The present study evaluated phenol and m-cresol induced oxidative stress responses in the teleost fish Oreochromis mossambicus in a semi-static test system in which water was renewed every 24 h. Fishes were exposed to sublethal (1/10 of LC 50 /96 h) concentration of phenol (3.12 mg l -1 ) and m-cresol (2.2 mg l -1 ) for a period of 21 days. Significant increases in catalase (CAT) and superoxide dismutase (SOD) activities in gills, liver and kidney of treated groups represent an adaptive response to free radical toxicity. Reduction in enzyme activity shows that all reactive oxygen species (ROS) are not being quenched. Glutathione-S-transferase (GST) activity was found to be highly elevated in liver which may be due to its important role in the detoxification of xenobiotics. Total reduced glutathione glutathiore peroxidase (GSH) level was found to be highest in liver which may be an adaptive mechanism to oxidative stress. An increased hydroperoxide (HP) level was observed in liver, kidney and muscle of both the treated groups which may be attributed to the decreased glutathione peroxidase (GPx) activity observed. Increased malondialdehyde (MDA) levels in gills and liver indicates that elevated antioxidant enzyme activities were not efficient enough to prevent lipid peroxidation in these tissues. Taken as a whole, the present results seem to implicate that phenolic compounds are potent mediators of free radical generation in fish.

The green chemistry approach using plants involves phytoconstituent mediated reduction process for synthesis of nanoparticles. Biogenic Silver nanoparticles (AgNPs) were synthesized using aqueous stem extract of Ruta graveolens. The adopted biological method is compatible with green chemistry principles because the plant extract acts as a dual functional molecule: as reductant and a stabilizing agent for the synthesis of AgNPs. The UV–visible spectra confirmed that reduction of silver ions for Ruta stem extract at 485 nm on 24-hour incubation. FT-IR spectroscopic spectrum showed the peaks at 3507, 2829, 1579, 1010, 755 which are characteristic of flavonoids and terpenoids present in the stem. The zeta potential of Ruta AgNPs was found to be -35.4 mV which indicate that the nanoparticles are quite stable due to charge accumulation on its surface. The TEM micrograph reveals that the particles were of spherical shape & monodispersed, the average size of the particles is around 15 nm. Ruta AgNPs showed cytotoxicity against cancer cells and the results indicated that with the increase in Ruta AgNPs concentration there was a significant (p < 0.05) decrease in cell viability of HepG2 as compared to control. The antioxidant activity of Ruta AgNP was confirmed by ABTS radical scavenging activity. Ruta AgNPs may provide novel resources for the evaluation and development of newer, safer, and effective antimicrobial and antiproliferative drug formulations.