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Biomedical subjects

J B Harborne

Publications and source records attributed to J B Harborne.

15 recordsLinked to original sources
PubMed2001

A distinctive flavonoid chemistry for the anomalous genus Biebersteinia.

Leaf surface extracts of Biebersteinia orphanidis have yielded a complex mixture of five flavones with the unusual 5,7-dihydroxy-6,8-dimethoxy A ring substitution pattern. They are acerosin, hymenoxin, nevadensin, sudachitin and 5,7,4'-trihydroxy-6,8-dimethoxyflavone. Also present at the leaf surface are gardenin B, luteolin, apigenin, acacetin and the coumarin umbelliferone. The internal leaf flavonoids include the 7-glucosides of apigenin, luteolin and tricetin, together with the 7-rutinosides of apigenin and luteolin. This profile differs from those of B. heterostemon and B. odora. It appears that B. orphanidis is as highly distinctive in its flavonoid pattern as it is phytogeographically. The data also confirm the conclusion of other studies, including rbcL and atpB gene sequence analysis, that Biebersteinia is completely unrelated to the Geraniaceae, where it was once placed.

Flavonoids↗
PubMed2001

Acacetin glycosides as taxonomic markers in Calamintha and Micromeria.

A new acetylated flavone glycoside, acacetin 7-O-[6""-O-acetylglucosyl(1""-->2")]rhamnosyl(1"'-->6")glucoside, has been isolated from the leaves of Calamintha glandulosa together with the known compound acacetin 7-O-rhamnosyl(1"'-->6")glucoside. The occurrence of these flavonoids in the closely related genera Satureja, Micromeria, Acinos and Clinopodium indicates that their distribution may be of taxonomic significance.

Biomarkers↗
PubMed2000

Advances in flavonoid research since 1992.

Some of the recent advances in flavonoid research are reviewed. The role of anthocyanins and flavones in providing stable blue flower colours in the angiosperms is outlined. The contribution of leaf flavonoids to UV-B protection in plants is critically discussed. Advances in understanding the part played by flavonoids in warding off microbial infection and protecting plants from herbivory are described. The biological properties of flavonoids are considered in an evaluation of the medicinal and nutritional values of these compounds.

Animals↗
PubMed1999

The flavonoids of Tanacetum parthenium and T. vulgare and their anti-inflammatory properties.

The lipophilic flavonoids in leaf and flower of Tanacetum parthenium and T. vulgaris have been compared. While those of T. parthenium are methyl ethers of the flavonols 6-hydroxykaempferol and quercetagetin, the surface flavonoids of T. vulgare are methyl ethers of the flavones scutellarein and 6-hydroxyluteolin. Apigenin and two flavone glucuronides are surprisingly present in glandular trichomes on the lower epidermis of the ray florets of T. parthenium. The opportunity has been taken to revise the structures of the four 6-hydroxyflavonol methyl ethers of T. parthenium based on NMR measurements. These are now shown to be uniformly 6- rather than 7-O-methylated. Tanetin, previously thought to be a new structure, is now formulated as the known 6-hydroxykaempferol 3,6,4'-trimethyl ether. The vacuolar flavonoids of both plants are dominated by the presence of apigenin and luteolin 7-glucuronides; nine other glycosides were present, including the uncommon 6-hydroxyluteolin 7-glucoside in T. vulgare. When the major flavonol and flavone methyl ethers of the two plants were tested pharmacologically, they variously inhibited the major pathways of arachidonate metabolism in leukocytes. There were significant differences in potency, with the tansy 6-hydroxyflavones less active than the feverfew 6-hydroxyflavonols as inhibitors of cyclo-oxygenase and 5-lipoxygenase.

Animals↗
PubMed1997

Chrysin and other leaf exudate flavonoids in the genus Pelargonium.

In a chemotaxonomic survey of 57 Pelargonium species, leaf exudate flavonoids were detected in 35% of the sample, mostly in trace amounts. However, chrysin and a related C-methylflavanone were identified as major leaf surface constituents of P. crispum, and a mixture of quercetin and kaempferol mono-, and di- and trimethyl ethers of P. quercifolium. In two other species, P. fulgidum and P. exstipulatum, methylated flavones were the only lipophilic flavonoids present. This is the first report of leaf surface flavonoids from the genus Pelargonium.

