Jeffrey B. Harborne

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.

A survey of antifungal compounds from higher plants, 1982–1993

Abstract Recent work on the characterization of antifungal metabolites in higher plants is reviewed. Interesting new structures are discussed and the distributi

Methods of Plant Analysis

The subject of phytochemistry, or plant chemistry, has developed in recent years as a distinct discipline, somewhere in between natural product organic chemistry and plant biochemistry and is closely related to both. It is concerned with the enormous variety of organic substances that are elaborated and accumulated by plants and deals with the chemical structures of these substances, their biosynthesis, turnover and metabolism, their natural distribution and their biological function.

The comparative biochemistry of phytoalexin induction in plants

Abstract Phytoalexin induction is now recognised as an important defence mechanism in plants against microbial infection. Earlier studies of this de novo resistance process indicated that a range of different secondary metabolites were produced, but that broadly speaking the type of phytoalexin produced was family specific. This has been borne out by more recent research, although several families have now been recorded as producing more than one class of phytoalexin. This review provides a comprehensive account of phytoalexin induction throughout the plant kingdom, with special attention to comparative aspects.

Flavonoids and the evolution of the angiosperms

Abstract Data on the distribution of flavonoids in the angiosperms are summarized and patterns of occurence are shown to be related to plant evolution. Different flavonoid types are regarded as primitive or advanced characters on the basis of biosynthetic complexity and on correlated frequencies of occurrence with morphological and anatomical features. The evolutionary significance of distribution patterns of proanthocyanidins, glycosylflavones, biflavonoids, 6- and 8-hydroxyflavonoids and anthocyanins is discussed in turn. The importance of these various distribution patterns is considered in relation to an ecological function for these flavonoids.

Chemosystematics of the umbelliferae— a general survey

Abstract Some 300 umbellifer species, representing 52 per cent of the genera of the family, have been surveyed for their leaf phenolics, using both fresh and herbarium tissue. The results show that, with few exceptions, species can be divided into two groups, those with flavone (usually luteolin) and those with flavonol (kaempferol and/or quercetin). These groupings are mainly of interest at the generic level but are also related to tribal divisions and may be of phylogenetic significance in the family. Other classes of flavonoid are rare: leucocyanidin was detected once in Apiastrum , and the glucoxanthone mangiferin once in Heptaptera . Furanocoumarins were found in the leaves mainly of Angelica, Peucedanum and Seseli species but a survey of seeds of 130 species showed that these compounds were widespread in the family, some correlation with tribal divisions being apparent. Examination of the Umbelliferae for presence of polyacetylenes, simple hydroxycoumarins and the rare sugars, apiose and umbelliferose, has shown that these substances are widespread and consequently of little systematic interest within the family. Soluble proteins and the enzymes peroxidase and esterase present in the seed of selected species from all tribes in the Apioideae were studied by acrylamide gel electrophoresis. Distinct differences in patterns were found to be present at the tribal and generic levels. In some cases, the macromolecular supported the micromolecular data in conforming generic separations. The general value of the various chemical characters in the systematics of the family is discussed.

The role of sesquiterpene lactones and phenolics in the chemical defence of the chicory plant

Abstract Amounts of the sesquiterpene lactones and the major phenolics were determined in the chicory plant at different times during the growing season. The levels of the sesquiterpene lactones (lactucin, lactupicrin and 8-deoxylactucin) and the hydroxycoumarin cichoriin were found to be highest in the most actively growing regions of the plant. In two-choice and no-choice feeding experiments with borosilicate discs, 8-deoxylactucin, lactupicrin and cichoriin significantly reduced feeding of Schistocerca gregaria at levels comparable to those present in the plant. Cichoriin was still significantly antifeedant at 0.006% dry wt, while aesculin, aesculetin and the caffeic acid ester, chicoric acid were inactive. We conclude that the three sesquiterpene lactones secreted in the latex provide a significant barrier to herbivory in chicory, although the phenolics and notably cichoriin also protect the plant from insect feeding.

