Occurrence and distribution of free flavonoid aglycones in plants

Most reports on the identification of known flavonoids in new plant sources as well as those on novel flavonoids naturally deal with the two most abundant classes, the flavones and flavonols. For this chapter we have listed all references to the occurrence of flavone and flavonol aglycones which have appeared from 1975 to 1980, and also include such earlier references as were overlooked in the relevant chapters of The Flavonoids’ (1975). Emphasis is given to the natural distribution of these compounds. The data are collected in Tables 4.1 and 4.2 which cite substances, plant sources and references. Since 1974, some 50 flavones and 60 flavonols with common substitution patterns have been described as novel compounds. Many are simply new methyl ethers of known compounds. The structures are arranged throughout the Tables by number and arrangement of substituents in ring A, followed by ring B. Wherever possible, the plant organs from which the compounds have been isolated are cited. In cases where authors have extracted the ‘whole plant’ or ‘aerial parts’, it does not necessarily follow that the compound is present in all parts, since these substances are often specifically located in certain organs only. In all cases where free aglycones are encountered, especially highly methylated flavonoids, it is likely that they occur externally, or are associated with secretory structures and are correlated with the production of other lipophilic secondary compounds, mainly of terpenoid origin.

Flavones and Flavonols

Evaluation of the protective potential of Ambrosia maritima extract on acetaminophen-induced liver damage

The world around us has been shaped by evolution. In social terms, evolutionary processes seem fast. The changes which have taken place in the organization of human societies over the last 1000 or even 100 years are indeed enormous and have had, and will continue to have, important ecological and evolutionary consequences for ourselves and other living organisms. But in biological terms change is very slow. It has taken two million years for man to evolve from the tool-using Australopithecus, and placental mammals had been evolving for well on 100 million years before even the first of the higher primates arose nearly 35 million years ago (Stebbins, 1966; McAlester, 1968). And when it is remembered that the biochemical differences between ourselves and modern day representatives of these early primates are extremely small, e.g. one or two amino acid differences in the structure of a few proteins (Dayhoff, 1969), or a few minor changes in excretory patterns (Smith, 1968), it is obvious that biochemical evolution is even slower still. It seems likely, therefore, that we will only be able to determine striking changes in biochemical evolution by looking at the differences between many major diverse taxa. Unfortunately, such data are scarce.

Evolution of Flavonoid Compounds

The interrelationships within theHeliantheae s. lato and the closely relatedEupatorieae are analyzed and discussed. The basis to this discussion is a cladistic analysis of 141 morphological characters (172 apomorphic states) scored for 97 genera. TheHeleniae s. lato, a subgroup of theHeliantheae s. lato, are paraphyletic, and a monophyletic group corresponding largely to theHeliantheae s. str. is recognized. TheEcliptinae sensuRobinson are polyphyletic. TheCoreopsidinae form an ingroup in theHeliantheae s. str. TheTageteae (Pectidinae) and theMadieae (Madiinae) are two separate branches within the helenioid assemblage of taxa.

J. Averett

Papers

6-Methoxyapigenin from thirty-four species of compositae