POTENT BIOLOGICAL AGENT BENZIMIDAZOLE–A REVIEW

Benzimidazole nucleus is one of the most important heterocycles exhibiting remarkable pharmacological activities. Numerous method for the synthesis of benzimidazole and also their diverse reactions offer enormous scope in the field of medicinal chemistry. Various reported biological activities (analgesic, anti-inflammatory, anthelmintic, anticancer, anthelmintic, antioxidant, antitubercular, and antiviral activity) of bezimidazole are collected and summarized here. Large numbers of drugs are available to treat various diseases, but they are associated with some drawbacks like resistance, toxicities and other adverse effects. To combat with these problems there is need to discover and synthesize newer chemical entities with better efficacy and novel mechanism of action. The benzimidazole ring is an important pharmacophore in modern drug discovery. The synthesis of novel benzimidazole derivatives remains a main focus of medicinal research. There is still scope for more research work to be done in this field to find a novel agent. The versatility of new generation benzimidazole would represent a fruitful pharmacophore for further development of better medicinal agents. Therefore this substrate has a tremendous scope for the discovery of new, better, safe and more potent biological agents

Characterization of the chemical signatures of air masses observed during the PEM experiments over the western Pacific

Extensive observations of tropospheric trace species during the second NASA Global Tropospheric Experiment Western Pacific Exploratory Mission (PEM-West B) in February-March 1994 showed significant seasonal variability in comparison with the first mission (PEM-West A), conducted in September-October 1991. In this study we adopt a previously established analytical method, i.e., the ratio C2H2/CO as a measure of the relative degree of atmospheric processing, to elucidate the key similarities and variations between the two missions. In addition, the C2H2/CO ratio scheme is combined with the back-trajectory-based and the LIDAR-based air mass classification schemes, respectively, to make in-depth analysis of the seasonal variation between PEM-West A and PEM-West B (hereinafter referred to as PEM-WA and PEM-WB). A large number of compounds, including long-lived NMHCs, CH4, and CO2, are, as expected, well correlated with the ratio C2H2/CO. In comparison with PEM-WA, a significantly larger range of observed C2H2/CO values at the high end for the PEM-WB period indicates that the western Pacific was more impacted by "fresher" source emissions, i.e., faster or more efficient continental outflow. As in the case of PEM-WA, the C2H2/CO scheme complements the back-trajectory air mass classification scheme very well. By combining the two schemes, we found that the atmospheric processing in the region is dominated by atmospheric mixing for the trace species analyzed. This PEM-WB wintertime result is similar to that found in PEM-WA for the autumn. In both cases, photochemical reactions are found to play a significant role in determining the background mixing ratios of trace gases, and in this way the two processes are directly related and dependent upon each other. This analysis also indicates that many of the upper tropospheric air masses encountered over the western Pacific during PEM-WB may have had little impact from eastern Asia's continental surface sources. NOx mixing ratios were significantly enhanced during PEM-WB when compared with PEM-WA, in the upper troposphere's more atmospherically processed air masses. These high levels of NOx resulted in a substantial amount of photochemical production of O3. A lack of corresponding enhancements in surface emission tracers strongly implies that in situ atmospheric sources such as lightning are responsible for the enhanced upper tropospheric NOx. The similarity in NOx values between the northern (higher air traffic) and southern continental air masses together with the indications of a large seasonal shift suggests that aircraft emissions are not the dominant source. However, photochemical recycling cannot be ruled out as this in situ source of NOx. Copyright 1999 by the American Geophysical Union