Peddikotla Prabhakar

Purification and biological evaluation of the metabolites produced by Streptomyces sp. TK-VL_333

An Actinobacterium strain isolated from laterite soils of the Guntur region was identified as Streptomyces sp. TK-VL_333 by 16S rRNA analysis. Cultural, morphological and physiological characteristics of the strain were recorded. The secondary metabolites produced by the strain cultured on galactose-tyrosine broth were extracted and concentrated followed by defatting of the crude extract with cyclohexane to afford polar and non-polar residues. Purification of the two residues by column chromatography led to isolation of five polar and one non-polar fraction. Bioactivity- guided fractions were rechromatographed on a silica gel column to obtain four compounds, namely 1H-indole-3-carboxylic acid, 2,3-dihydroxy-5-(hydroxymethyl) benzaldehyde, 4-(4-hydroxyphenoxy) butan-2-one and acetic acid-2-hydroxy-6-(3-oxo-butyl)-phenyl ester from three active polar fractions and 8-methyl decanoic acid from one non-polar fraction. The structure of the compounds was elucidated on the basis of FT-IR, mass and NMR spectroscopy. The antimicrobial activity of the bioactive compounds produced by the strain was tested against the bacteria and fungi and expressed in terms of minimum inhibitory concentration. Antifungal activity of indole-3-carboxylic acid was further evaluated under in vitro and in vivo conditions. This is the first report of 2,3-dihydroxy-5-(hydroxymethyl) benzaldehyde, 4-(4-hydroxyphenoxy) butan-2-one, acetic acid-2-hydroxy-6-(3-oxo-butyl)-phenyl ester and 8-methyl decanoic acid from the genus Streptomyces.

Production of bioactive metabolites by Nocardia levis MK-VL_113

Aims:  To isolate and identify the bioactive compounds produced by Nocardia levis MK‐VL_113.

Isolation, characterization and biological evaluation of bioactive metabolites from Nocardia levis MK-VL_113.

An Actinomycete isolate found to be prominent in the laterite soils of Acharya Nagarjuna University (ANU) Campus, Guntur was identified as Nocardia levis MK-VL_113 by 16S rRNA analysis. Cultural, morphological and physiological characteristics of the strain were recorded. Screening of secondary metabolites obtained from 4-day old culture broth of the strain led to the isolation of two fractions active against a wide variety of Gram-positive, Gram-negative bacteria and fungi. The structure of the first active fraction was elucidated using FT-IR, EI-MS, (1)H NMR and (13)C NMR spectra and identified as 1-phenylbut-3-ene-2-ol which is first time reported as a natural product. The compound exhibited good antimicrobial potential against the opportunistic and pathogenic bacteria and fungi. The antifungal activity of the strain and its metabolite were further confirmed with in vitro and in vivo studies. Evidence for the antagonism of the strain against Fusarium oxysporum, causing wilt disease in sorghum was demonstrated by the formation of inhibition zone in in vitro plate assay and reduction in the incidence of wilt of sorghum plants by using a green house trial. Analysis of the rhizosphere soil extracts by high performance liquid chromatography also demonstrated the production of the compound by the strain under in vivo conditions. As compared to the commercial fungicide mancozeb, the bioactive compound, 1-phenylbut-3-ene-2-ol was highly effective in controlling wilt of sorghum. Besides, the partially purified second fraction (PPF) subjected to gas chromatography-mass spectrometry revealed the presence of phenylethyl alcohol, dibutyl phthalate and 1,2-benzenedicarboxylic acid, 3-nitro.

Stereoselective synthesis and biological evaluation of (R)-rugulactone, (6R)-((4R)-hydroxy-6-phenyl-hex-2-enyl)-5,6-dihydro-pyran-2-one and its 4S epimer

A simple and highly efficient synthetic route has been developed for synthesis of (R)-rugulactone (1a), (6R)-((4R)-hydroxy-6-phenyl-hex-2-enyl)-5,6-dihydro-pyran-2-one (1b) and its 4S epimer 1c by employing proline-catalyzed alpha-aminooxylation, Sharpless epoxidation, Mitsunobu reaction as chirality introuducing steps. The antibacterial and antifungal activity of the compounds 1a, 1b and 1c were evaluated. 1a and 1b showed better antibacterial activity against Pseudomonas aeroginosa (MIC=12.5 microg/ml for 1a, 25 microg/ml for 1b) Klebsiella pneumonia (MIC=25 microg/ml for 1a). Compounds (1a, 1b, 1c) exhibited good to moderate antifungal activity.

Stereoselective first total synthesis, confirmation of the absolute configuration and bioevaluation of botryolide-E.

A simple, first stereoselective total synthesis of botryolide-E has been described. The synthesis started from propylene oxide employing Jacobsens hydrolytic kinetic resolution (HKR), selective epoxide opening, sharpless asymmetric dihydroxylation, one pot acetonide deprotection and lactonization as key steps. Further, the synthesis confirms the absolute configuration of the natural product botryolide-E and we evaluated the biological behavior of natural product botryolide-E against a panel of bacteria and fungi. Botryolide-E exhibits significant potent activity against Staphylococcus aureus (MTCC 96) (6.25 μg/ml), good against Escherichia coli (MTCC 443) (12.5 μg/ml), Bacillus subtilis (MTCC 441) (25 μg/ml) and compound 1 exhibited good to moderate antifungal activity.

Facile tert‐Butoxycarbonylation of Alcohols, Phenols, and Amines using BiCl3 as a Mild and Efficient Catalyst

Abstract Facile tert‐butoxycarbonylation of alcohols, phenols, and amines is described by treatment of alcohols, phenols, and amines with di‐tert‐butyl dicarbonate in the presence of a catalytic amount of bismuth(III) chloride, a mild and efficient catalyst, at room temperature in excellent yields.