In vitro antioxidant and in vivo prophylactic effects of two gamma-lactones isolated from Grewia tiliaefolia against hepatotoxicity in carbon tetrachloride intoxicated rats

Grewia tiliaefolia is widely used in traditional Indian medicines to cure jaundice, biliousness, dysentery and the diseases of blood. Bioassay-guided fractionation of methanolic extract of the G. tiliaefolia bark has resulted in the isolation of D-erythro-2-hexenoic acid gamma-lactone (EHGL) and gulonic acid gamma-lactone (GAGL). Hepatoprotective activity of the methanolic extract and the isolated constituents were evaluated against CCl4-induced hepatotoxicity in rats. The treatment with methanolic extract, EHGL and GAGL at oral doses of 100, 150 and 60 mg/kg respectively with concomitant CCl4 intraperitoneal injection (I ml/kg) significantly reduced the elevated plasma levels of aminotransferases, alkaline phosphatase and the incidence of liver necrosis compared with the CCl4-injected group without affecting the concentrations of serum bilirubin and hepatic markers. EHGL and GAGL significantly inhibited the elevated levels of thiobarbituric acid reactive substances and glutathione in liver homogenates. Histology of the liver tissues of the extract and isolated constituents treated groups showed the presence of normal hepatic cords, absence of necrosis and fatty infiltration as similar to the normal control. The results revealed that the hepatoprotective activity of EHGL is significant as similar to the standard drug silymarin. To clarify the influence of the extract and isolated constituents on the protection of oxidative-hepatic damage, we examined in vitro antioxidant properties of the test compounds. The extract and the constituents showed significant free radical scavenging activity. These results suggest that the extract as well as the constituents could protect the hepatocytes from CCl4-induced liver damage perhaps, by their anti-oxidative effect on hepatocytes, hence eliminating the deleterious effects of toxic metabolites from CCl4, (C) 2009 Elsevier B.V. All rights reserved.

Heterogeneous permanganate oxidations: Synthesis of medium ring keto-lactones via substituent directed oxidative cyclisation

Homoallyl alcohols 4a-b and 5a-b undergo smooth oxidative cyclisation to give the corresponding ring enlarged keto-lactones under heterogeneous permanganate oxidation conditions.

1,3-Dipolar cycloaddition reaction of ?,?-unsaturated esters and lactones with diazomethane

1,3-Dipolar cycloaddition of diazomethane to the alpha,beta-unsaturated esters and lactones such as 2-4, 6-8, 10 and 13 occurs in a stereoselective manner affording conjugated Delta(2)-pyrazolines. E and Z isomers of D-mannitol lead to identical product which was cyclised to investigate the absolute stereochemistry of the product. The regiospecificities of all the reactions are consistent with FMO coefficients obtained through AM1 calculations.

Catalytic Enantioselective Halocyclizations beyond Lactones: Emerging Routes to Enantioenriched Nitrogenous Heterocycles

Electrophilic halogen-induced reactions of unactivated olefins are an important class of transformations, whose catalytic enantioselective variants have surfaced during the past few years as effective means of olefin heterodifunctionalization. This article covers important developments in the area of enantioselective halocyclizations, specifically in the context of the synthesis of nitrogenous heterocycles.

Solution structural features of N-acyl homoserine lactones

Here we demonstrate that in interbacterial quorum signal moderators, N-acylhomoserine lactones (AHLs), the stabilization of bioactive pharmacophore lactone against lysis is through the e(-) withdrawing N-acyl motif which reduces lactone carbonyl polarization. This lysis is assisted by weak (<0.05 kcal mol(-1)) contacts between N-acyl O and lactone C'. The interactions that preclude this weak contact, in the free and receptor-bound AHLs, improve lactone halflife and hence are key to the design of the antibacterial AHL analogues. (C) 2015 Elsevier Ltd. All rights reserved.

Synthesis and characterization of (C5H9C9H6)(2)Yb(THF)(2)(II) (1) and [(C5H9C5H4)(2)Yb(THF)](2)O-2 (2), and ring-opening polymerization of lactones with 1

Reaction of YbI2 with two equivalents of cyclopentylindenyl lithium (C5H9C9H6Li) affords ytterbium(II) substituted indenyl complex (C5H9C9H6)(2)Yb(THF)(2) (1) which shows high activity to ring-opening polymerization (ROP) of lactones. The reaction between YbI2 and cyclopentylcyclopentadienyl sodium (C5H9C5H4Na) gives complex [(C5H9C5H4)(2)Yb(THF)](2)O-2 (2) in the presence of a trace amount of O-2, the molecular structure of which comprises two (C5H9C5H4)(2)Yb(THF) bridged by an asymmetric O-2 unit. The O-2 unit and ytterbium atoms define a plane that contains a C-i symmetry center.