Harekrishna Jana

Synthesis, in vitro evaluation of antibacterial, antifungal and larvicidal activities of pyrazole/pyridine based compounds and their nanocrystalline MS (M = Cu and Cd) derivatives

Methyl 3,5-dimethyl pyrazole-1-dithioate (mdpa) (1), benzyl 3,5-dimethyl pyrazole-1-dithioate (bdpa) (2), 3,5-dimethylpyrazole-1-(5methyl-1H-pyrazol-3-ylmethyl)-1H-pyrazole (3), copper(II)-mdpa (4), copper(II)-bdpa (5), cadmium(II)-mdpa (6), cadmium(II)-bdpa (7), Cu2S nanoparticles (8 and 9) derived from 4 and 5, respectively, CdS nanoparticles (10 and 11) derived from 6 and 7, respectively, were synthesized to screen their antimicrobial activities. Prolonged reaction with CuCl2.2H2O and 3 followed by addition of trace amount of pyridine furnished a crystalline chloro bridged complex [Cu(μ-Cl)2(pyridine)2]n and its structure was solved by single X-ray crystallography. Antibacterial activities of all of the synthesized materials (1–12) were evaluated against Gram positive bacteria including Staphylococcus aureus and Bacillus subtilis and Gram negative bacteria including Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae and Proteus vulgaris. Fungi (Candida albicans, Aspergillus flavus) were also used to test antifungal activities with the compounds. Present study revealed that 8 shows best antibacterial activity among the present reported compounds. An excellent antifugal activity is shown by 12 emerging to be a better antibiotic than standard fluconazole. Besides fungicidal effect, 12 has promising larvicidal effect. The structure and activity relationship has been discussed.

Signal of Climate Change through Decadal Variation of Aquatic pH in Indian Sundarbans

Repeat hydrographic and time series data for 30 years in the western Indian Sundarbans exhibit direct evidence for acidification of estuarine water. The long-term trend in surface water pH is interpreted as signal of climate change and its possible causes are briefly outlined in this first-order analysis. The significant spatio-temporal variation of surface water pH can be attributed to factors like seawater intrusion into the estuary from Bay of Bengal, sewage discharge (from point and nonpoint sources) and photosynthetic activity by the mangrove vegetation that exhibit variable biomass and area around the selected stations. The sudden rise of surface water pH during 2009 in all the stations is a direct consequence of sea water intrusion during AILA, a super cyclone that hit Sundarbans on 25th May, 2009. The significant negative correlation of mangrove vegetation pool (assessed from AwiFS data for June 2010) with percentage of pH fall (r = - 0.6978; p <0.01) strongly supports the positive influence of mangrove photosynthetic activity in shifting the equilibrium towards alkalinity.

Investigating the effect of storage temperature and hot-water treatment on the microbial dynamics in edible oyster (Saccostrea cucullata)

Oysters are an important sea food all over the world apart from shrimp and crabs. They are usually sold as a live product and can be stored for several weeks before consumption. Temperature abuse during oyster post-harvest handling may allow multiplication of natural spoilage microflora as well as pathogens, which is a potential threat to consumers and/or compromising product quality. In this study, the effect of storage temperatures (25°C, 4°C, 0°C and –10°C) and boiling on the microbial quality of shell stock and shucked meats of oysters (Saccostrea cucullata) were examined. The load of total bacteria, fungi, coliform, fecal coliform, Salmonella sp. and Streptococcus sp. were comparatively higher in shucked meat than in the shell-stock at all the storage temperatures (except Vibrio sp.) and the number of the spoilage bacteria is directly proportional to the storage time but decreased with lowering of the temperature. Microbial count also observed at various interval of treatment with boiling water (100°C). During boiling water treatment of the shell-stock and shucked meats, the decimal reduction time, D-value (D100°C) for total microbes was found to be 2.7 min and 2.4 min respectively. The results indicated that oysters must be stored for a limited time as shell-stock and during cooking it should be prepared as shucked meats, and washing with boiled water is a simple method for making it microbes free.

Variation of antioxidant biomarkers in the edible oyster Saccostrea cucullata collected from three different water bodies of Sundarbans

Variations of antioxidant biomarkers such as catalase (CAT), superoxide dismutase (SOD) activities and lipid peroxidation (LPO) were studied in edible part of mangrove oyster Saccostrea cucullata, collected from three different water bodies, such as Namkhana (S-I), Frazergaunge (S-II) and Sajnekhali (S-III) of Indian Sundarbans which are exposed to different degrees of anthropogenic activity. The study was conducted for consecutive two years (2010 and 2011) in the respective water bodies. Characteristics of biomarkers in oyster from the two polluted water bodies, i.e. S-I and S-II, are similar in nature in comparison to less polluted site (S-III). The catalase, superoxide dismutase activity and lipid peroxidation in oyster flesh exhibit significant (p<0.01) spatial and temporal variation among the three stations. Oysters from S-I were significantly higher (p<0.05) in antioxidant enzyme activities than oysters from S-III, which differ in their amount of pollution sources. Maximum antioxidant enzymes activity of all collected samples were recorded in pre-monsoon time and decreased in monsoon season. But maximum lipid peroxidation was noted during monsoon followed by post-monsoon and pre-monsoon.

Status of Heavy Metal in the Lower Gangetic Delta: Implication of Acidification on Compartmentation

Increased atmospheric carbon dioxide concentrations are causing greater dissolution of carbon dioxide into the estuarine water, which is the key factor behind today’s ongoing ocean acidification and subsequent compartmentation of heavy metals in the system. We conducted a long term survey on temporal variation of pH and its impact on heavy metals in the Matla estuary, situated in the central part of Indian Sundarbans. The present study indicates the key role of acidification (major driver) in the exchange of heavy metals from sediment compartment to the overlying aquatic phase. The lowering of pH favours the process of dissolution of selected heavy metals (Zn, Cu and Pb) and promotes the transference of metallic compounds from the sediment to the aquatic phase.

Will Avicennia Alba Thrive in Climate Change Induced Salinity Rise

The effect of salinity on chlorophyll a, chlorophyll b, total chlorophyll, carotenoid and proline content of hydroponically grown seedlings of Avicennia alba was studied to observe its tolerance to changing salinity. The selected seedlings were exposed to five different salinity levels (2, 5, 10, 15 and 20 psu) for a period of 30 days and observations were done at a regular interval of 7, 14, 21 and 30 days respectively. The concentrations of chlorophyll exhibited significant positive correlations with salinity (p < 0.01). The chlorophyll a:b ratio in the plant varied between 3.04 to 3.56 through out the period of inves- tigation. The salinity fluctuation did not affect the carotenoid level and proline content in the leaves of the species as evidenced from the insignificant r values. The results show that Avicennia alba of Indian Sundarbans region can tolerate and adapt to high saline condition as witnessed in the central sector of the deltaic complex around the Matla River.