Chromatography, High Pressure Liquid↗
PubMed1995

A biologically active lipophilic flavonol from Tanacetum parthenium.

A new lipophilic flavonol, 6-hydroxykaempferol 3,7,4'-trimethyl ether, called tanetin, has been characterized in the leaf, flower and seed of feverfew, Tanacetum parthenium. It co-occurs with the known 6-hydroxykaempferol 3,7-dimethyl ether, quercetagetin 3,7-dimethyl ether and quercetagetin 3,7,3'-trimethyl ether. Pharmacological tests indicate that tanetin could contribute to the anti-inflammatory properties of feverfew by inhibiting the generation of pro-inflammatory eicosanoids, although it is unlikely to be the only biologically active compound within the plant. Water soluble flavone glycosides were detected in the leaves and identified as apigenin 7-glucuronide, luteolin 7-glucuronide, luteolin 7-glucoside and chrysoeriol 7-glucuronide.

Chromatography, High Pressure Liquid↗
PubMed1994

Methylated C-glycosylflavones as taxonomic markers in orchids of the subtribe Ornithocephalinae.

In a leaf flavonoid survey of 15 Brazilian orchid species from the subtribe Ornithocephalinae, flavone C-glycosides were found to be the major constituents in all except two Ornithocephalus taxa. In Zygostates cornuta a rare glycoside, apigenin 7,4'-dimethyl ether 6-C-glucoside-2"-O-rhamnoside, was identified. This also occurred in Z. alleniana, Z. lunata, Z. pellucida and Z. pustulata. Two further similar apigenin 7,4'-dimethyl ether C-glycoside-O-rhamnosides, possibly with different C-linked sugars, were detected in Z. multiflora and Z. grandiflora. In Z. cornuta, apigenin 4'-methyl ether 6-C-glucoside-2"-O-rhamnoside was found to co-occur with the apigenin 7,4'-dimethyl ether derivative. Ornithocephalus myrticola was distinguished by the presence of an apigenin 8-C-methylpentoside and three apigenin 7-methyl ether 8-C-glycoside derivatives. In O. bicornis and O. kruegeri, another apigenin 7,4'-dimethyl ether C-glycoside was found, while from Phymatidum falcifolium, apigenin 7,4'-dimethyl ether and apigenin 7-methyl ether C-glycosides and their O-arabinosides were isolated. Chytroglossa marileoniae also contained an apigenin 7,4'-dimethyl ether C-glycoside, which appeared to be the same as that in P. falcifolium. Rauhiella silvana, on the other hand, could be distinguished from all the other taxa studied by the absence of methylated C-glycosylflavones and presence of isovitexin. 6-Hydroxyflavone O-glycosides, which are characteristic leaf constituents of some Oncidium species in the related subtribe Oncidinae were not detected in the present sample.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbohydrate Sequence↗
PubMed1990

Role of secondary metabolites in chemical defence mechanisms in plants.

The classic view that secondary constituents are waste products in plants has been replaced by one in which their value is assumed to be as a protection against herbivorous and microbial attack. However, secondary pathways may still be physiologically important as a means of channelling and storing carbon compounds, accumulated from photosynthesis, during periods when nitrogen is limiting or whenever leaf growth is curtailed. Large increases in the amount of secondary metabolites can occur in stressed plants and those subject to mechanical damage or that caused by insects. In order to establish a protective role for a given metabolite, it is necessary to monitor concentrations over the life cycle of the plant, to survey plant populations, to determine specific localization within tissues and to carry out bioassays against insects and microorganisms. Synergy between toxins of the same class or of different classes is likely. Changes in secondary chemistry may also occur during ontogeny, and protection may be restricted to the most vulnerable plant organs. Finally, toxins may vary indiscriminately in their distribution within the plant or within populations and still provide protection.

Hormones↗