Browsing by Author "Arunima Srivastava"

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Antibacterial potential of γ-linolenic acid from Fischerella sp. colonizing Neem tree bark
(2006) Ravi K. Asthana; Arunima Srivastava; Arvind M. Kayastha; Gopal Nath; Sureshwar P. Singh
Pharmaceutically important γ-linolenic acid (GLA) was produced (4.1 mg g-1 dry wt) by laboratory grown cyanobacterium Fischerella sp. colonizing Neem (Azadirachta indica) tree bark. GLA isolated from the test cyanobacterium was active against Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25992, Salmonella typhi (local strain), Pseudomonas aeruginosa ATCC 27853 and Enterobacter aerogenes MTCC 2822. The overproduction of GLA was also monitored by altering phosphate and nitrate levels in the nutrient medium. A doubling in phosphate concentration (58 μM) increased GLA level up to 12% over that of control cells while half of this phosphate level reduced GLA synthesis by 8%. In contrast, elevated nitrate concentrations (5 and 10 mM) stimulated biomass yield but not GLA, as the levels approximated to the nitrate-lacking control. The antibacterial potential of GLA from Fischerella sp. grown at varying P or N levels was at variance as evidenced by the diameter of inhibition zones against S. aureus. This variation in inhibition zones reflected differing levels of GLA as ascertained quantitatively by HPLC. © Springer 2005.
Identification of an antimicrobial entity from the cyanobacterium Fischerella sp. isolated from bark of Azadirachta indica (Neem) tree
(2006) Ravi K. Asthana; Arunima Srivastava; Akhilesh P. Singh; Deepali; Sureshwar P. Singh; Gopal Nath; Ranjana Srivastava; Brahm S. Srivastava
The active principle in a methanolic extract of the laboratory-grown cyanobacterium, Fischerella sp. isolated from Neem (Azadirachta indica) tree bark was active against Mycobacterium tuberculosis, Enterobacter aerogenes, Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella typhi, Escherichia coli as well as three multi-drug resistant E. coli strains in in vitro assays. Based on MS, UV, IR 1H NMR analyses the active principle is proposed to be hapalindole T having the empirical formula C21H 23N2ClSO and a molecular weight of 386 with the melting point range 179-182°C. The estimated production of Hapalindole T from the cyanobacterium is 1.25 mg g-1 lyophilized biomass. It is suggested that cyanobacteria colonizing specialized niches such as tree bark could be an antibacterial drug resource. © Springer 2006.
Isolation and identification of a new antibacterial entity from the Antarctic cyanobacterium Nostoc CCC 537
(2009) Ravi K. Asthana; Deepali; Manoj K. Tripathi; Arunima Srivastava; Akhilesh P. Singh; Sureshwar P. Singh; Gopal Nath; Ranjana Srivastava; Brahm S. Srivastava
The present study was aimed at the isolation, purification and structural elucidation of an antibacterial entity/lead molecule from the Antarctic cyanobacterium Nostoc CCC 537. A methanolic extract of the cyanobacterium was bioassayed with Enterobacter aerogenes as a target. The extract was purified by TLC, and the most active band was subjected to HPLC. The fraction (retention time 15.7 min) designated as the active principle was antibacterial towards Gram positive Mycobacterium tuberculosis H37Rv, Staphylococcus aureus ATCC 25923, Gram negative Salmonella typhi MTCC 3216, Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25992, Enterobacter aerogenes MTCC 2822 and multi-drug resistant strains of Escherichia coli GS 2003/01, 02, 03. Based on UV, IR, 1H NMR, EIMS, and ESIMS data, the structure of the active principle is proposed as 4-[(5-carboxy-2-hydroxy)-benzyl]-1,10-dihydroxy-3,4,7,11,11- pentamethyloctahydrocyclopentanaphthalene (Mr 428, Mp 243-249°C). This intracellular biomolecule is similar to anthraquinone and indane derivatives of a diterpenoid. The rate of production of the active principle currently corresponds to 1.70 mg g-1 biomass dry weight. The inherent property of Nostoc sp. to synthesise niche-specific biomolecules/lead molecules may be exploited for future drug development. © 2008 Springer Science+Business Media B.V.