Comparative biochemistry of flavonoids-III. : A correlation between chemistry and plant geography in the genus Eucryphia☆

Abstract A correlation between flavonoid chemistry and plant geography has been discovered among Eucryphia species. The rare quercetin 5-monomethyl- and 3,5-dimethyl ethers, azaleatin and caryatin, have been identified in leaf of the two South American species E. cordifolia and E. glutinosa and in two of their hybrids. Caryatin occurs in the free state but azaleatin is present as the 3-galactoside, as a 3-arabinosylgalactoside and as a 3-diglucoside; the 3-galactoside, 3-rhamnoside and a 3-diglycoside of quercetin are also present. Neither of the above methyl ethers occurs in leaf of the other three known Eucryphia species, all of which are of Australian origin. These three species have a much simpler flavonoid pattern: E. milliganii has dihydroquercetin glycoside, E. moorei a quercetin 3-triglycoside and E. lucida kaempferol 3,7-dimethyl ether as the respective major leaf constituents. This survey represents a complete coverage of the Eucryphiaceae as at present constituted and the bearing of these results on the taxonomic position of the family are discussed.

Fungitoxic dihydrofuranoisoflavones and related compounds in white lupin, Lupinus albus☆

Abstract Chromatographic investigation of a methanolic extract of white lupin roots has revealed the presence of six new dihydrofuranoisoflavones (lupinisoflavones A-F). Three monoprenylated (3,3-dimethylallyl-substituted) isoflavones (wighteone, luteone and licoisoflavone A), two diprenylated isoflavones [6,3′-di(3,3-dimethylallyl)genistein (lupalbigenin) and 6,3′-di(3,3-dimethylallyl)-2′-hydroxygenistein (2′-hydroxylupalbigenin)] and two pyranoisoflavones (parvisoflavone B and licoisoflavone B) have also been isolated from the same source. In addition to genistein, leaf extracts of L. italbus contain 3′-O-methylorobol which is presumed to be the precursor of lupisoflavone [5,7,4′-trihydroxy-3′-methoxy-6-(3,3-dimethylallyl)isoflavone]. Probable biogenetic relationships between the prenylated, and dihydrofurano-and pyrano-substituted isoflavones in roots and leaves of L. albus are briefly discussed.

Biochemistry of plant phenolics.

Kurt Hostettmann: Recent advances in methodology for the isolation and purification of plant phenolics C.F. Van Sumere & K. Vande Casteele: Reversed Phase-HPLC analysis of flavonoids and the biochemical identification of cultivars of evergreen Azalea H. Geiger: The identification of phenolic compounds by colour reactions Gerhard Schilling: Recent advances in NMR-spectroscopy of plant phenolics H.-R. Shulten: Recent advances in soft ionization mass spectrometry and its applications to plant phenolics M.J.C. Rhodes: The physiological significance of plant phenolic compounds Geza Hrazdina & George J. Wagner: Compartmentation of plant phenolic compounds: sites of synthesis and accumulation Alain M. Boudet, Annick Graziana & Raoul Ranjeva: Recent advances in the regulation of the prearomatic pathway B. Monties: Recent advances on lignin inhomogeneity H. Grisebach: Topics in flavonoid biosynthesis Dervilla M.X. Donnelly: Neoflavanoids David G. Roux & Daneel Ferreira: Rationalization of divergent condensation sequences in flavanoid oligomerization Edwin Haslam: New polyphenols for old Tannins Stewart A. Brown: Recent advances in the biosynthesis of coumarins G.H.N. Towers & E. Yamamoto: Interactions of cinnamic acid and its derivatives with light R.H. Thomson: Recent advances in the chemistry and biochemistry of quinones W. Barz, J. K stner, K.-M. Weltring & D. Strack: Recent advances in the metabolism and degradation of phenolic compounds in plants and animals V.S. Butt: Oxygenation and oxidation in the metabolism of aromatic compounds John Friend: Phenolic substances and plant disease Jeffrey B. Harborne: Phenolics and plant defence H. Wagner: New plant phenolics of pharmaceutical interest W.S. Pierpoint: Phenolics in food and feedstuffs: the pleasures and perils of vegetarianism Tony Swain: Plant phenolics: past and future.