Biomedical subjects

Ratnakar N Asolkar

Publications and source records attributed to Ratnakar N Asolkar.

8 recordsLinked to original sources

PubMed2006

Daryamides A-C, weakly cytotoxic polyketides from a marine-derived actinomycete of the genus Streptomyces strain CNQ-085.

In the course of our continuing search for new antitumor-antibiotics from marine-derived actinomycete bacteria, four new cytotoxic compounds, designated as daryamides A (1), B (2), and C (3) and (2E,4E)-7-methylocta-2,4-dienoic acid amide (4), were isolated from the culture broth of a marine-derived Streptomyces strain CNQ-085. The structures of these new compounds were assigned by detailed interpretation of spectroscopic data. The relative configuration of 1 was determined by comprehensive NMR analysis, while the absolute configuration of 1 was determined as 4S,5R using the modified Mosher method. The daryamides show weak to moderate cytotoxic activity against the human colon carcinoma cell line HCT-116 and very weak antifungal activities against Candida albicans.

Antibiotics, Antineoplastic↗

PubMed2004

An acetoxygenated analogue of ergosterol from a soft coral of the genus Lobophytum.

Chemical investigation of a soft coral of the genus Lobophytum of the Andaman and Nicobar coasts resulted in the isolation of a new marine sterol acetate, (24S)-ergostane-3beta,5alpha,6beta,25-tetraol-3,6,25-triacetate (1) and of two known sterol glycosides 3beta,4alpha-dihydroxypregn-20-ene-4-O-beta-D-arabinopyranoside and 24-methylenecholest-5-ene-3beta,7beta, 16beta-triol-3-O-alpha-L-fucopyranoside-7beta-acetate. The structures of the compounds were elucidated based on spectral studies and chemical conversions.

Animals↗

PubMed2004

Helquinoline, a new tetrahydroquinoline antibiotic from Janibacter limosus Hel 1+.

The ethyl acetate extract of cultures of Janibacter limosus showed a high biological activity against bacteria, and fungi and delivered two new natural products, a tetrahydroquinoline derivative designated as helquinoline (1), and the N-acetylkynuramine (3a), along with other known secondary metabolites. The structure of 1 has been elucidated as 4-methoxy-2-methyl-1,2,3,4-tetrahydroquinoline-8-carboxylic acid on the basis of 1D and 2D NMR and mass spectra. The relative stereochemistry of the compound 1 was assigned as 2R*,4R* with the aid of coupling constants, NOESY correlation and by comparison with a related compound.

Actinomycetales↗

PubMed2003

Seitomycin: isolation, structure elucidation and biological activity of a new angucycline antibiotic from a terrestrial Streptomycete.

A new antibiotic, named seitomycin (1c), and the known microbial metabolite tetrangulol methyl ether (2) were found in the ethyl acetate extract of two terrestrial Streptomyces sp. isolates. The structure of the new antibiotic was elucidated by spectroscopic studies and by comparison of the NMR data with the structurally related hatomarubigin C (1a) and SM-196 B (1b). Seitomycin (1c) showed moderate antimicrobial and weak phytotoxic activity, similar to tetrangulol methyl ether (2).

Anti-Bacterial Agents↗

PubMed2002

Horiolide, a novel norditerpenoid from Indian ocean soft coral of the genus Sinularia.

A novel norditerpenoid, horiolide (1), has been isolated from an Indian Ocean soft coral of the genus Sinularia. The structural elucidation was achieved by a study of its spectral characteristics. This compound is structurally characterized by a new carbon skeleton having one six-membered cyclohexane ring bearing an isopropylene moiety, a carbonyl group, and one seven-membered ring attached to a five-membered lactone moiety.

Animals↗

PubMed2002

Limnazine, the first bacterial azine derivative from Bacillus sp. GW90a.

A novel dimeric azine derivative designated as limnazine (1) has been isolated from the culture broth of an aquatic Bacillus sp. strain GW90a. The structure has been elucidated, on the basis of spectral data, as N,N'-bis(2,2,6-trimethylchroman-4-ylidene)azine and was additionally confirmed by synthesis. Limnazine (1) is inactive against algae, fungi, and bacteria.

Bacillus↗

PubMed2002

Phytotoxic arylethylamides from limnic bacteria using a screening with microalgae.

N-Phenylethylamides 1a-1f, were isolated from cultures of three limnic strains GW90a, GW102a and GW73a. Strain GW102a delivered additionally the compound cyclo(isoleucyldehydroalanyl) (2). The structure of these compounds were assigned by a detailed spectral analysis. Due to their potential use as herbicides, various related compounds 1a, 3, 4a and 4b were synthesized. The minimum inhibitory concentration (MIC) against Chlorella vulgaris, Chlorella sorokiniana, Chlorella salina and Scenedesmus subspicatus ranged from 100 to 12.5 microg/ml. All these amides were found to be inactive against Mucor miehei, Candida albicans, and some bacteria.

Amides↗

PubMed2002

Chalcomycin B, a new macrolide antibiotic from the marine isolate Streptomyces sp. B7064.

In our screening of marine streptomycete isolates for bioactive components, a new macrolide antibiotic designated as chalcomycin B (1b) was isolated from the culture broth of a marine Streptomycete isolate B7064 together with chalcomycin (1a) as the active principles. The structure of the new antibiotic was determined by EI and ESI MS, 1H, 13C and 2D NMR spectroscopy and by comparison of the NMR data with those of chalcomycin.

Anti-Bacterial Agents↗