Anti-inflammatory activity of piperine

Piperine (1-peperoyl piperidine) was isolated from Piper nigrum Linn for the evaluation of anti-inflammatory activity in rats. Different acute and chronic experimental models like carrageenin-induced rat paw edema, cotton pellet granuloma, and croton oil-induced granuloma pouch, were employed. Simultaneously, biochemical estimations were made to elucidate the underlying mechanism of the action. Piperine acted significantly on early acute changes in inflammatory processes and chronic granulative changes. It also acted partially through stimulation of pituitary adrenal axis. Exudative changes in both acute and chronic models, however, were insignificant.     

alpha-Santonin 1,2-reductase and its role in the formation of dihydrosantonin and lumisantonin by Pseudomonas cichorii S

1,2-Dihydrosantonin is the first stable product in the degradative pathway of alpha-santonin by Pseudomonas cichorii S. Its formation is catalyzed by an oxidoreductase, which is NADH or NADPH dependent and has an apparent Km value of 66.66 microM for santonin and 44.33 microM for NADH. The enzyme activity is stable at pH 6.0, 7.0, and 8.0, and is not affected by EDTA and divalent metal ions. It is postulated that the enzymic reduction of santonin occurs via formation of a transient zwitterionic intermediate, which undergoes nonenzymatic 1,4-sigmatropic rearrangement to yield lumisantonin during the solvent extraction process. Lumisantonin is, thus, not a true metabolic intermediate but an artifact.     

Mitochondrial Complex I Impairment and Nitrate Reductase Activity in Leaves of Nicotiana sylvestris

Loss of major mitochondrial complex I subunit Nad 7 in the leaves of CMS II mutant of Nicotiana sylvestris caused increase in both in vivo and in vitro nitrate reductase activities and the per cent activation state of NR was also higher in CMS II as against wild type. The differences suggest a possibility for export of mitochondrial NADH due to impairment of complex I, a major and high affinity sink for NADH. Loss of complex I subunit also resulted in constitutive expression of alternate oxidase (Aox) thereby providing a mechanism for continuous supply of carbon skeletons required for nitrate assimilation. The possibility of close coordination between mitochondrial redox perturbation and nitrate reduction and its further assimilation is discussed.