Biomedical subjects
Publications and source records attributed to Y Venkateswarlu.
The soft coral Sinularia maxima yielded five terpenoids and one sterol, including two new furanocembranoid diterpenoids (1 and 2). The structures of these new compounds were determined by the interpretation of their spectral data.
Two new dibromotyrosine-derived metabolites (1 and 2) and the known compounds bastadin-6, bastadin-16, purealidin P, purealidin G, and aplysamine-2 and its ammonium salt have been isolated from the sponge Psammaplysilla purpurea. Compounds 1 and 2 were characterized by interpretation of their spectral data.
Three new oxygenated africanenes (1-3) have been isolated from the soft coral Sinularia dissecta and were characterized by spectral and chemical studies.
A new 1,2-dihydroisoquinoline (1) and a known isoquinolinequinone (2) have been isolated from the sponge Petrosia similis and characterized by the study of spectral data.
A new sterol, 23,24(S)-dimethylcholest-5,22-dien-3beta,7alpha-diol (1), has been isolated from the soft coral Lobophytum crassum and characterized by interpretation of spectral data.
Two new 19-oxygenated polyhydroxy steroids, 24-methylene cholest-5-en-1alpha,3beta,19-triol (1) and 24-methylene cholest-5-en-3beta,7beta,9alpha,19-tetrol (2), and three known steroids, ergost-5,24(28)-dien-3beta,19-diol (litosterol), cholest-5-en-3beta,7beta,19-triol, and ergost-5,24 (28)-dien-3beta, 7beta,19-triol, have been isolated from the soft coral Nephthea chabroli and characterized through interpretation of spectral data.
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A large number of substances of medical importance have been isolated from marine flora and fauna and their chemical structures were elucidated. Among the many compounds isolated in our laboratories only two compounds were identified as neurotoxins as they produced depolarizing effects in nerve fibers. The Xestospongin D and Araguspongin C, isolated and purified to 100% from sponge, Haliclona exigua were tested for their effects on rat brain nitric oxide synthase (NOS) activity in vitro. The results showed that NOS activity was significantly inhibited in a concentration and time dependent manner with an estimated IC50 of 31.5 and 46.5 microM for Xestospongin D and Araguspongin C, respectively, and the maximum inhibition occurred within 3 min of incubation. To explore the mechanism of action of these compounds on NOS, we have conducted kinetic studies with L-arginine, NADPH and Ca2+ in the presence of IC50 concentrations of these two compounds. The maximum velocity (Vmax) and enzyme constant (Km) were calculated using the Michaelis Menten equation. The results show that both compounds are competitive inhibitors of NOS with the substrate, L-arginine and uncompetitive with NADPH and free Ca2+. The NOS inhibition by these two compounds was similar to N omega-nitro-L-arginine methylester (L-NAME), a known inhibitor of NOS. These results suggest that the marine biomolecules Xestospongin D and Araguspongin C are in vitro modulators of neuronal NOS.
A new dibromotyrosine-derived metabolite (1a) and the known compounds aerothionin, moloka'iamine diacetate (2a), and 2,6-dibromo 4-hydroxy-4-acetamido-1,1-dimethoxy-2,5-cyclohexadiene have been isolated from the sponge Psammaplysilla purpurea and characterized by spectral studies.
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Scorpion (Buthus tamulus) venom was subjected to neutralization by treating the venom with various chemicals such as hydrochloric acid, sodium hydroxide, thiourea, formaldehyde, zinc sulphate, acetic acid and trichloroacetic acid. The venom was also subjected to heat treatment. The levels of total protein, free amino acids and protease activity in neutralized venom decreased significantly. The decrease in venom protein and free amino acids was in proportion to the duration of the heat treatment and the concentration of chemicals used except zinc sulphate, sodium hydroxide and thiourea. Protease activity of neutralized venom samples also showed a decrease except with zinc sulphate which enhanced the enzyme activity. Intramuscular injection of formaldehyde, trichlcroacetic acid and heat treated venoms into albino rats produced low mortality while thiourea and zinc sulphate were not effective in reducing the mortality. Hydrochloric acid and acetic acid treated venoms reduced the mortality by 50% with a decrease in the symptoms of envenomation. The changes were attributed to the denaturing of venom protein by chemical and heat treatments.
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