Phytochemistry of Acacia—sensu lato
Little is known about the chemistry of most species of the genus Acacia, although the genus is quite large and widespread in the warm subarid and arid portions of the world. As presently defined, Acacia is a cosmopolitan genus containing in excess of 1350 species. Taxonomic relationships and identification of Acacia species are difficult; new studies of the genus confirm that Acacia is an agglomeration of at least five discrete groups. The major elements of this ‘genus’ are the groups now recognized as the subgenus Acacia, the genus Faidherbia, the subgenus ‘Aculeiferum’, relatives of Acaciacoulteri, Bentham’s series Filicinae, the subgenus Phyllodineae, and possibly others, each with somewhat distinct chemistry. A number of secondary metabolites have been reported from various Acacia species including amines and alkaloids, cyanogenic glycosides, cyclitols, fatty acids and seed oils, fluoroacetate, gums, non-protein amino acids, terpenes (including essential oils, diterpenes, phytosterol and triterpene genins and saponins), hydrolyzable tannins, flavonoids and condensed tannins. The most evident and best known are polysaccharides (gums) and complex phenolic substances (condensed tannins).