A "flavone-polysaccharide" redefined as a mixture of 6-methoxyluteolin penta- and hexa-O-glycosides.

The incomplete structure proposed in 1972 for a unique "flavone-polysaccharide" compound, MF-1, from the liverwort Monoclea forsteri, has been re-examined. Rather than the proposed 8-methoxyluteolin structure with polysaccharides attached to the 7- and 4'-hydroxyls, MF-1 has been shown to be primarily a mixture of penta- and hexa-O-glycosides of 6-methoxyluteolin, which are accompanied by their luteolin analogues. MS and NMR evidence is marshalled to define the structure of MF-la as 6-methoxyluteolin 7-O-[2-O-alpha-rhamnosyl-3-O-alpha-arabinosyl-beta-glucuronide]-4'-O-[2-O-alpha-rhamnosyl-3-O-beta-xylosyl-beta-glucuronide], and MF-1b as 6-methoxyluteolin 7-O-[2-O-alpha-rhamnosyl-beta-glucuronide]-4'-O-[2-O-alpha-rhamnosyl-3-O-beta-xylosyl-beta-glucuronide].

The fluorescence and photostabilities of naturally occurring isoflavones.

The 5,7-dihydroxyisoflavones do not emit detectable fluorescence and are significantly more photostable than the two 7-hydroxy-5-deoxyisoflavones, daidzein and formononetin. The latter isoflavones emit fluorescence that depends on the basicity of the solution and the polarity of the solvent. Comparison of the spectral distributions of the emission in methanol in the presence and absence of base indicates that it originates from the conjugate anion excited singlet states.

The mis-identification of the major antioxidant flavonoids in young barley (Hordeum vulgare) leaves.

Several papers have appeared in the literature since 1992 which refer to a major "isoflavonoid" antioxidant in young green barley leaves (Hordeum vulgare) as 2''-O-glucosylisovitexin. In the present paper the original NMR data supporting this structural assignment are examined and found to have been misinterpreted. HPLC and NMR data are used to prove that the major flavonoid antioxidants in young green barley leaves are in fact the flavone-C-glycosides, saponarin and lutonarin.

Age-induced diminution of free radical scavenging capacity in bee pollens and the contribution of constituent flavonoids.

Bee-collected pollen ("bee pollen") is promoted as a health food with a wide range of nutritional and therapeutic properties. The objective of the current study is to evaluate the contribution made through the free radical scavenging capability of bee-collected floval pollens by their flavonoid/phenolics constituents, and to determine whether this capability is affected by aging. The free radical scavenging effectiveness of a bee pollen (EC(50)) as measured by the DPPH method is shown to be determined by the nature and levels of the constituent floral pollens, which can be assayed via their phenolics profiles by HPLC.

The unique occurrence of the flavone aglycone tricetin in Myrtaceae pollen.

In pollen, flavonoids are usually found as glycosides and in particular, flavonol 3-O-diglycosides. However, in members of the Myrtaceae, subfamily Leptospermoideae, the rare flavone aglycone tricetin, along with other flavonoid aglycones including 3-O-methyl quercetin and luteolin, have been found to comprise a significant portion of the constituent flavonoids.

Flavonoid gene expression and UV photoprotection in transgenic and mutant Petunia leaves.

The effects of UVB radiation on plant growth rate, gene expression and flavonoid content in wild-type, and in transgenic and mutant F3'H deficient Petunia lines have been studied for the first time. In wild-type Petunia, UVB induced an increase in total levels of flavonols and this was due to an up-regulation of several genes in the phenylpropanoid pathway. Furthermore, UVB induced a higher rate of production of dihydroxylated flavonols than mono-hydroxylated equivalents.

Antioxidant capacities of green and cyanic leaves in the sun species, Quintinia serrata.

Anthocyanins scavenge harmful reactive oxygen species (ROS), and may provide antioxidative protection within plant cells. For the shade species Elatostema rugosum A. Cunn.