Phytochemical and antioxidant studies of Laurera benguelensis growing in Thailand.
The aim of this study was to investigate metabolites of the lichen Laurera benguelensis. A high-performance liquid chromatographic (HPLC) method has been developed for the characterization of xanthones and anthraquinones in extracts of this lichen. Lichexanthone, secalonic acid D, norlichexanthon, parietin, emodin, teloschistin and citreorosein were detected in the lichen samples, which were collected from two places in Thailand. Components of the lichen were identified by relative retention time and spectral data. This is the first time that a detailed phytochemical analysis of the lichen L. benguelensis was reported and this paper has chemotaxonomic significance because very little has been published on the secondary metabolites present in Laurera species. Some of the metabolites were detected for the first time in the family Trypetheliaceae. The results of preliminary testing of benzene extract and its chloroform and methanol fractions showed that all samples showed a weak radical scavenging activity. The chloroform extract showed the highest antioxidant activity.
Antioxidant xanthones from Garcinia subelliptica
Abstract From the woods of Garcinia subelliptica four new xanthones, garciniaxanthone C, 1,2,5-trihydroxyxanthone, 2,6-dihydroxy-1,5-dimethoxyxanthone and 1,2-dihydroxy-5,6-dimethoxyxanthone have been isolated along with a new benzophenone derivative, 4′,6-dihydroxy-2,3′4-trimethoxybenzophenone. Their structures have been determined on the basis of mainly spectroscopic data and some chemical reactions. Antioxidative properties of all the isolated xanthones have been evaluated in vitro using three assay systems to measure antilipidperoxidation, free radical and superoxide anion scavenging activity.
Effects of dimethyl sulfoxide and other dipolar aprotic solvents on rat hepatic adenylate cyclase. Potentiating effects on glucagon and guanylylimidodiphosphate stimulation
SummaryThe actions of dimethyl sulfoxide (DMSO), acetone and two other aprotic solvents on the activity of rat hepatic adenylate cyclase were studied in order to detect their possible effects on both hormonal and nonhormonal enzyme stimulation. The glucagonor guanylylimidodiphosphate [Gpp(NH)p]-stimulated activity was significantly increased by all DMSO concentrations (0.08–2.57 M) while the highest concentrations of this solvent decreased the enzyme activity stimulated by sodium fluoride. The effect of DMSO on adneylate cyclase activity is reversible and the stimulatory effect of this drug can be seen even on adenylate cyclase activity in the persistent active state induced by preincubation of the enzyme with Gpp(NH)p. An increase in adenylate cyclase activity stimulated by glucagon or Gpp(NH)p was also seen after the addition of other aprotic solvents (acetone, acetonitrile and dimethylformamide) to the assay system. These effects of aprotic solvents on the rat hepatic adenylate cyclase activity may be caused by an increase of membrane fluidity and facilitated movement of the adenylate cyclase subunits in the plane of the cell membrane.