Antimalarial and vasorelaxant constituents of the leaves ofAllanblackia monticola(Guttiferae)

Phytochemical investigation of the leaves of Allanblackia monticola led to the isolation and characterisation of five prenylated xanthones [1,6-dihydroxy-3,7-dimethoxy-2-(3-methylbut-2-enyl)xanthone 1, alpha-mangostin 2, tovophyllin A 3, allanxanthone C 4 and 1,7-dihydroxy-3-methoxy-2-(3-methylbut-2-enyl)xanthone 5], two biflavonoid derivatives (amentoflavone 6 and podocarpusflavone A 7) and one pentacyclic triterpene (friedelan-3-one 8). The structures of these compounds were established on the basis of homo- and hetero-nuclear, one- and two-dimensional, nuclear magnetic resonance. Compounds 2-8 and a crude methanolic extract of A. monticola leaves were each tested for antimalarial activity in vitro, using the chloroquine-sensitive F32 and chloroquine-resistant FcM29 strains of Plasmodium falciparum; the median inhibitory concentrations (IC(50)) recorded varied from 0.7 to 83.5 mug/ml. The cytotoxicities of the compounds and crude extract, against cultures of human melanoma cells (A375), were then investigated, and cytotoxicity/antimalarial IC(50) ratios of 0.6-16.75 were recorded. In tests involving aortic rings from guinea pigs, a crude extract of the leaves of A. monticola was found to induce concentration-dependent vasorelaxation, causing up to 82% and 42% inhibition of noradrenaline- and KCl-induced contractions, respectively. The corresponding values for compounds 2 and 6 when tested against noradrenaline-induced contractions were approximately 18% and 35%, respectively.

Cytotoxic and antimicrobial coumarins fromMammea africana

Six coumarin derivatives [three 4-phenylcoumarins (Mammea A/AA, Mammea A/BA and MAB 3), two 4-n-propylcoumarins (Mammea B/BB and Mammea B/BA) and one 4-n-pentylcoumarin (Mammea C/OB)], 1,5-dihydroxyxanthone and 1-methoxy-5-hydroxyxanthone have been isolated from the stem bark of Mammea africana Sabine collected in Cameroon. Although known, the structures of the coumarin derivatives were confirmed by spectral analysis, including two-dimensional nuclear magnetic resonance. All the coumarin compounds showed noteworthy cytotoxicity against the human 9-KB cell line. Both of the 4-n-propylcoumarins were also found to exhibit significant activity against Staphylococcus aureus.

Apoptotic effects on B-cell chronic lymphocytic leukemia (B-CLL) cells of heterocyclic compounds isolated from Guttiferaes

A series of 10 heterocyclic compounds purified from Allanblackia were tested on two B cell lines, ESKOL and EHEB, and on cells from B-CLL patients. Several molecules inhibited the proliferation of both cell lines and promoted apoptosis of B-CLL cells through different mechanisms, some of them elicited a dissipation of the mitochondrial transmembrane potential, other triggered caspase-3 activation and cleavage of the inducible nitric oxide synthase. Blood mononuclear cells and B-lymphocytes from healthy donors appeared less sensitive than B-CLL cells. These results indicate that these molecules may be of interest in the development of new therapies for B-CLL.

Antimicrobial activity of the methanolic extract and of the chemical constituents isolated from Newbouldia laevis

The methanolic extract (NLB) and ten compounds isolated from the root bark of Newbouldia laevis Seem, namely chrysoeriol (1), newbouldiaquinone (2), 2-acetylfuro-1,4-naphthoquinone (3), 2-hydroxy-3-methoxy-9,10-dioxo-9,10-dihydroanthracene-1-carbaldehyde (4), lapachol (5), beta-sitosterol-3-O-beta-D-glucopyranoside (6), oleanolic acid (7), canthic acid (8) newbouldiamide (9) and 2-(4-hydroxyphenyl)-ethyltrioctanoate (10), were tested for in vitro antimicrobial activity. Twenty one microorganisms belonging to six Gram-positive and twelve Gram-negative bacterial species as well as three yeasts from Candida species were tested for their susceptibility to NLB and the pure isolated compounds based on the Agar Hole Diffusion test and the Liquid Dilution method. The Hole Diffusion assay indicated that NLB and compound 7 were active against all tested pathogens while other compounds showed selective activity with the antimicrobial spectra varying from 76% (compound 10) to 95 % (compound 6). Minimal inhibitory concentrations (MIC) also illustrated the important antimicrobial activity of NLB and of the isolated compounds. MIC values obtained varied from 9.76 to 312.50 microg/ml for NLB, and 0.038 to 9.76 microg/ml for pure compounds against most of the tested microorganisms. The antimicrobial activities of compounds 2, 4 and 9 are described here extensively for the first time. The results indicate a promising basis for the use of Newbouldia laevis and some of its active principles in the treatment of infectious diseases.

