Purification and Characterization of a Novel (R)-Mandelonitrile Lyase from the Fern Phlebodium aureum

Using high-performance liquid chromatography and nuclear magnetic resonance we identified vicianin as the cyanogenic compound of Phlebodium aureum. The (R)-hydroxynitrile lyase involved during cyanogenesis in the catabolism of the aglycon ([R]-mandelonitrile) was purified to apparent homogeneity. The purified holoenzyme is a homomultimer with subunits of Mr = 20,000. At least three isoforms of the enzyme exist. In contrast to other hydroxynitrile lyases, mandelonitrile lyase (MDL) from P. aureum was not inhibited by sulfhydryl- or hydroxyl-modifying reagents, suggesting a different catalytic mechanism. The enzyme is active over a broad temperature range, with maximum activity between 35 and 50[deg]C, and a pH optimum at 6.5. In contrast to (R)-MDLs isolated from several species of the Rosaceae family, (R)-MDL from P. aureum is not a flavoprotein. The substrate specificity was investigated using immobilized enzyme and diisopropyl ether as solvent. The addition of cyanide to aromatic and heterocyclic carbonyls is catalyzed by this (R)-MDL, whereas aliphatic carbonyls are poorly converted.     

Flavonoids of Datura

Four analogues of quercetin and of kaempferol are found in Datura. The occurrence of these compounds vary throughout the examined populations, but do not seem correlated with the estimated UV-B exposure environment of their collection sites.     

Flavonoids of geigeria

Chromatographic separation of the ethanol extract of Geigeria burkei resulted in the isolation and characterization of two known flavonoids, 5,7,3′,4′-tetrahydroxy-6-methoxyflavone and 5,7,4'-trihydroxy-6 methoxyflavone. ¹³CNMR data, as well as the respiratory inhibition and uncoupling of oxidative phosphorylation, is reported for the first time.     

Flavonoids of Onychium lucidum

从栗柄金粉蕨(Onychium lucidum)地上部分的甲醇抽提物中分到10个成分,经详细的一维、二维核磁数据分析,它们被鉴定为木犀草甙(1),3,7-二甲基槲皮素(2),高山甙B(3),金粉蕨素(4),栗柄醇(5),金粉蕨醇B(6),β-谷甾醇(7),胡萝卜甙(8),齐墩果酸(9)和蔗糖(10)。栗柄醇系新成分。1,2,9系首次由金粉蕨属分到。     

Microbial Transformation of Flavonoids

The ability of a number of fungal spores, and in particular of resting vegetative mycelia, to transform naringin and naringenin was studied. In general, only hydrolytic cleavage of the sugar moieties of naringin to produce prunin and naringenin was observed. Two cultures, Penicillium charlesii and Helminthosporium sativum, also produced two unidentified flavonoid compounds but in very low yields. No transformation of aglycone was detected, although the compound was metabolized by some cultures when supplied as the glycoside prunin. A fluorodensitometric method was developed for the quantitative analysis of flavonoid compounds.     

Flavonoids of Chromolaena odorata

A dichloromethane extract of Chromolaena odorata has yielded 2′-hydroxy-3,4,4′,5′,6′-pentamethoxychalcone, 2′,4-dihydroxy-4′,5′,6′-     

Flavonoids of Aster subulatus

We report here from Aster subulatus, flavone and flavonol aglycones, monoglycosides and a diglycoside of kaempferol as well as chlorogenic acid.     

Flavonoids of Brickellia vernicosa

Thirteen 6-methoxy-flavonoids and four flavanones were isolated from Brickellia vernicosa. This is the first isolation of flavanones from a member of Brickellia and of the previously unreported 3-rhamnoside of 6-methoxykaempferol.     

Flavonoids of Elaeocarpus lanceofolius

4′-Methylmyricetin has been isolated from the leaves of Elaeocarpus lanceofolius together with myricetin and its 3-O-rhamnoside. This is the second report of the natural occurrence of a 4′-methyl ether of myricetin and the first in the family, Elaeocarpaceae.     

Flavonoids of gaura triangulata

Ten flavonoids were obtained from Gaura triangulata including luteolin and luteolin 7-glycoside derivatives which are atypical for the family Onagraceae. Apigenin-based C-glycosylflavones, previously reported from the Onagraceae in the monogeneric tribe Circaeeae, have also been identified. The flavonoid profile of G. triangulata is distinctive for the family since previous studies of the Onagraceae reported primarily flavonols.     

小叶三点金的黄酮类成分研究

从小叶三点金(Desmodium microphyllum)乙醇溶液中分离得到9个黄酮类化合物,通过波谱学方法分别鉴定为()-表儿茶素(1)、genistein-4′-O-β-glucoside(2)、异荭草苷(isoorientin,3)、荭草苷(orientin,4)、木犀草素(luteotin,5)、异日本獐牙菜素(isoswertiajaponin,6)、luteoayamenin(7)、木犀草素-7-O-β-D-葡萄糖苷(luteolin-7-galactoside,8)、木犀草素-7-O-鼠李糖苷(luteolin-7-rhamnoside,9)。所有化合物均为首次在该植物中分离得到。     

Flavonoids of iphiona scabra

Thirteen flavonoids were isolated from the aerial parts of Iphiona scabra: the 3-sulphate, 3,4′-disulphate and 3,7,4′-trisulphate of isorhamnetin; the 3,7-disulphate and 3,7,4′-trisulphate of quercetin; and the 7-sulphate of hispidulin; the 3-glucosides and 3-galactosides of isorhamnetin and quercetin; and artemetin, salvigenin and 5-hydroxy-3,6,4′-tetramethoxyflavone.