show that Allanblackia monticola has an anti-inflammatory and analgesic activities with gastric ulcerative side effects.

Screening of some medicinal plants from cameroon for beta-lactamase inhibitory activity.

In efforts to find new bioactive beta-lactamase inhibitors, this study investigated 16 Cameroonian plants belonging to 10 families which were evaluated for anti-beta-lactamase activity. The investigation showed that extracts 2, 6, 3 and 5 of the 16 plants investigated presented interesting in vitro beta-lactamase inhibition (over 90%), respectively, of the beta-lactamases TEM-1, OXA-10, IMP-1 and P99. These extracts were from Mammea africana (all beta-lactamases), Garcinia lucida, G. kola (OXA-10, IMP-1 and P99), Bridelia micrantha (OXA-10, P99), Ochna afzelii (OXA-10, P99), Prunus africana (IMP-1) and Adenia lobata (TEM-1). After elimination of tannins (according to the European Pharmacopoeia) the extracts from B. micrantha, G. lucida and M. africana were tested further for their anti-beta-lactamase activity. The extracts from B. micrantha and G. lucida exhibited potent inhibitory activity, respectively, of beta-lactamase OXA-10 (IC(50) = 0.02 mg/mL) and P99 (IC(50) = 0.01 mg/mL). The anti-beta-lactamase activity of M. africana extract was weak. The isolation and the structural elucidation of the active constituents of G. lucida and B. micrantha will provide useful leads in the development of beta-lactamase inhibitors.

Antimicrobial activity of the methanolic extracts and compounds from Vismia laurentii De Wild (Guttiferae).

Methanolic extracts prepared from the leaves, twigs and the roots of Vismia laurentii De Wild as well as nine compounds isolated from these crude extracts, were tested for their antimicrobial activity against Gram-positive bacteria (six species), Gram-negative bacteria (12 species) and two Candida species using disc diffusion and well micro-dilution methods. The disc diffusion assay indicated that the crude extract was active against all the pathogens tested, whereas isolated compounds showed selective activities. The degree of sensitivity of the test organisms to purified compounds varied from 25 to 90%. Fridelin (8) was found to be the most active compound, while Bivismiaquinone (3) was the least active. The lowest minimum inhibition concentration (MIC) values as obtained by the micro-dilution assays were 19.53 and 1.22 microg/ml for the crude extracts and purified compounds, respectively. The lowest value for the purified compounds (1.22 microg/ml) was obtained with O(1)-demethyl-3',4'-deoxypsorospermin-3',4'-diol (6) on Candida gabrata and Bacillus subtilis; 1,8-dihydroxy-6-methoxy-3-methylanthraquinone (5) on Bacillus subtilis and 6-deoxyisojacareubin (7) on Bacillus stearothermophilus. These results provide promising baseline information for the potential use of these crude extracts as well as some of the isolated compounds in the treatment of bacterial and fungal infections.

Alkaloids from the stem bark of Turraeanthus africanus (Meliaceae).

Fractionation of the methanol extract of the stem bark of Turraeanthus africanus led to the isolation of two new alkaloids designated turraeanthin A and B, together with two known alkaloids. The structures of the new alkaloids were elucidated by means of spectroscopic analysis and characterized as 10-O-demethyl-17-O-methyl isoarnottianamide and 11-demethoxyl-12-methoxyl oxynitidine respectively.

Laurentixanthones A and B, antimicrobial xanthones from Vismia laurentii.

A phytochemical investigation of the constituents of the roots of Vismia laurentii has resulted in the isolation of two xanthone derivatives named laurentixanthone A (1) (6-hydroxy-3,3-dimethyl-11-(3-methylbut-2-enyl)pyrano[2,3-c]xanthen-7(3H)-one) and laurentixanthone B (2) (1-hydroxy-5,6,7,8-tetramethoxyxanthone), along with 11 known compounds: 1,7-dihydroxyxanthone, vismiaquinone, vismiaquinone B, bivismiaquinone, 3-geranyloxy-6-methyl-1,8-dihydroxyanthraquinone, O(1)-demethyl-3',4'-deoxypsorospermin-3',4'-diol, 6-deoxyisojacareubin, 1,8-dihydroxy-6-methoxy-3-methylanthraquinone, kaempferol, friedelin and stigmasterol. The structures of compounds were established by means of spectroscopic methods. Furthermore, the compounds were screened for antimicrobial activities in vitro.