Isolation and characterisation of an aryl-β-D-glucoside uptake and utilisation system ( abg ) from the gram-positive ruminal Clostridium species C. longisporum

A phosphotransferase-dependent aryl-β-glucoside uptake and utilisation system (abg) was isolated from the ruminal Clostridium (“C. longisporum”). The system is composed of three genes, abgG, abgF and abgA, and a number of regulatory regions, including terminator/antiterminator type stem-loop structures preceding the abgG and abgF genes. Similarity analysis of the proteins encoded by these genes indicated that they were responsible for the regulation of the abg system through antitermination (AbgG), the uptake and phosphorylation of aryl-β-glucosides (AbgF) and the hydrolysis of the intracellular phosphorylated glycosides (AbgA). Experimental evidence for the functions of AbgF and AbgA was obtained. Although it was not possible to demonstrate any function for AbgG, a promoter 5′ to the abgG gene was identified which was responsible for expression of the downstream genes. The abg system is remarkably similar to operons from the gram negative Enterobacteriaceae, both in the coding and non-coding regulatory regions. Received: 3 April 1997 / Accepted: 8 September 1997     

Two new flavone glycosides from Cirsium lineare

An examination of four species of Cirsium disclosed the presence of two new flavonoids in C. lineare. The structure of one was 5,4′-dihydroxy-6,7,3′-trimethoxyflavone (cirsilineol) 4′-monoglucoside and the other 5,3′,4′-trihydroxy-6,7-dimethoxyflavone (cirsiliol) 4′-monoglucoside. Luteolin 7-glucoside was found in C. suffultum, and pectolinarin and linarin in C. kamtschaticum and C. pectinellum.     

Phenolics of five yam (dioscorea) species

Cyanidin-3-glucoside, (+)-catechin and the procyanidin dimers ‘B-1’ and ‘B-3’ were identified as phenolic constituents of Dioscorea alata tubers, and strong evidence for the presence of a procyanidin trimer and a tetramer was found. The quantity of (+)-catechin and relative proportions of the procyanidin dimers were determined in 10 cultivars of five of the main edible yam species.     

管花马兜铃化学成分的研究

从管花马兜铃中分得马兜铃酸-A,7-甲氧基马兜铃酸-A,马兜铃内酰胺-β-D-葡萄糖甙,尿囊素和Eupomatenoid-7。     

Two new neoflavonoids and C-glycosylflavones from Passiflora serratodigitata

The aerial parts of Passiflora serratodigitata yielded 5,7-dihydroxy-4-phenylcoumarin, its 7-β-glucoside and the known C-glycosylflavones 2″-xylosylvitexin, 2″-xylosylisovitexin, vitexin, isovitexin, a vicenin, and orientin. The known flavone chrysin was also isolated. This is the first report of neoflavonoids in the family Passifloraceae.     

The systematic implications of the complexity of leaf flavonoids in the bromeliaceae

In a leaf survey of 61 species of the Bromeliaceae, an unexpectedly wide spectrum of flavonoid constituents was encountered. The family is unique amongst the monocotyledons in the frequency and variety of flavonoids with extra hydroxylation or methoxylation at the 6-position. More common flavonols (in 43% of species) and flavones (in 13%) are distributed throughout the family whereas the rarer flavonoid classes are restricted to one or two of the three subfamilies. Thus 6-hydroxyflavones were found in both the Pitcairnioideae (in 50%) and the Tillandsioideae (in 14%) but patuletin (in 19%), gossypetin (in 1 species) and methylated 6-hydroxymyricetin derivatives (in 24%) were detected only in the Tillandsioideae. A new flavonol, 6,3′,5′-trimethoxy-3,5,7-4′-tetrahydroxyflavone, was identified as the 3-glucoside in Tillandsia usneoides and a new glycoside, patuletin 3-rhamnoside, in Vriesea regina. Myricetin glycosides were found only in the Bromelioideae and their presence here and the concomitant absence of 6-hydroxyflavonoids could indicate the primitive condition of this subfamily. The flavonoid results, in toto, confirm the view based on morphology, that the Bromeliaceae occupies an isolated position in relation to other monocot families.     

Biosystematics of the monocotyledoneae—flavonoid patterns in leaves of the liliaceae

In a leaf survey of 168 species of the Liliaceae, most of the major flavonoid classes were found to be represented in the family. Flavonols occurred most frequently: quercetin and kaempferol were detected in 40% and 42% of the sample respectively, while the flavones luteolin and apigenin were present in only 24% and 20% of the sample. Methylated derivatives, i.e. isorhamnetin, diosmetin and tricin were rare. Procyanidins were present in 17 species, flavonoid sulphates in only one species and flavone C-glycosides in only three species. Anthraquinone pigments were identified in species of Aloe Asphodeline and Asphodelus. Three new flavonoid glycosides were characterised during the course of the survey: diosmetin 7-diglucoside in Colchicum byzanthinum and tricin 7-fructosylglucoside and tricin 7-rutinoside-4′-glucoside in Hyacinthus orientalis cv. ‘Quean of the Pinks’. On the basis of the flavonoid survey, the subfamilies of the Liliaceae may be grouped into those containing flavonols only, those with flavones only or those having both flavonols and flavones. Members of the related families: Amaryllidaceae (17 species), Agavaceae (1 species) and Xanthorrhoeaceae (1 species) contained only flavonols. The subfamilies Scilloideae, Asphodeloideae and Melanthioideae show the most chemical variation whilst the Wurmbaeoideae and Lilioideae are the most homogeneous groups. The tribe Scilleae is unusual in that both flavone- and flavonol-containing genera occur and a wide variety of flavonoid types are represented. A comparison of the leaf flavonoids of the Liliaceae with those found in families related to the grasses showed that all except two classes of flavonoid compound (5-methylated flavones and 5-deoxyflavonoids) found in the Juncaceae. Cyperaceae, Palmae and Gramineae are present in the Liliaceae thus supporting the view that all four families could have arisen from Liliaceae-like ancestors.     

Flavonoids from Erythroxylon argentinum

Quercetin 3-rutinoside, quercetin 3-α-l-rhamnoside, 7,4′-dimethylquercetin 3-rutinoside and the novel glycoside 7,4′-dimethylquercetin 3-rutinoside-5-glucoside have been identified from aerial parts of Erythroxylon argentinum.