It is the major object of this review to present the presently known naturally occurring terpenoids and aromatic compounds of the Hepaticae. Furthermore, the biological activity of the isolated compounds and chemosystematics of the Hepaticae are summarized.

Chemical Constituents of Hepaticae

Chemical Constituents of the Hepaticae

The present chapter is the first compilation in which the flavonoid chemistry of all lower plants has been brought together in a comprehensive manner. In a chapter of this size it is not possible to be exhaustive in a historical sense, and reference to early work is only made when such work is considered to be of continuing significance. Nevertheless this summary attempts to establish a reasonably complete database representing work published prior to early 1986 and upon which future updates can be based. The emphasis throughout is on published work in which flavonoid structures have been defined. Thus some extensive surveys in which (for example) only presence or absence data appear are not fully represented. Discussion is focused primarily on the distribution of flavonoids and the possible phylogenetic significance (if evident) of this distribution. Limited space precludes all but passing comment on the myriad of taxonomic implications addressed in the literature.

Distribution of flavonoids in the lower plants and its evolutionary significance

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.

J.E. Averett

Papers

Acacetin 7-O-rhamnosyl-galacturonide from Reboulia hemispherica