Sun-screening bioactive compounds mycosporine-like amino acids in naturally occurring cyanobacterial biofilms: role in photoprotection.

AIMS: To investigate the occurrence of UV sunscreening biomolecules and their role in photoprotection in cyanobacterial biofilms growing in brightly lit habitats with high UV fluxes. METHODS AND RESULTS: High performance liquid chromatography with photodiode-array and mass spectrometry revealed the presence of mycosporine-like amino acids (MAAs) shinorine (λ(max) 334 nm, m/z 333), porphyra-334 (λ(max) 334 nm, m/z 347), mycosporine-glycine (λ(max) 310 nm, m/z 246) and palythinol (λ(max) 332 nm, m/z 303). Two unknown MAAs with λ(max) at 320 (m/z 289) and 329 nm (m/z 318) were also found. Biosynthesis of MAAs was found to increase with increase in exposure time under UV radiation. The MAAs from biofilms showed efficient radical scavenging activity as well as photoprotective potential on the survival of UV-treated Escherichia coli cells. CONCLUSIONS: Biosynthesis of photoprotectants is an important mechanism to prevent photodamage in Cyanobacteria. UV-induction and photoprotective function of MAAs may facilitate them to perform important ecological functions under harsh environmental conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: There are very few reports on qualitative and quantitative characterization of different MAAs in cyanobacterial biofilms. Due to strong UV absorption and photoprotective function, MAAs may be used as an active ingredient in cosmetic and other pharmaceutical industries.

Fractal growth kinetics and electric potential oscillations during electropolymerization of pyrrole.

Fractal growth, growth kinetics, and electrical conductivity of aggregates obtained during electropolymerization in the systems (A) pyrrole-4-toluene sulfonic acid silver salt (4-TSS)-acetonitrile, (B) pyrrole-4-TSS-ZnSO(4)-acetonitrile, and (C) pyrrole-4-TSS-aniline-acetonitrile were investigated. In the case of system (A), effect of [4-TSS], [pyrrole], field intensity, and solvents H(2)O and CH(3)OH on morphology, fractal character, and growth kinetics was also studied. Fractal growth data were examined in detail. During studies on system (A), electric potential oscillations were observed and subjected to detailed study. The results indicate that fractal growth pattern and electric potential oscillations are inter-related. The mechanism of development of fractal growth, dendritic structure, and electric potential oscillations is discussed in terms of diffusion-limited aggregation and modified Diaz's mechanism, which explains the random movement of radical cations.

Dynamic instability at liquid/vapor interface far from equilibrium.

Attempt has been made to elucidate the mechanism of electric potential oscillations at oil-aqueous solution interface involving adsorption at oil-vapor interface on a semi-theoretical basis. The mechanism stipulates adsorption of ammonia, amines and pheromones at the liquid-vapor interface followed by transfer of ions through membrane-aqueous solution interface and subsequent interaction of ammonium (amine) ions and carbocations from pheromones with diffusing halide ions from the bulk. Relationship of the above mechanism with sensing mechanism of smell by olfactory nerves has also been pointed out.

Oscillatory phenomena at liquid-liquid interfaces.

The mechanism of (i) Yoshikawa and Matsubara liquid-liquid interface oscillators and (ii) density/salt-water oscillators has been investigated. A modified simple mathematical formalism of both has been presented. Qualitative support for the model is provided by the available experimental results.

Dual control mechanism in a Belousov-Zhabotinskii (B-Z) oscillator with glucose and oxalic acid as a double substrate.

Oscillations in a Belousov-Zhabotinskii (B-Z) system having oxalic acid (OA) and glucose (G) as a mixed organic substrate, neither of which acts as a bromine scavenger, have been investigated. Studies have been performed for (i) varying the concentration of G while keeping the OA concentration fixed and (ii) varying OA but keeping G fixed in a batch reactor. In both cases upper and lower critical limits occur, between which oscillations are observed. Both single and double frequency oscillations have been observed in a wide range of concentrations of G as well as of OA. The induction period in most of the cases was <1 min. When G is fixed and OA is varied, the time pause between the sequential oscillations increases with an increase in OA. On the other hand when OA is fixed and G is varied, the time-pause decreases with an increase in G. The first type of oscillation is Br(-)-controlled, whereas the second is non-Br(-)-controlled. The order of addition of G and OA in the last has no influence on the induction period. It influences, however, the oscillatory characteristics. Br(2) evolution in the G + OA + Ce(4+) + BrO(3)(-) + H(2)SO(4) reaction system has been investigated spectrophotometrically. ESR and polymerization studies indicate the important role of free radicals in influencing the reaction mechanism. A tentative dual control mechanism has been suggested involving autocatalysis of HBrO(2) and BrO2*.

