EVALUATION OF IN VITRO FREE RADICAL SCAVENGING ACTIVITY OF LEAF EXTRACT FRACTIONS OF MANILKARA HEXANDRA (ROXB) DUBARD IN RELATION TO TOTAL PHENOLIC CONTENTS

Objective: To evaluate in vitro free radical scavenging, reducing power and total antioxidant activity of leaf extract fractions of Manilkara hexandra (Roxb.) Dubard in relation to their total phenolic contents. Methods: 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging, Fe3+reducing power and the total antioxidant activities of the five extract fractions (petroleum ether extract fraction, PEF; chloroform extract fraction, CHF; ethyl acetate extract fraction, EAF; methanolic extract fraction, MEF; aqueous extract fraction, AQF) were performed and the results were expressed as ascorbic acid equivalent and the total phenolic content was also measured and the data expressed as tannic acid equivalent. Results: Different extract fractions show the varied degree of free radical scavenging and reducing potentials and the order determined as MEF>AQF>EAF>CHF>PEF. The highest total antioxidant activity, 60.37±6.24 mg of ascorbic acid equivalent, and also the highest total phenolic content, 89.91±8.72 mg of tannic acid equivalent, were estimated in per gram of the leaf MEF. The MEF showed the maximum DPPH free radical scavenging activity, Fe3+reducing power and the total antioxidant activities than all the other extract fractions tested. Conclusion: In vitro free radical scavenging and reducing potentials of the leaf extract fractions of M. hexandra were explored here and the leaf MEF identified as the most potential extract fraction contained the highest quantities of antioxidants and that positively correlate with the presence of relatively higher quantities of total phenolic contents.Â

Integrated graphene quantum dot decorated functionalized nanosheet biosensor for mycotoxin detection

Decoration of graphene quantum dots (GQDs) on molybdenum disulfide (MoS2) nanosheets serves as an active electrode material which enhances the electrochemical performance of the analyte detection system. Herein, ionic surfactant cetyltrimethylammonium bromide (CTAB)-exfoliated MoS2 nanosheets decorated with GQD material are used to construct an electrochemical biosensor for aflatoxin B1 (AFB1) detection. An antibody of AFB1 (aAFB1) was immobilized on the electrophoretically deposited MoS2@GQDs film on the indium tin oxide (ITO)-coated glass surface using a crosslinker for the fabrication of the biosensor. The immunosensing study investigated by the electrochemical method revealed a signal response in the range of 0.1 to 3.0 ng/mL AFB1 concentration with a detection limit of 0.09 ng/mL. Also, electrochemical parameters such as diffusion coefficient and heterogeneous electron transfer (HET) were calculated and found to be 1.67 x 10(-5) cm(2)/s and 2 x 10(-5)cm/s, respectively. The effective conjugation of MoS2@GQDs that provides abundant exposed edge sites, large surface area, improved electrical conductivity, and electrocatalytic activity has led to an excellent biosensing performance with enhanced electrochemical parameters. Validation of the fabricated immunosensor was performed in a spiked maize sample, and a good percentage of recoveries within an acceptable range were obtained (80.2 to 98.3%)

Potential use of sugar binding proteins in reactors for regeneration of CO(2 )fixation acceptor D-Ribulose-1,5-bisphosphate

Sugar binding proteins and binders of intermediate sugar metabolites derived from microbes are increasingly being used as reagents in new and expanding areas of biotechnology. The fixation of carbon dioxide at emission source has recently emerged as a technology with potentially significant implications for environmental biotechnology. Carbon dioxide is fixed onto a five carbon sugar D-ribulose-1,5-bisphosphate. We present a review of enzymatic and non-enzymatic binding proteins, for 3-phosphoglycerate (3PGA), 3-phosphoglyceraldehyde (3PGAL), dihydroxyacetone phosphate (DHAP), xylulose-5-phosphate (X5P) and ribulose-1,5-bisphosphate (RuBP) which could be potentially used in reactors regenerating RuBP from 3PGA. A series of reactors combined in a linear fashion has been previously shown to convert 3-PGA, (the product of fixed CO(2 )on RuBP as starting material) into RuBP (Bhattacharya et al., 2004; Bhattacharya, 2001). This was the basis for designing reactors harboring enzyme complexes/mixtures instead of linear combination of single-enzyme reactors for conversion of 3PGA into RuBP. Specific sugars in such enzyme-complex harboring reactors requires removal at key steps and fed to different reactors necessitating reversible sugar binders. In this review we present an account of existing microbial sugar binding proteins and their potential utility in these operations

