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 identifed by relative retention time and spectral data. This is the frst time that a detailed phytochemical analysis of the lichen L. benguelensis was reported and this paper has chemotaxonomic signifcance because very little has been published on the secondary metabolites present in Laurera species. Some of the metabolites were detected for the frst 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.

Anti-head lice effect of Annona squamosa seeds.

The present study focused on the separation and identification of the active compounds against head lice from the hexane extract of Annona squamosa L seed. Chromatographic and spectroscopic techniques revealed that two major compounds of the hexane seed extract were oleic acid and triglyceride with one oleate ester. The yields of these compounds were 13.25% and 7.74% dry weight, respectively. The compounds were tested in vitro against head lice, comparing to the crude hexane extract of the seed. The triglyceride with one oleate ester and the crude hexane extract diluted with coconut oil 1:1. These compounds were found to kill all tested head lice in 49, 11 and 30 minutes, respectively. The triglyceride ester can be used as a marker for quantitative analysis of the active compound for quality control of the raw material A. squamosa seed and its extract. This first finding will be useful for quality assessment and the chemical stability of the antihead lice preparation from this plant.

Barakol contents in fresh and cooked Senna siamea leaves.

Senna siamea (Lam.) Irwin and Barneby is a medicinal plant popularly used in Thailand. Young leaves and/or young flowers of this plant have been consumed by Thai people as a Khi Lek curry for a long time. The fresh young leaves and flowers are boiled with water 2-3 times to get rid of the bitterness and the boiled mush is used for curry cooking. Barakol, a major constituent of Senna siamea leaves was analyzed for its content in the fresh young leaves, the boiled leaves and the boiled filtrates by a high-performance thin-layer chromatographic method. Fresh young leaves of S. siamea contained 0.4035% w/w barakol. The amount of barakol in the first and second boiled filtrates were 0.2052 and 0.1079% fresh weight, while the first and second boiled leaves samples were 0.1408 and 0.0414% fresh weight, respectively. The results show the process of preparation of Khi Lek curry by boiling S. siamea young leaves twice with water reduced barakol content up to 90% and the content of barakol in boiled leaves used for curry has much less tendency to cause liver toxicity. This may explain the reason why Thai Khi Lek curry has not caused hepatotoxicity, unlike S. siamea leaves consumed as a powdered capsule.

Comparison of free radical scavenging activity of siamese neem tree [azadirachta indica A. juss var. siamensis valeton] leaf extracts prepared by different methods of extraction

The aim of this study was to investigate the antioxidant activity of the aqueous extracts of leaves of Siamese neem tree [Azadirachta indica A. Juss var. siamensis Valeton] from several extracting and drying methods using 2,2-diphenyl-1-picrylhydrazyl [DPPH]-scavenging assay. The leaves of Siamese neem tree were extracted using percolation, decoction, maceration, soxhlet extraction, freeze drying or spray drying methods. The extract was tested for antioxidant activity using DPPH-scavenging assay. Thin-layer chromatography of the extract from decoction was also investigated. The freeze drying method gave the highest yield [51.50%, w/w] of crude extract, while decoction gave the most effective DPPH-scavenging activity [EC[50]: 31.4 micro g/ml]. Thin-layer chromatography analysis was used to screen the leaf extract obtained using decoction, and the chromatogram showed spots corresponding to quercetin and rutin flavonoids which exhibited antioxidant activities [EC[50]: 2.29 and 34.67 micro g/ml, respectively]. Siamese neem tree leaf extracts possessed free radical scavenging activity against the DPPH radical. The most active extract was obtained with the leaf decoction method. It showed antioxidant activity with EC[50] of 31.4 micro g/ml