Proteaceae plants, tropane alkaloids

The tropane alkaloids occur mainly in the plant family Solanaceae but are also found in the families Convolvufaceae, Erythroxylaceae, Proteaceae, and Rhizophoraceae. In addition, the presence of tropane alkaloids has occasionally been indicated in the families Euphorbiaceae and Cruciferae (cf. Tables II and III). For a detailed account of the distribution of tropane alkaloids among species, interested readers should consult Refs. (15-23) and references therein. 

Tropane alkaloids mainly occur in the Solanaceae family but are also found in other families such as Convolvulaceae, Erythroxylaceae, Proteaceae and Rhizophoraceae. Less frequently, tropane alkaloids have been mentioned in the Euphorbiaceae, Brassicaceae and Olacaceae families which show no taxonomic relationships with Solanaceae. In several species of Erythroxylum, the tropane alkaloids are characterized by a 3 3-hydroxy function and a carboxyl group at C-2 of the tropane nucleus. The most famous representant of this group is cocaine (Fig. 2). In Table 1 the distribution of tropane alkaloids in the plant kingdom is indicated. 

Tropane alkaloids are common in the Solanaceae, but are found in several other plant families. Tropane alkaloids are found in the tribes Cestreae, Datureae, Nicandreae, Salpig-lossideae, and Solaneae (Evans, 1979). These alkaloids also are found in the Convolvulaceae, which most systematists consider to be related closely to the Solanaceae (Waterman and Gray, 1987). Other families that contain tropane alkaloids are the Brassicaceae Cochlearia), Dioscoreaceae, Elaeocarpaceae, Erythroxylaceae, Euphorbiaceae Phyllan-thus), Orchidaceae, Proteaceae, and Rhizophoraceae (Dahl-gren et al, 1981 Romeike, 1978 Waterman and Gray, 1987 Wooley, 1993). Because other types of alkaloids are found in several of these families, many reports should be confirmed (Romeike, 1978). 

Occurrence in Non-solanaceous/Non-convolvulaceous Taxa. Beside the Erythroxylaceae, tropane bases were detected in further plant families which are again not closely related with the Solanaceae [Brassicaceae, Euphorbiaceae, Proteaceae, Rhizophoraceae (Waterman 1998)]. Eor details on the occurrence and distribution of different types of tropane alkaloids inside the two Solanales family in comparison with the unrelated families mentioned above outside this order see Table 3.7. 

Tropane alkaloids (TAs), a class of specialized metabolites with a bicyclic tropane ring in their structures, include clinically important hyoscyamine and scopolamine, the stimulant and narcotic cocaine, and the nortropane alkaloids calystegines. Plants producing TAs are distributed, sometime sporadically, across separate angiosperm families (e.g., Proteaceae, Convolvulaceae, Brassicaceae, Euphorbiaceae, Rhizophoraceae, Solanaceae, and Erythroxylaceae) (Griffin and Lin 2000). Studies of TA biosynthesis have been performed predominantly in Solanaceae plants, and thus little is known regarding TA pathways in other families. 

---