Biosynthesis of a syringyl 8-O-4′ neolignan in Eucommia ulmoides: formation of syringylglycerol-8-O-4′-(sinapyl alcohol) ether from sinapyl alcohol

To investigate the biosynthesis and stereochemistry of syringylglycerol-8-O-4′-(sinapyl alcohol) ether (SGSE), a syringyl 8-O-4′ neolignan, feeding experiments and enzyme assays using Eucommia ulmoides were carried out. Diastereoselective formation of erythro-SGSE was found. When [8-¹⁴C]sinapyl alcohol was administered to excised shoots of E. ulmoides, ¹⁴C was incorporated into free SGSE and SGSE glucosides. In stems, incorporation into (+)-erythro-[¹⁴C]SGSE (0.037%) with 9.1% enantiomeric excess (% e.e.) was found; incorporation into the threo isomer was not detectable. Erythro-[¹⁴C]SGSE glucosides (0.047%) dominated over threo forms (0.007%) with 74.0% diastereomeric excess (% d.e.); both diastereomers were levorotatory with 32.0% e.e. and 18.3% e.e., respectively. In leaves, higher incorporation into (−)-erythro-[¹⁴C]SGSE (0.500%, 15.9% e.e.) than into the threo isomer (0.206%, 7.4% e.e.) was observed (41.6% d.e.). (−)-Erythro-[¹⁴C]SGSE glucosides (1.692%, 25.0% e.e.) were produced at higher rates than threo isomers (0.177%, 16.4% e.e.) with 81.0% d.e. In incubations of a mixture of [8-¹⁴C]sinapyl and [8-¹⁴C]coniferyl alcohols with an insoluble enzyme preparation from stems of E. ulmoides, erythro-SGSE was preferentially produced. The highest % d.e. (82.8) was observed at 60 min with the (+)-erythro isomer (21.4% e.e.) and the (−)-threo form (4.3% e.e.).Part of this report was presented at the 52nd Annual Meeting of the Japan Wood Research Society, Gifu, April 2002, and the 47th Lignin Symposium, Fukuoka, October 2002     

Stereochemistry and biosynthesis of 8-O-4′ neolignans in Eucommia ulmoides: diastereoselective formation of guaiacylglycerol-8-O-4′-(sinapyl alcohol) ether

Stereochemistry and biosynthesis of guaiacylglycerol-8-O-4′-(sinapyl alcohol) ether (GGSE), an 8-O-4′ neolignan, which consists of coniferyl and sinapyl alcohol moieties, in Eucommia ulmoides were investigated. Four 8-O-4′ neolignans, GGSE, syringylglycerol-8-O-4′-(coniferyl alcohol) ether (SGCE), guaiacylglycerol-8-O-4′-(coniferyl alcohol) ether (GGCE), and syringylglycerol-8-O-4′-(sinapyl alcohol) ether (SGSE), were synthesized. Their erythro and threo diastereomers were separated through acetonide derivatives, intermediates of the synthesis, and identified by means of nuclear magnetic resonance (NMR) spectroscopy. All of the erythro-acetonide derivatives have larger coupling constants (ca 9 Hz) for the C₇-H resonances than those of the threo ones (1.5–2 Hz). In the case of the four 8-O-4′ neolignans, the C₇-H coupling constants of the threo-isomers are not smaller than those of the erythro ones. GGSE isolated previously from this plant was identified as the erythro isomer by comparison of the ¹³C-NMR data with synthetic erythro-GGSE and threo-GGSE and the other 8-O-4′ neolignans mentioned as above. Administration of a mixture of [8-¹⁴C]coniferyl alcohol and [8-¹⁴C]sinapyl alcohol to excised shoots of E. ulmoides was carried out and the incorporation of ¹⁴C into erythro-[¹⁴C]GGSE was found to be higher than that in threo-[¹⁴C]GGSE. The occurrence of diastereoselective formation of erythro-GGSE by cross coupling of coniferyl and sinapyl alcohols is suggested.Part of this paper was presented at the 47th Lignin Symposium, Fukuoka, October 2002 and the 53rd Annual Meeting of the Japan Wood Research Society, Fukuoka, April 2003     

Inhibitory effects of selected Thai medicinal plants on Na+,K+-ATPase

Extracts of ten Thai indigenous medicinal plants having ethnomedical application in the treatment of dysuria were tested for their Na(+),K(+)-ATPase inhibitory activity. The hexane extracts of Cyperus rotundus and Orthosiphon aristatus showed high potent inhibitory activity on crude enzyme Na(+),K(+)-ATPase from rat brain.     

Appraisal of Thai glutinous rice husk for health promotion products

Rice husks of the RD 6 variety were refluxed with water for 30, 60 and 120 min. The longest extraction time resulted in the greatest yield (0.089 ± 0.008%), radical scavenging activity (IC₅₀ = 37.203 ± 0.421 μg/ml), and total phenolic and flavonoid contents (7.512 ± 0.008 g GAE/100 g extract and 36.886 ± 0.004 g QE/100 g extract). Fatty acids of cosmetic importance, such as hexanoic, heptatonic, octanoic, nonanoic, stearic, palmitic, oleic and linoleic acids, were quantified using the best antioxidant extract (166.004 mg/kg). The total phenolic content was related to the antioxidant activity and total fatty acid content (r = 0.997 and 0.864) in linoleic acid (r = 0.989), which displayed antioxidant properties (r = 0.996). The extract was non-cytotoxic in vero cells. Furthermore, it was compatible and stable in cosmetic formulations. Therefore, rice husks should be further studied for use in health promotion products.     

Dissection of gene loci underlying pasting temperature in cassava

In this study, a fine genetic map within the quantitative trait loci (QTL) underlying pasting temperature (PT) of cassava (Manihot esculenta Crantz) was constructed using newly developed simple sequence repeat (SSR) markers. The SSRs were designed on the basis of two scaffolds (S11341 and S4043) of the cassava genome, which covered previously identified QTL regions of the PT trait. A total of 55 and 61 SSR markers derived from S11341 and S4043, respectively, representing 0.29% of the cassava genome, were generated; of which 23 and 19 showed informative polymorphic patterns. Consequently, all identified informative polymorphic markers were used to genotype 200 F₁ progeny plants. The genotypic data were then analyzed, and the results showed that 480 markers were distributed across 23 linkage groups (LGs) with total length of 1,334 centimorgans (cM). An analysis of QTL underlying the PT trait revealed that marker EME81 on LG 1 had significant associations (P < 0.0001) in all environments evaluated. Four candidate genes were identified and selected for gene expression analysis in the parents, and among F₁ lines with high and low PT values. Significant differences were observed in relative expression of carbohydrate phosphorylase (CP) and starch synthase II (SSII) between high and low PT in 6-month-old cassava. We found CP and SSII genes to potentially control the PT trait. In addition, the marker EME81 was found to be a promising marker for specific PT trait selection in cassava populations, which should facilitate marker-assisted selection for desired PT traits.