Vasodilator effect of the extracts and some coumarins from the stem bark of Mammea africana (Guttiferae)

CH(2)Cl(2) fraction obtained from the stem bark of Mammea africana inhibited noradrenaline (NA) or KCl-induced contraction in isolated guinea pig and rat aorta. The vasorelaxant potency of the CH(2)Cl(2) fraction of Mammea africana was diminished by a pre-treatment with Nitro-L-arginine methyl ester (L-NAME), an inhibitor of NO synthase, which was however not affected by indomethacin pre-treatment. These findings indicated that the vasorelaxant effect of Mammea africana may be partially endothelium dependent, mediated by nitric oxide and that vasoactive prostanoids might not be contributing to the vasorelaxation effect. Three bioactive compounds were isolated from this CH(2)Cl(2) fraction and identified as 4-n-propylcoumarins (1) (mammea B/BB), 4-phenylcoumarins (2) (mammea A/AA or mammeisin) and (B/BA) (3) and might involved in the vasorelaxant effect of the extract. The mechanisms of the vasorelaxant effect might therefore be multiple, including endothelium dependence and the mechanisms, which interfere with the liberation of Ca(2+) into the muscle cell.

Securidacaxanthone A, a heptaoxygenated xanthone from Securidaca longepedunculata

From the root bark of Securidaca longepedunculata, a heptaoxygenated xanthone (1) has been isolated as well as two known xanthones (2) and (3) and two salicylic acid derivatives (4) and (5). The structure of 1 has been elucidated from 1H and 13C-NMR spectral data.

Newbouldiaquinone A: A naphthoquinone-anthraquinone ether coupled pigment, as a potential antimicrobial and antimalarial agent from Newbouldia laevis

The study of the chemical constituents of the roots of Newbouldia laevis (Bignoniaceae) has resulted in the isolation and characterization of a naphthoquinone-anthraquinone coupled pigment named newbouldiaquinone A (1) together with 14 known compounds: apigenin, chrysoeriol, newbouldiaquinone, lapachol, 2-methylanthraquinone, 2-acetylfuro-1,4-naphthoquinone, 2,3-dimethoxy-1,4-benzoquinone, oleanolic acid, canthic acid, 2-(4-hydroxyphenyl)ethyl triacontanoate, newbouldiamide, 5,7-dihydroxydehydroiso-alpha-lapachone, beta-sitosterol, and beta-sitosterol glucopyranoside. The structure elucidation of the isolated compounds was established based on spectroscopic studies, notably of the 2D NMR spectra. The antimalarial activity of compound (1) against Plasmodium falciparum in vitro shows moderate chemo suppression of parasitic growth. Its antimicrobial activity against a wide range of microorganisms was 13- and 24-fold more active against Candida gabrata and Enterobacter aerogens than the reference antibiotics nystatin and gentamycin.

Newbouldiaquinone and Newbouldiamide: A New Naphthoquinone-Anthraquinone Coupled Pigment and a New Ceramide from Newbouldia laevis

Newbouldiaquinone (1), a new naphthoquinone-anthraquinone coupled pigment and a new ceramide named newbouldiamide (2), have been isolated from Newbouldia laevis, besides the known compounds lapachol (3), canthic acid, oleanolic acid, 2-methyl-9,10-anthracenedione, 2-acetylfuro-1,4-naphthoquinone, 2,3-dimethoxy-1,4-benzoquinone, 2-(4-hydroxyphenyl)ethyl triacontanoate, beta-sitosterol and beta-sitosterol glucopyranoside. The structure elucidations of the isolated new compounds were performed on the basis of spectroscopic and chemical evidence. Preliminary studies showed that 1 is moderately antibacterial against Gram-positive Bacillus megaterium and that 3 has moderate herbicidal and antibacterial activities.

