Occurrence in the Solanaceae

Our knowledge of the occurrence and distribution of alkaloids in this family is generally based on (i) traditional isolation and structure elucidation procedures and (ii) different chromatographic methods, predominantly TLC. 

Quantitative information concerning simple pyrrolidine alkaloids is rather rare. The roots of Nicandra physalodes contained 0.1% hygrine whereas five Physalis spp. contained considerably less (Romeike 1965a,b). The content of the epigeal parts of N. physalodes was even extremely low. Surprisingly, cuscohygrine turned out to be the main alkaloid of Datura discolor roots with a concentration of 0.06% which amounts to 20% of the total alkaloid content (0.31%). This is in contrast with other Datura spp. where tropanes (hyoscyamine/scopolamine) represent the principal alkaloids (Evans and Somanabandhu 1974a). 

Chemotaxonomic Relevance. The existing data for an intrafamilial evaluation of this topic are full of gaps in case of the Solanaceae (Table 3.1). However, since simple pyrrolidines are plesiomorphic characters shared with the well-studied Convolvulaceae (Table 3.2) and at least the occurrence and distribution of cuscohygrine is also well-documented in the Solanaceae, it might be that there is a similar tendency in both Solanales families. 

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Occurrence in the Solanaceae. p-Coumaric acid, caffeic acid, methyl caffeate, and methyl ferulate as well as certain of their 2,3-dihydro derivatives have been identified as constituents of the leaves of Cestrum parqui L Herit. with good phytotoxic activity against different species (D Abrosca et al. 2004). Family-specific phenylpropanoid acids like tropic acid or 2-hydroxytropic acid as acyl moieties of tropane alkaloids are synthesized via phenylalanine -> phenylpyruvic acid (l )-3-phenyllactic acid (Fig. 3.14 Table 3.1 (T5-T7-B)]. Tropic acid may occur as a metabolite of, e.g., hyoscyamine, but the free acid is not synthesized as such (for details see Sect. 3.4). 

Occurrence in the Solanaceae. In contrast to the corresponding HCA their reduced derivatives as well as HCA esters show volatile properties. For a number of these metabolites see Sect. 6.3.4. 

Occurrence in the Solanaceae. Phenylacetic acid is integrated as an acyl moiety into the structure of certain ester type tropane alkaloids (Table 3.1 (T7-C)). 

Occurrence in the Solanaceae. As already mentioned above, mono-acylated HCA conjugates of putrescine were detected as constituents of Solanum lycoper-sicum sub nom. Lycopersicum esculentum, Nicotiana tabacum, and Petunia x hybrida (Martin-Tanguy et al. 1978) ... 

Non-solanaceous Occurrence. Withanolides have been discovered also in certain Tacca spp. of the Taccaceae (taccalonolides Huang et al. 2002) and Ajuga spp., e.g., A. parviflora Benth., Lamiaceae (ajugins Khan et al. 1999) as well as in some marine organism. Nevertheless, their occurrence in the Solanaceae is predominating by far. 

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