M. Meyer

Cytotoxic and antimicrobial coumarins from Mammea africana

Abstract 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.

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.

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.

Phenolic metabolites from Erythrina species

From the stem and root bark of Erythrina sigmoidea and E. eriotricha, one new prenylated flavanone, named sigmoidin L, and two new esters of ferulic and isoferulic acid, erythrinassinates C and D, were isolated together with eight known compounds, including one ester of isoferulic acid [3β-O-(E)-isoferuloyl oleanolic acid], one flavanone (sigmoidin A), four isoflavones (scandenone, 6,8-diprenylgenistein), flemiphilippinin B and 8-prenyldaidzein and two pterocarpans (gangetinin and calopocarpin). Their structures were elucidated by analysis of spectral data and chemical evidence. The in vitro anitmicrobial spectrum and potencies of the isolated compounds are also reported.

An antiplasmodial new (bis)indole alkaloid from the hard coral Tubastraea sp.

Tubastarea sp., a stony coral (Dendrophylliidae) from the Great Hanish in the Archipelago of the Hanish Islands, Yemen, contains, in addition to the known aplysinopsin (1) and 6-bromo-3′-deimino-3′-oxoaplysinopsin (2), the new bis(indole) alkaloid (3). The structures of compounds (1–3) were elucidated by interpretation of spectral data. Compound 3 inhibits the growth of Plasmodium falciparum (chloroquine-resistant strain) with an IC50 1.2 µg mL−1.

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.

An 3-indolyl-imidazol-4-one from the tunicate Dendrodoa grossularia.

Abstract A new compound, possessing an unusual 4H-imidazole ring uas isolated; structure elucidation was performed using spectral analysis and confirmed by synthesis.

Antimicrobial and antileishmanial xanthones from the stem bark of Allanblackia gabonensis (Guttiferae)

The phytochemical study of stem bark of Allanblackia gabonensis has resulted in the isolation and characterisation of one new xanthone derivative, named allanxanthone D, together with 10 known compounds, including 6 xanthones derivatives, allanxanthone A, 1,5-dihydroxyxanthone, 1,7-dihydroxyxanthone and 1,3,6,7-tetrahydroxy-2-(3-methylbut-2-enyl)xanthone, forbexanthone, 6-deoxyisojacareubin, one polyisoprenylated benzophenone, guttiferone F, one flavanol, epicathechin, two phytosterols, beta-sitosterol and campesterol. The structures of these compounds were established on the basis of one- and two-dimensional NMR homo- and hetero-nuclear evidence. These compounds were evaluated for their activity against Leishmania amazonensis in vitro and antimicrobial activities against a range of Gram negative and Gram positive bacteria.

Synthesis of 2-substituted indolo pyridin-4-ones

Abstract The synthesis of 2-substituted indolo-pyridin-4-ones was achieved in good yields by a one-pot reaction between Nue5f8Me amino-2-indole (as hydriodide) with acetylenic esters.

ANTIMICROBIAL AND ANTILEISHMANIAL XANTHONES FROM THE STEM BARK OF Allanblackia gabonensis

The phytochemical study of the stem bark of Allanblackia gabonensis has resulted in the isolation and characterization of one new xanthone derivative, named allanxanthone D, together with ten known compounds, including six xanthone derivatives, allanxanthone A, 1,5-dihydroxyxanthone, 1,7-dihydroxyxanthone and 1,3,6,7-tetrahydroxy-2-(3-methylbut-2-enyl)xanthone, forbexanthone, 6-deoxyisojacareubin, one polyisoprenylated benzophenone, guttiferone F, one flavanol, epicathechin, two phytosterols, β-sitosterol, and campesterol. The structures of these compounds were established on the basis of one- and two-dimensional NMR homo- and heteronuclear evidence. These compounds were evaluated for their activity against Leishmania amazonensis in vitro and antimicrobial activities against a range of Gram-negative and Gram-positive bacteria.