In-vivo antimalarial activity of some oxygenated xanthones

A series of oxygenated xanthones was prepared so that the antimalarial activity of each compound could be evaluated in vivo, using 4-day suppressive assays against Plasmodium berghei ANKA in BALB/c mice. When given in a dose of 20 mg/kg.day for 4 days, most of the compounds produced significant chemosuppression of parasitaemia. The most active compound was 1,3,6,8-tetrahydroxyxanthone, which reduced the percentage of erythrocytes infected by 70.5%, followed by norlichexanthone (44.3%) and its isomer, 1,3,8-trihydroxy-6-methylxanthone (37.0%). Whereas di-C-allyl-dihydroxyxanthone showed lower but still notable activity (33.4%), 1,3-dihydroxyxanthone was much less active (15.1%). This appears to be the first demonstration of the antimalarial activity of some hydroxyxanthones in vivo.

Scaphopetalone and scaphopetalumate, a lignan and a triterpene ester from Scaphopetalum thonneri

From the methanol extract of the stem bark of Scaphopetalum thonneri, two new compounds, including one lignan, named scaphopetalone, one new ester of ferulic acid, named scaphopetalumate were isolated together with three known compounds including: two coumarins (scopoletin and scopolin), and one pentacyclic triterpene (oleanolic acid). The structure of the new compounds were elucidated by means of spectroscopic analyses.

Cytotoxic isoflavones from Erythrina indica

Bioassay-directed fractionation of the CH(2)Cl(2)-MeOH (1:1) extract of the stem bark of Erythrina indica, has resulted in the isolation of two new isoflavone derivatives named indicanines D and E together with 11 known compounds including: six isoflavones (genistein, wighteone, alpinumisoflavone, dimethylalpinumisoflavone, 8-prenyl erythrinin C, and erysenegalensein E), one cinnamate (erythrinassinate B), two pentacyclic triterpenes (oleanolic acid and erythrodiol), and two phytosterols (stigmasterol and its 3-O-beta-D-glucopyranoside). The structures of the new compounds were elucidated by means of spectroscopic analysis. The in vitro cytocidal activity against KB cells of some of the isolated compounds is also reported.

Asebotin, a dihydrochalcone glucoside from Guibourtia tessmannii

Asebotin (1), a dihydrochalcone glucoside, was isolated from the stem bark of Guibourtia tessmanni and characterised by means of spectroscopic analysis including 1H-, 13C, MS and 1D Noe difference experiment.

Diterpenoid and limonoids from the stem of Pterorhachis zenkeri

One new diterpenoid, methyl 3alpha-hydroxy-7-oxo-dehydroabietate (1), two new limonoids, 3alpha-deacetyl-amoorastatin (2) and 9beta-amoorastatin (3), and the known limonoid amoorastatin (4) were isolated from the stem of Pterorhachis zenkeri.

Indicanine A, a new 3-phenylcoumarin from root bark of Erythrina indica

A new 3-phenylcoumarin, indicanine A (1), has been isolated from the root bark of the African medicinal plant Erythrina indica, together with three known compounds, robustic acid (2), daidzein, and 8-prenyldaidzein. The structure of the new compound was characterized, as 4-hydroxy-5-methoxy-3-(4'-methoxyphenyl)-2" -(1-methylethenyl)dihydrofurano[4",5":6,7]coumarin by means of extensive spectroscopic analyses. The compounds were found to be devoid of in vitro antibacterial activity.

Indicanines B and C, two isoflavonoid derivatives from the root bark of Erythrina indica

In addition to two known compounds, 5,4'-di-O-methylalpinumisoflavone and cajanin, a new 3-phenylcoumarin metabolite, named indicanine B, and a new isoflavone derivative, named indicanine C, were isolated from the root bark of Erythrina indica. By means of spectroscopic analysis, the structures of the new compounds were characterized as 4-hydroxy-3-(4'-hydroxyphenyl)-5-methoxy-2",2"-dimethylpyrano [5",6":6,7] coumarin and 4'-hydroxy-5-methoxy-2",2"-dimethylpyrano [5",6":6,7] isoflavone, respectively. The 13C-NMR data of cajanin and the in vitro antimicrobial spectrum and potencies of the isolated compounds are also reported.

