Biomedical subjects
Publications and source records attributed to K Hostettmann.
A flavones has been isolated from the roots of Polygala stenopetala. The structure was established on the basis of UV, Mass spectrum, 1HNMR, 13CHMR and NOE difference experiments as 5,7,4-trihydroxy-3, 5-dimethoxyflavone (tricin) This is for the first time that a flavones has been isolated from the species belonging to the family Polygalaceae.
From the root bark of Dictamnus dasycarpus (Rutaceae), four limonoid derivatives, two furoquinoline alkaloids, five limonoids, two sesquiterpenes and three steroids were isolated and their structures elucidated on the basis of various spectroscopic methods. Among the identified compounds, one was determined to be a new natural product, 6 beta-hydroxyfraxinellone, while six compounds were found to be active against the plant pathogenic fungus Cladosporium cucumerinum. The relationship between the structures of limonoid derivatives and their inhibitory activity against fungal growth was investigated.
Three new meroterpenoid naphthoquinones, the known cordiaquinone B and a new naphthoxirene have been isolated from the roots of Cordia linnaei. Their structures were established by spectrometric methods including EI, D/CI and FAB mass spectrometry, 1H, 13C and 2D NMR experiments. The naphthoquinones showed activity against Cladosporium cucumerinum, Candida albicans and the larvae of the yellow fever-transmitting mosquito Aedes aegypti, while the naphthoxirene derivative was found to be inactive in the same bioassays.
The CH2Cl2 extract of the leaves of Orophea enneandra displayed antifungal, antioxidant, and radical scavenging properties in bioautographic TLC assays. To obtain rapid information on the active compounds, on-flow LC/1H NMR and LC/UV/MS analyses of the antioxidant fraction were performed. The on-line information led rapidly to the partial identification of three closely related lignans, one tocopherol derivative, and one polyacetylene. This approach necessitated, however, large quantities to be injected to obtain satisfactory on-flow LC/1H NMR spectra, and isolation of the compounds was necessary to obtain complete NMR data. These compounds were isolated and identified as (-)-phylligenin (1), (-)-eudesmin (2), (-)-epieudesmin (3), polycerasoidol (4), and oropheic acid (5), a new polyacetylene. Their activities against the 2, 2-diphenyl-1-picrylhydrazyl radical and the fungus Cladosporium cucumerinum were investigated. This paper indicates the possibilities and limits of on-flow LC/1H NMR in this type of study.
Seven coumarins were isolated from the aerial parts of Tordylium apulum; their structures were established by spectroscopic means. All compounds were tested in vitro for their cytotoxicity against two cell line systems. The antiproliferative effects for three of them were studied at the level of the cell cycle in asynchronous cells of the NSCLC-N6 line with a flow cytometry apparatus.
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Three phenylpropanoid glycosides have been isolated from the methanol extract of Newbouldia laevis roots. One compound is new; its structure has been established by spectroscopic (UV, IR, FAB-MS, 1H and 13C NMR) and chemical methods as 2-(3,4-dihydroxyphenyl)ethyl-O-beta-D-apiofuranosyl-(1-->2)-O-alph a-L- rhamnopyranosyl-(1-->3)-6-O-E-feruloyl-beta-D-glucopyranoside.
Two novel triterpenoid saponins, named mussaendosides U and V, together with one known saponin and four known triterpenes were isolated from the aerial parts of Mussaenda pubescens (Rubiaceae). The structures were determined on the basis of chemical analysis ad spectral methods. All these compounds were identified for the first time from the genus Mussaenda.
Three new saponins, zanhasaponins, A, B, and C, were isolated from the MeOH extract of the root bark of Zanha africana and were, respectively, identified by spectroscopic methods as 3-O-beta-D-glucuronopyranosyl-2 beta,16 alpha-dihydroxyolean-12-ene-23,28- dioic acid 28-O-alpha-L-rhamnopyranosyl(1-->2)-alpha-L-rhamnopyranoside (1); 3-O-beta-D-glucuronopyranosyl-2 beta,16 alpha-dihydroxyolean-12-ene- 23,28-dioic acid 28-O-beta-D-xylopyranosyl(1-->2)-alpha-L-rhamnopyranosyl(1-->2)-alpha-L- rhamnopyranoside (2); and 3-O-beta-D-glucuronopyranosyl-2 beta,16 alpha-dihydroxyolean-12-ene- 23,28-dioic acid 28-O-beta-D-xylopyranosyl(1-->3)-beta-D-xylopyranosyl (1-->2)-alpha-L-rhamnopyranosyl(1-->2)-alpha-L-rhamnopyranoside (3). These saponins proved to be effective in a model of topical inflammation induced by phorbol ester. The cyclitols quebrachitol, pinitol, and bornesitol were also identified.
A MeOH extract from Z. africana was examined for topical antiinflammatory activity and proved to be active against arachidonic acid (AA) acute edema, 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced chronic inflammation, and oxazolone delayed-type hypersensitivity in mice. The extract also showed significant inhibitory activity of Naja naja phospholipase A2 when a polarographic method was used. Two oleanane-type triterpene saponins, zanhasaponins A (1) and B (2), and the cyclitol pinitol (4), isolated from the extract, were active as inhibitors of PLA2. A further saponin, zanhasaponin C (3) was inactive in this assay.
Species of the genus Epilobium (Onagraceae) have been investigated for their activity against 5 alpha-reductase and aromatase, two enzymes which are involved in the aetiology of benign prostatic hyperplasia (BPH). Activity-guided fractionation has led to the identification of two macrocyclic ellagitannins, oenothein A (1) and oenothein B (2), as the main constituents responsible for the inhibition of the two enzymes. Quantitation of oenothein B in 10 different species of Epilobium has shown that amounts of up to 14% in the crude plant extracts are possible.
