Abiesin,a biflavonoid of abies webbiana

Abiesin, a new biflavonoid, has been isolated from the leaves of Abies webbiana and identified as 5,3″,7″- trihydroxy-7,4′,4?-trimethoxy-(3′,6″)-biflavone.     

Xanthones from Tovomita pyrifolium

The wood of Tovomita pyrifolium (Guttiferae) contains the novel tovopyrifolins A [1,6-dihydroxy-7-methoxy-5-prenyl-6′,6′-dimethylpyrano (2′,3′:3,2)xanthone], B (1,5-dihydroxy-3,4-dimethoxyxanthone) and C (1,3,5-trihydroxy-2-methoxyxanthone) and also the known tovophyllins A and B [structure revised to 1,6-dihydroxy-5-prenyl-6′, 6′-dimethylpyrano(2′,3′:3,2)-6″,6″-dimethylpyrano(2″,3″:7,8)xanthone].     

A pyrano-isoflavone from seeds of Milletia thonningii

Extraction of the seeds of Milletia thonningii gave alpinumisoflavone, its monomethyl and dimethyl derivatives, robustic acid and a new pyrano-isoflavone. The structure of the latter was established by chemical transformation and spectroscopic means.     

Dihydrochalcones from lindera umbellata

Two dihydrochalcones, 2′,6′-dihydroxy-4′-methoxydihydrochalcone and 2,4′,6′-trihydroxydihydrochalcone have been isolated from leaves of Lindera umbellata.     

青蕨植物化学成分的研究

从青蕨根部的乙酸乙酯提取物中分离得到4个化合物。通过化学及波谱分析鉴定其结构为：saucerneol D(1),dehydrogoniothalamin(2),1-acetoxyl-2-piperonyl-6-[6-methoxyl-piperonyl]3,7-dioxabicyclo-[3,3,0]-octane(3) and 5,5′-dihydroxy-3-methoxy-6,8,3″,3″-tetramethylpyran-(3′,4′)flavone-7-O-[β—D—apiofuranosyl-(1→6)]-β-D-glucopyranoside(4)。其中化合物(4)为新化合物,化合物(1)为首次从该属植物中分离得到。     

Flavonoids of the citrus cultivar calamondin and synthetic 2′β-dihydroxychalcones

Eight methoxyflavones were isolated and identified from the peel of calamondin. Citromitin and 5-O-desmethylcitromitin are actually nobiletin and 5-O-desmethylnobiletin, respectively. 5,6,7,8,3′,4′-Hexamethoxyflavanone and 5-hydroxy-6,7,8,3′,4′-pentamethoxyflavanone are not constituents of calamondin, although previously reported.     

C-glycosylflavones from Oryza sativa

Eight flavone C-glycosides isolated from rice plant were found to act as probing stimulants for planthoppers. They have been identified as the known compounds schaftoside, neoschaftoside, carlinoside, isoorientin 2″-glucoside and the new constituents neocarlinoside (6-C-β-D-glucopyranosyl-8-C-β-L-arabinopyranosylluteolin), isoscoparin 2″-glucoside (chrysoeriol 6-C-β-D-(2-O-β-D-glucopyranosyl)glucopyranoside) and its 6?-p-coumaric and ferulic acid esters.     

Magnetic resonance studies of the interaction of divalent metal cations with 2,3-bisphosphoglycerate

The binding of Mg²⁺ to intracellular 2,3-bisphosphoglycerate in the human red blood cell is significant to the function of the cell. We have studied interactions of Mg²⁺ and Mn²⁺ with 2,3-bisphosphoglycerate by magnetic resonance spectroscopy. The results of this study reveal the presence of two independent divalent metal cation binding sites of similar affinity (K_D = 3.0 ± 0.5 mM) in the 2,3-bisphosphoglycerate molecule, one on each phosphoryl group, contrary to the assumption of one metal ion binding site made in the previous literature. Over the range of their intracellular concentrations, ATP and ADP, however, possess only one metal ion site in spite of the presence of multiple phosphoryl groups. These results are consistent with the chemistry of metal-chelation which requires the formation of 5- or 6-membered rings for the stability of chelate structures.     

C-Glycosylflavones from Avena sativa

Avena sativa leaves, stems and inflorescences contain a range of new C-glycosylflavone 2″-O-glycosides, including vitexin and isoswertisin 2″-rhamnosides, isovitexin and isoorientin 2″-arabinosides. The structure of ‘vitexin 4′-rhamnoside’ from Crataegus oxyacantha is revised in vitexin 2″-rhamnoside.     

Two new C-methylated flavonoids from Myrica gale

From the leaves of Myrica gale 2′,4′-dihydroxy-6′-methoxy-3′,5′-dimethylchalcone has been isolated. The fruits yielded 2′-hydroxy-4′,6′-dimethoxy-3′-methyldihydrochalcone. The constitutions were deduced from spectroscopic data and confirmed by synthesis.     

Geminate recombination in carboxy hemoglobin A and its relation to overall carbon monoxide reactivity

The geminate recombination of CO with carboxy hemoglobin (Hb₄(CO)₃) following a ten nanosecond laser pulse and the overall combination of the fourth CO with Hb₄(CO)₃ has been studied as a function of pH in the presence and absence of inositol hexaphosphate. The results indicate that the kinetics of both reactions are independent of pH and phosphate concentration. The results are discussed in terms of a two-step mechanism: a pre-equilibrium step followed by heme—ligand bond formation. The latter is also known as the geminate recombination reaction (Hb + CO α Hb · CO α HbCO).