Antimicrobial diterpenes from the stem bark of Mitrephora celebica.

Four diterpenes were isolated from the stem bark of Mitrephora celebica through bioassay-guided fractionation. Ent-trachyloban-19-oic acid (1) and ent-kaur-16-en-19-oic acid (2) were identified as the compounds responsible for the antimicrobial activity of the plant against methicillin-resistant Staphylococcus aureus and Mycobacterium smegmatis. 8(14),15-pimaradien-18-oic acid (3) and 7,15-pimaradien-18-oic acid (4) were isolated from the same fraction and were inactive against the microorganisms.

Polyacetylene carboxylic acids from Mitrephora celebica.

A new polyacetylene carboxylic acid, 13(E),17-octadecadiene-9,11-diynoic acid (13,14-dihydrooropheic acid, 1), and the known 17-octadecene-9,11,13-triynoic acid (oropheic acid, 2) were isolated from the stem bark of Mitrephora celebica through bioassay-guided fractionation. Both compounds demonstrated significant activity against methicillin-resistant Staphylococcus aureus and Mycobacterium smegmatis.

Three new pseudodistomins, piperidine alkaloids from the ascidian Pseudodistoma megalarva.

Bioassay-guided fractionation of the MeOH-CH2Cl2 extract of the Micronesian ascidian Pseudodistoma megalarva yielded three new piperidine alkaloids, pseudodistomins D-F (3-5) and the previously reported pseudodistomins B and C (1 and 2). The structure and stereochemistry of these compounds were established by interpretation of spectral data. Pseudodistomins B-F were found to be active in a cell-based assay for DNA damage induction, but the activity was due to an alternative mechanism.

Two new nitrogenous sesquiterpenes from the sponge Axinyssa aplysinoides.

Bioassay-guided fractionation of the EtOAc extract of the Palauan sponge Axinyssa aplysinoides yielded two novel alkaloids, 1 and 2. The structure of 2-(formylamino)trachyopsane (1) was determined by X-ray analysis; and the structure of N-phenethyl-N'-2-trachyopsanylurea (2), by interpretation of the spectral data.

Daleformis, a new phytoalexin from the roots fo Dalea filiciformis: an inhibitor of endothelin converting enzyme.

As part of a search for novel inhibitors of endothelin converting enzyme (ECE), the MeOH-CH2Cl2 extract of the roots of Dalea filiciformis was shown to be active. Bioassay-guided fractionation of the extract yielded a novel phytoalexin, daleformis (1), whose structure was determined by interpretation of spectral data and X-ray analysis. Daleformis (1) inhibited ECE with an IC50 of 9 microM.

Rigidone, a sesquiterpene o-quinone from the gorgonian Pseudopterogorgia rigida.

As part of a search for novel biologically active compounds in the Macrophage Scavenger Receptor (MSR) assay, the EtOAc extract of a gorgonian coral, Pseudopterogorgia rigida, was shown to be active. Bioassay-guided fractionation of the extract yielded curcuphenol, curcuhydroquinone, curcuquinone, and a novel o-quinone, rigidone (1). The structure and stereochemistry of 1 was determined by interpretation of spectral data and chemical transformation.

Halistanol disulfate B, a novel sulfated sterol from the sponge Pachastrella sp.: inhibitor of endothelin converting enzyme.

As part of a search for novel inhibitors of endothelin converting enzyme (ECE), the MeOH extract of a South African sponge, Pachastrella sp., was shown to be active. Bioassay-guided fractionation of the extract yielded a novel sterol sulfate, halistanol disulfate B (1). The structure and stereochemistry of 1 was established mainly by interpretation of spectral data. Disulfate (1) was found to be active at a micromolar concentration in the ECE assay.

Plakortides, novel cyclic peroxides from the sponge Plakortis halichondrioides: activators of cardiac SR-CA(2+)-pumping ATPase.

As part of a search for novel activators of Ca2+ pumping activity of cardiac SR- (sarcoplasmic reticulum), the EtOAc extract of the Jamaican sponge Plakortis halichondrioides was shown to be active. Bioassay-guided fractionation of the extract followed by preparative TLC and HPLC yielded several known and novel compounds. Three of the novel cyclic peroxides, plakortides F, G, and H (3, 4, and 5) are the subject of this report. Their structures including relative stereochemistry were established by interpretation of spectral data. Micromolar concentrations of plakortides F-H (3-5) were found to significantly enhance Ca2+ uptake by SR.