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Fractionation of an aqueous acetone extract of the whole herb of Gentiana algida gave one new [2'-(o,m-dihydroxybenzyl)sweroside] and five known secoiridoids, together with anofinic acid, fomannoxin acid, sitosterol, daucosterol, stigmasterol, oleanolic acid, orientin and gentianose. The structures were determined by spectral methods and a few chemical transformations. Anofinic acid and fomannoxin acid were found to be active against Cladosporium cucumerinum, a plant pathogenic fungus. Preliminary structure-activity studies indicated that the presence of carboxylic moieties in these acids was presumably a precondition for activity, whereas their methyl esters, inactive to the fungus, were active against the human pathogenic yeast Candida albicans. The chemotaxonomic significance of the isolates is discussed briefly.
Phytochemical examination of the dichloromethane extract of the European fungus Fomitopsis pinicola led to the isolation of a new lanostanoid derivative identified from spectral and chemical evidences as 3 alpha-(4-carboxymethyl-3-hydroxy-3-methylbutanoyloxy)-lanosta++ +-8,24-dien-21-oic acid. In addition, seven known triterpenes, polyporenic acid C, 3 alpha-acetyloxylanosta-8,24-dien-21-oic acid, ergosta-7,22-dien-3 beta-ol,21-hydroxylanosta-8,24-dien-3-one, pinicolic acid A, trametenolic acid B and pachymic acid, were also isolated. Antimicrobial activity against Bacillus subtilis in a TLC bioassay was observed for five of the isolated steroids.
From a dichloromethane extract of Newbouldia laevis roots, four new (6-hydroxydehydroiso-alpha-lapachone, 7-hydroxydehydroiso-alpha-lapachone, 5,7-dihydroxydehydroiso-alpha-lapachone and 3-hydroxy-5-methoxydehydroiso-alpha-lapachone) and six known naphthoquinones have been isolated. Their structures were established by spectroscopic methods (UV, EI mass spectrometry, 1H and 13C NMR) and that of 7-hydroxydehydroiso-alpha-lapachone was confirmed by X-ray crystallography. All naphthoquinones showed antifungal activity against Cladosporium cucumerinum and Candida albicans, and activity against the bacteria Bacillus subtilis and Escherichia coli.
LC-UV-mass spectrometry and bioassay co-directed fractionation of an aqueous acetone extract of the roots of Gentiana macrophylla gave three new chromene derivatives and two novel and six known secoiridoids, along with kurarinone, kushenol I, beta-sitosterol, stigmasterol, daucosterol, beta-sitosterol-3-O-gentiobioside, alpha-amyrin, oleanolic acid, isovitexin, gentiobiose and methyl 2-hydroxy-3-(1-beta-D-glucopyranosyl)oxybenzoate. The structures of the new products were established from spectral and chemical evidence as 2-methoxyanofinic acid and macrophyllosides A-D. The six known secoiridoids were gentiopicroside, sweroside, 6'-O-beta-D-glucosylgentiopicroside, 6'-O-beta-D-glucosylsweroside, trifloroside and rindoside. The new acid (2-methoxyanofinic acid), its methyl ester, kurarinone and kushenol I were shown to be active against the plant pathogenic fungus Cladosporium cucumerinum. The methyl ester and kurarinone inhibited also the growth of the human pathogenic yeast Candida albicans. Structure-activity relationships were studied. Thus, addition of a methoxyl group to the benzene nucleus of anofinic acid (2,2-dimethyl-2H-1-benzopyran-6-carboxylic acid) increased the antifungal activity remarkably whereas glycosylation at the carboxylic moiety was found to remove the activity. Esterification of the new acid induced its activity against C. albicans, but decreased its growth inhibition properties against C. cucumerinum. Hydroxylation of kurarinone at the 3 beta-position removed its activity against C. albicans and decreased the inhibition of C. cucumerinum. In addition, the chemotaxonomic significance of the identified constituents is discussed.
Four new xanthones have been isolated from the roots of Hypericum roeperanum. Their structures have been established by a combination of spectroscopic and chemical methods as 1,6-dihydroxy-5-methoxy-4',5'-dihydro-4',4',5'-trimethylfurano- (2',3':3,4)-xanthone (5-O-methyl-2-deprenylrheediaxanthone B), 1,6-dihydroxy-5-methoxy-6',6'-dimethylpyrano-(2',3':3,4)-xanthone (5-O-methylisojacareubin), 1,3,5,6-tetrahydroxy-2-(2',2'-dimethyl-4'-isopropenyl)-cyclopen tanylxanthone (5-O-demethylpaxanthonin) and 1,3,5,6-tetrahydroxy-4-trans-sesquilavandulylxanthone (roeperanone). In addition, 2-hydroxyxanthone, 5-hydroxy-2-methoxyxanthone, 1,5-dihydroxy-2-methoxyxanthone, 2-deprenyl rheediaxanthone B, isojacareubin and calycinoxanthone D have been isolated and characterized. Some of the isolated xanthones exhibited antifungal activity against Candida albicans.
The dichloromethane extract of the leaves of Myrica serrata inhibits growth of Cladosporium cucumerinum, Bacillus subtilis, and Escherichia coli on TLC plates. Activity-guided fractionation led the isolation of 2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone (1), 2',4'-dihydroxy-6'-methoxy-5'-methylchalcone (aurentiacin A) (2), 2',6'-dihydroxy-4'-methoxy-3',5'-dimethyldihydrochalcone (3), 2'-hydroxy-4',6'-dimethoxy-3'-methyldihydrochalcone (4), and 2', 6'-dihydroxy-4'-methoxy-3'-methyldihydrochalcone (5). In addition, the flavanones demethoxymatteucinol (6) and cryptostrobin (7) were also identified.