Conrauinones A and B, Two New Isoflavones from Stem Bark of Millettia conraui1

Two new isoflavones, named conrauinones A (1) and B (2), have been isolated from the stem bark of Millettia conraui, in addition to known 5-methoxydurmillone. The structures of the new compounds were determined by spectroscopic analysis including 2D NMR techniques as 5,6,2'-trimethoxy-4',5'-(methylenedioxy)-2",2"-dimethylpyrano[5",6":7,8]isoflavone (1) and 6-methoxy-3',4'-(methylenedioxy)-7-O-[(E)-3",7"-dimethyl-7"-ol-2",5"-octadienyl]isoflavone (2).

Prenylated isoflavanone from Erythrina eriotricha

Bioassay-directed fractionation of a methylene chloride extract of the root bark of Erythrina eriotricha resulted in the isolation of a novel isoflavanone, named eriotrichin B, and the five known pterocarpans, isonorautenol, erybraedin A, erybraedin C, erybraedin D and erybraedin E. The structure of the new compound has been investigated by extensive spectroscopic studies, including 2D NMR and chemical evidence. The in vitro antimicrobial spectrum and potencies of the isolated compounds are also reported.

Sigmoidins J and K, two new prenylated isoflavonoids from Erythrina sigmoidea

In addition to the two known compounds neotautenol [2] and erythrinassinate B [4], two new compounds, an isoflavanone named sigmoidin J [1] and a coumestan derivative named sigmoidin K [3], have been isolated and characterized from the root bark of the Cameroonian medicinal plant Erythrina sigmoidea. Their structures have been established as 7, 4'-dihydroxy-2',5'-dimethoxy-6'(gamma, gamma-dimethylally)isoflavanone [1] and 3,9-dihydroxy-2,10-(gamma, gamma dimethylallyl) coumestan [3], respectively, by spectroscopic techniques and from chemical evidence.

Prenylated isoflavanone from the roots of Erythrina sigmoidea

A novel prenylated isoflavanone, sigmoidin I, has been isolated from the roots of Erythrina sigmoidea, in addition to the known isoflavones, corylin and neobavaisoflavone and the known pterocarpan, phaseollidin. Its structure was established as 7,4'-dihydroxy-3'-methoxy-5'-(3-methylbut-2-enyl) isoflavanone by means of spectroscopic analyses and chemical transformations. Neobavaisoflavone displayed antifungal potency in vitro with minimum inhibitory concentrations against Aspergillus fumigatus and Cryptococcus neoformans, of 50 mg ml-1.

Auriculatin 4'-O-Glucoside: A New Prenylated Isoflavone Glycoside from Erythrina eriotricha1

In addition to known compounds, sigmoidin C and 8-(3,3-dimethylallyl)-erythrinin C, also called senegalensin, a new isoflavone glycoside designated auriculatin 4'- O-glucoside was isolated from the chloroform extract of the stem bark of ERYTHRINA ERIOTRICHA. Its structure was elucidated as 7,6-(2''',2'''-dimethyl-2 H-pyrano)-2',5-dihydroxy-8-(3,3-dimethylallyl)-isoflavone 4'- O-beta- D-glucoside on the basis of spectroscopic methods and chemical evidence.

A new prenylated isoflavone and long chain esters from two Erythrina species

Two new compounds, a long chain ester 1 of p-coumaric acid and a prenylated isoflavone, senegalensin [5], 5,4'-dihydroxy-8-(gamma,gamma-dimethylallyl)-[5"-(hydroxyisopropyl ) (2",3":6.7)] isoflavone, in addition to a known long chain ester 2 of ferulic acid, have been isolated and characterized from the stem bark of the Cameroonian medicinal plant Erythrina senegalensis. Another known compound 3, a long chain ester of ferulic acid, was isolated from Erythrina excelsa. The structures of all the compounds were determined by spectroscopic techniques.