Protein kinase C inhibitors: novel spirosesquiterpene aldehydes from a marine sponge Aka (= Siphonodictyon) coralliphagum.

Two novel spirosesquiterpene aldehydes, corallidictyals A [1] and B [2], were isolated as a mixture from the marine sponge Aka (= Siphonodictyon) coralliphagum, and their structures were determined by detailed spectroscopic methods. These compounds were identified in a screen for inhibitors of protein kinase C.

The inophyllums, novel inhibitors of HIV-1 reverse transcriptase isolated from the Malaysian tree, Calophyllum inophyllum Linn.

As part of a search for novel inhibitors of HIV-1 reverse transcriptase, the acetone extract of the giant African snail, Achatina fulica, was shown to be active. Fractionation of the extract yielded inophyllums A, B, C, and E and calophyllolide (1a, 2a, 3a, 3b, and 6), previously isolated from Calophyllum inophyllum Linn., a known source of nutrition for A. fulica. From a methanol/methylene chloride extract of C. inophyllum, the same natural products in considerably greater yield were isolated in addition to a novel enantiomer of soulattrolide (4), inophyllum P (2b), and two other novel compounds, inophyllums G-1 (7) and G-2 (8). The absolute stereochemistry of inophyllum A (1a) was determined to be 10(R), 11(S), 12(S) from a single-crystal X-ray analysis of its 4-bromobenzoate derivative, and the relative stereochemistries of the other inophyllums isolated from C. inophyllum were established by a comparison of their 1H NMR NOE values and coupling constants to those of inophyllum A (1a). Inophyllums B and P (2a and 2b) inhibited HIV reverse transcriptase with IC50 values of 38 and 130 nM, respectively, and both were active against HIV-1 in cell culture (IC50 of 1.4 and 1.6 microM). Closely related inophyllums A, C, D, and E, including calophyllic acids, were significantly less active or totally inactive, indicating certain structural requirements in the chromanol ring. Altogether, 11 compounds of the inophyllum class were isolated from C. inophyllum and are described together with the SAR of these novel anti-HIV compounds.

New leukotriene B4 receptor antagonist: leucettamine A and related imidazole alkaloids from the marine sponge Leucetta microraphis.

Three new imidazole alkaloids, leucettamines A [1] and B [2] and leucettamidine [3], have been isolated from the Palauan sponge Leucetta microraphis. Their structures were established on the basis of extensive spectral analyses. Leucettamine A showed potent leukotriene B4 receptor binding activity (K(i) = 1.3 microM), while leucettamine B was essentially inactive (K(i) = 100 microM) and leucettamidine showed significant activity (K(i) = 5.3 microM). With leucettamine A identified as a pure LTB4 receptor antagonist, a new structure lead is presented to inflammation therapy.

Transformation of Metalaxyl by the Fungus Syncephalastrum racemosum.

The fungus Syncephalastrum racemosum (Cohn) Schroeter was found to transform the fungicide metalaxyl [N-(2,6-dimethylphenyl)-N-(methoxyacetyl)-alanine methyl ester] in pure culture. After 21 days of incubation in a basal medium amended with 5 mug of metalaxyl per ml, more than 80% of the compound was transformed by the fungus. The transformation rates decreased as the concentrations of metalaxyl increased from 5 to 100 mug/ml. No transformation was observed when the concentration of metalaxyl was higher than 200 mug/ml. Two isomeric metabolites and a mixture of two other isomeric metabolites were isolated from the organic extract of the growth medium and identified as N-(2-methyl-6-hydroxymethylphenyl)-N- and N-(2-hydroxymethyl-6-methylphenyl)-N-(methoxyacetyl)-alanine methyl ester and N-(3-hydroxy- and N-(5-hydroxy-2,6-dimethyl-phenyl)-N-(methoxyacetyl)-alanine methyl ester according to their mass-spectral and nuclear magnetic resonance-spectral characteristics. Benzylic hydroxylation of the methyl side chains and/or aromatic hydroxylation appeared to be the major reactions involved in the metabolism of metalaxyl.