Membrane oscillations involving electrokinetic phenomena.

Semi theoretical models have been proposed to account for the mechanism of membrane oscillations involving, electrokinetic phenomena in systems where (i) concentration difference deltaC is finite and deltaP is varying but the current is fixed, and (ii) deltaC=0, pressure difference deltaP is fixed across the membrane and imposed current is fixed. The formalism leads to the van der Pol equation in both cases. Computer simulation has also been attempted, which indicates oscillations in the former case.

Interface-mediated oscillatory phenomena.

Oscillatory transport processes which occur in the far from equilibrium region have assumed great significance from the viewpoint of science of complexity. Oscillatory phenomena in the chemical reaction systems have been subjected to intense investigations both from theoretical and experimental angles. In the present review an effort has been made to bring transport processes other than conventional chemical reactions into focus: transport processes mediated by solid-liquid and liquid-liquid interfaces have been discussed. Transport through membranes including liquid membranes, liquid-liquid interfaces and the recently reported hydrodynamic oscillator have been covered. Applications of these systems in areas such as fabrication of sensors, phase transfer catalysis and, of course, the obvious biological action, e.g. excitation of biomembranes and tissues, have been reviewed. Theoretical frameworks proposed to rationalize the phenomena have also been critically reviewed.

Triterpenoid Saponins from Caltha palustris.

Three triterpenoid saponins, hederagenin-3- O-alpha- L-arabinopyranoside, oleanolic acid-3- O-alpha- L-rhamnopyranosyl-(1-->2)-alpha- L-arabinopyranoside and hederagenin-3- O-alpha- L-rhamnopyranosyl-(1-->2)-alpha- L-arabinopyranoside, have been isolated from CALTHA PALUSTRIS (Ranunculaceae). The structures were determined by spectroscopic analysis of the acetates.

Dihydroflavanonols from Cedrus deodara, A (13)C NMR study.

High resolution (13)C NMR study of taxifolin, cedeodarin, cedrin and their methyl ethers allowed unambiguous placement of the Me in 5,7-dihydroxyflavanonol nucleus, besides providing other valuable information on the substitution pattern in the molecule.

Antileukemic and other constituents of Tithonia tagitiflora Desf.

Phytochemical investigation of Tithonia tagitiflora has led to isolation of six new germacranolides, tagitinins A, B, C, D, E, AND F, beta-sitosterol, and its beta-D-glucoside. Among these, tagitinin F possesses antileukemic activity.

Spasmolytic constituents of Cedrus deodara (Roxb.) Loud: pharmacological evaluation of himachalol.

Himachalol has been identified as the major antispasmodic constituent in the wood of Cedrus deodara. The pharmacological studies of himachalol on various isolated smooth muscles (guinea pig ileum, rabbit jejunum, rat uterus, and guinea pig seminal vesicle) and against different agonists (acetylcholine, histamine, serotonin, nicotine, and barium chloride) indicated spasmolytic activity similar to that of papaverine. It was a more potent antagonist of barium chloride-induced spasm of guinea pig ileum than papaverine but less effective in reverting a similar spasm of rabbit jejunum and had no relaxing effect alone. In the conscious immobilized cat, intragastric administration of himachalol or papaverine (100 mg/kg) produced equal inhibition of carbachol-induced spasm of the intestine, lasting about 2 hr, but himachalol had a faster onset of action. Himachalol was devoid of spasmolytic effect on the bronchial musculature of guinea pig but was 3.3 times more potent than papaverine in antagonizing epinephrine-induced contraction of the guinea pig seminal vesicle. Intravenous injection of himachalol (3-10 mg/kg) in the cat produced a dose-dependent fall in blood pressure and an increased femoral blood flow.