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.
Inhibition of Fungal Growth by Water Extracts from the Lichen Nephroma Arcticum
Abstract Water extracts from Nephroma arcticum were prepared and tested for inhibitory effects against various yeast, mould, blue-stain and rot fungi. A water extract from Peltigera aphthosa was used as a reference. Two different diffusion assays were used, wells (cupplate method) and droplets (drop-plate method). For the majority of fungi studied using the former method there were clear zones with a sharp boundary (fungicidal effect), whereas the latter method yielded more or less hazy zones with inhibition or reduction in growth (fungistatic effect). No clear or hazy zones were seen with the extract from P. aphthosa. For Candida glabrata E, Saccharomyces cerevisiae K and Hormonema dematioides S there were clear zones for both methods. The MIC (Minimum Inhibitory Concentration) values were determined in liquid medium for S. cerevisiae K and C. glabrata E and were, respectively, 1 and 10 mg ml−1 of a crude extract from N. arcticum. The MFC (Minimum Fungicidal Concentration) values were found to be identical to the MIC values.
Comparative study of the molecular species of chloropropanediol diesters and triacylglycerols in milk fat
In an effort to establish the origin of the fatty acid esters of 3-chloropropanediol, which recently have been isolated in small amounts from goat milk, we compared the molecular species composition of the chlorohydrin diesters and of goat milk triacylglycerols. The chloropropanediol diesters were found to be composed of molecular species containing C10−C18 fatty acids and corresponded closely in carbon number to those calculated for the long chain sn-1,2-diacyl-glycerol moieties of goat milk triacylglycerols. The molecular species of goat milk total triacylglycerols contained C4−C18 fatty acids. It is suggested that triacylglycerols and chloropropanediol diesters are derived from the same pool of long chain fatty acids. A molecular distillate of bovine milk fat did not contain chloropropanediol diesters, while the available samples of human milk fat were shown to contain alkyldiacylglycerols as the major components of a neutral lipid fraction corresponding in polarity to the chloropropanediol diesters.