Electric field induced instabilities: waves and stationary patterns

We examine a prototypical ionic reaction-diffusion system involving the well-known iodate-arsenous acid reaction in an electric field at a constant current density. By taking into consideration of the spatial inhomogeneities in electric field intensity and charge density due to ionic migration and diffusion using charge balance condition, we look for the different instability regions in the appropriate parameter space. We show that the model admits of both absolute and convective instability resulting in the development of propagating waves and also stationary spatial patterns at times

Thermodiffusion-induced instabilities in reactive systems

We examine the influence of a thermal gradient on a classical reaction-diffusion system. The different instability regions in the appropriate parameter space are examined. We show how the imposed temperature gradient destabilizes a chemical front via the Soret effect, giving rise to both absolute and convective instability

Kinetics of oxidation of iodide ion by <i>trans-</i>(cyclohexane-l ,2-diamine N,N,N',N' tetraacetato)manganate(III) weakly acidic solution

531-533Kinetics of redox reaction between Iˉ and [MnIII(cdta)]ˉ has been investigated in aqueous solution by a stopped-flow technique at pH 3.26 (acetate buffer) and at 30, 35 40 and 45°C. The overall reaction is third order-first order in [MnIII(cdta)ˉ] and second order in [Iˉ]. Though no direct evidence has been obtained, an inner-sphere mechanism has been proposed based on the lability of the complex and is supported by the large negative value of ΔS# (-168 ± 6) JK-1 mol-1

Effects of delay in a reaction-diffusion system under the influence of an electric field

We investigate the consequences of delay in the iodate–arsenous acid reaction under the influence of an electric field at a constant current density. Using the charge balance condition, we show how the electric field may induce an intrinsic delay in the system, which gives rise to instability. The different instability regions in the appropriate parameter space are examined. We show how the delay incites an absolute instability in a system otherwise displaying varied wave-front characteristics, viz., convective and absolute instabilities and also stationary patterns

Magnetic field induced pattern formation in reactive membranes

The effect of magnetic field on lipid bilayers has been a subject of interest to experimentalists in recent years. Here we examine a fluctuation model of reactive bilayer membranes, taking into view the composition-curvature correlation in the presence of a homogeneous magnetic field. We show how the strength of the magnetic field in combination with the intensity of reaction induces instability into the system, at times leading to stationary pattern formation

Kinetics of electron transfer between bis( 2,2' -bipyridine )manganese(III) complex and thioureas in aqueous perchlorate media

43-46Kinetics of the redox interactions of thiourea and its N-substituted derivatives with manganese(III) complex of 2,2'-bipyridine has been investigated in aqueous solution by a stopped-flow technique in the acid range [H+], 0.10-0.50 mol dm-3 at l= 1.0 mol dm -3 (NaClO4) and at 30°C. A rapid initial increase in absorbance is followed by a slower decay of the formed species for all the four thioureas. Both the reaction steps are analysed and an inner sphere mechanism has been proposed for these reactions. The reactivity order for these thiourea derivatives is: ptu >tu >mtu >atu, and this bears a consequence to their substituent effects

Noise-induced instability: an approach based on higher-order moments

Noise-induced transitions in the organization of systems far from equilibrium have been of vital interest. Although the effects of additive and multiplicative noise have been widely studied, it is only the multiplicative noise that can be dealt with within the scope of a linear analysis of first moments of the spatiotemporal perturbations, by the application of Novikov's theorem. For the case of additive noise, the corresponding straightforward linear analysis of the first moment throws no light on the effect of the noise on stability conditions. We propose here a simple approach based on higher-order moments to show how additive noise can give rise to noise-induced instability in spatially extended systems, at times leading to pattern formation. Our theoretical analysis is corroborated by numerical simulations on two simple one-component reaction-diffusion systems in two dimensions