Yellow pigments produced by oxidative oligomerization of dihydrochalcone glucoside and the reaction mechanism.

From the dried leaves of Lithocarpus polystachyus, yellow pigments, lithocarputins B (11) and C (12), were isolated with a colorless dihydrochalcone dimer, lithocarputin A (10). The pigments 11 and 12 are dimeric dihydrochalcone glycosides with bicyclo[3.2.

Ellagitannins and Oligomeric Proanthocyanidins of Three Polygonaceous Plants.

The aim of this study was to characterize hydrolyzable tannins in Polygonaceous plants, as only a few plants have previously been reported to contain ellagitannins. From , a new hydrolyzable tannin called persicarianin was isolated and characterized to be 3--galloyl-4,6-()-dehydrohexahydroxydiphenoyl-d-glucose. Interestingly, acid hydrolysis of this compound afforded ellagic acid, despite the absence of a hexahydroxydiphenoyl group.

Highly Oxidized Ellagitannins of and Their Oxidation-Reduction Disproportionation.

In the research on ellagitannin metabolism, two unique dehydroellagitannins, carpinins E () and F (), bearing dehydrohexahydroxydiphenoyl (DHHDP) and hydrated biscyclohexenetrione dicarboxyl ester (HBCHT) groups, were isolated from young leaves of . Upon heating in HO or treatment with pH 6 buffer at room temperature, and afforded the reduction product , isocarpinin A, with an ()-hexahydroxydiphenoyl (HHDP) group, suggesting the occurrence of redox disproportionation of the ()-DHHDP group. This was supported by the increase in production of in the pH 6 buffer solution by coexistence of epigallocatechin-3--gallate (), accompanied by oxidation of .

Crystal structure of a YeeE/YedE family protein engaged in thiosulfate uptake.

We have demonstrated that a bacterial membrane protein, YeeE, mediates thiosulfate uptake. Thiosulfate is used for cysteine synthesis in bacteria as an inorganic sulfur source in the global biological sulfur cycle. The crystal structure of YeeE at 2.