A. K. Ghosh

Vanillin as an antioxidant in rat liver mitochondria: inhibition of protein oxidation and lipid peroxidation induced by photosensitization.

Using rat liver mitochondria, as model systems, we have examined the ability of the natural compound and the food-flavoring agent, vanillin to protect membranes against oxidative damage induced by photosensitization at concentrations normally used in food preparations. Vanillin, at a concentration of 2.5 mmol/L, has afforded significant protection against protein oxidation and lipid peroxidation in hepatic mitochondria induced by photosensitization with methylene blue plus light. The effect observed was both time- and concentration-dependent. The inhibitory effect is similar to ascorbic acid and the singlet oxygen quencher, diazabicyclo[2.2.2]octane (DABCO) but less effective than sodium azide and glutathione. Examination of possible mechanisms responsible for the observed protection, showed that vanillin has a significant ability to quench singlet oxygen (1O2), a reactive species responsible for damage induced during photosensitization by Type II mechanism. Hence, this flavoring compound, due to its antioxidant ability, may have potential to prevent oxidative damage to membranes in mammalian tissues and thereby the ensuing diseased states.

Effect of vanillin on methylene blue plus light-induced single-strand breaks in plasmid pBR322 DNA.

The ability of vanillin (4-hydroxy-3-methoxybenzaldehyde), a naturally occurring food flavouring agent, in inhibiting photosensitization-induced single-strand breaks (ssbs) in plasmid pBR322 DNA has been examined in an in vitro system, independent of DNA repair/replication processes. Photosensitization of DNA with methylene blue, visible light and oxygen, induced ssbs resulting in the production of open circular form (OC form) in a concentration-dependent manner. The yield of OC form induced by photosensitization was increased several-fold by deuteration of the buffer and was found to be inhibited by sodium azide, a scavenger of singlet oxygen (1O(2)). Vanillin, per se, did not induce but inhibited photosensitization-induced ssbs in plasmid DNA, at millimolar concentrations. The inhibitory effect of vanillin was both concentration- and time-dependent. On a molar basis, vanillin was, however, less effective than trolox, a water-soluble analogue of alpha-tocopherol. Photosensitization by methylene blue system generates singlet oxygen, as one of the major components of ROS. Therefore, interaction of singlet oxygen with vanillin was investigated. The rate constant of vanillin with 1O(2) was estimated to be 5.93x10(7)M(-1)s(-1) and that of sodium azide as 2. 7x10(8)M(-1)s(-1). The present investigations show that vanillin can protect against photosensitization-induced ssbs in the plasmid pBR322 DNA, and this effect may partly be due to its ability to scavenge 1O(2).

Antidiabetic Efficacy of Enicostemma littorale Methanol Extract in Alloxan-Induced Diabetic Rats

The glucose lowering and antioxidant effect of a methanol extract of Enicostemma littorale Blume was evaluated in alloxan-induced diabetic rats. Administration of methanol extract (2.5 g/kg body weight/day) to diabetic rats for 20 days reduced blood glucose levels from 466.50 ± 37.07 to 237.20 ± 28.22 (P < 0.01). E. littorale also increased the serum insulin levels of diabetic rats and improved the antioxidant status of diabetic rats. Extract treatment to the diabetic rats significantly increased reduced glutathione levels and decreased erythrocyte catalase activity and lipid peroxidation. These results support the use of E. littorale as an antidiabetic agent by traditional healers in rural pockets of Gujarat.

A STRONG MOTION MODEL OF THE 2004 GREAT SUMATRA EARTHQUAKE: SIMULATION USING A MODIFIED SEMI EMPIRICAL METHOD

This paper presents a simplified technique to simulate strong ground motion from a finite source of an earthquake. The simplified technique is based on modifications made in the semi empirical technique given by Midorikawa [1993] and later modified by Joshi and Midorikawa [2004]. Modifications in this technique have been made to consider the effect of radiation pattern and seismic moment of the target earthquake. The coastal region of Sumatra Island was struck by a great earthquake of magnitude 9.0 (Mw) on 26th December, 2004. This earthquake is known for its release of high amount of energy and the devastating Tsunami. This earthquake was recorded at several broadband stations including a nearest broadband station located in Indonesia. The source of this earthquake is modeled by a finite rectangular rupture plane. Various locations of nucleation point and different values of rupture velocity have been tested before finalizing the rupture responsible for this earthquake. Iterative modeling and comparison of simulated and observed record due to final model suggests that the rupture initiated at the western end of the rupture plane at a depth of 38 km and started propagating in all direction with a rupture velocity of 3.0 km/s. The final model has been used to simulate record at MDRS and VISK stations located at the coastal region of India and simulated records are compared with observed records at these stations. The comparisons confirm the suitability of final model for predicting strong ground motion and the efficacy of the approach in modeling great earthquake. Strong ground motion has been simulated for the Sumatra earthquake of 26th December, 2004 at various hypothetical stations surrounding the final model of rupture plane. The distribution of peak ground acceleration in the near source region has been computed from simulated record at these stations. The isoacceleration contours shows that high peak acceleration zones of the order of > 2 g are observed in the source zone of this earthquake which gradually decreases with distance. Using the parameters of final model of the Sumatra earthquake a great hypothetical earthquake at northern segment of Andaman ridge has been modeled and records have been simulated at Port Blair (POR) station located in the Andaman Island, India. The simulated records shows that peak ground acceleration of the order of 1.4 g can be observed at POR station due to a hypothetical earthquake in the Andaman Island suggesting high seismic hazard in this region.