Bufonid toad

The apparent occurrence of decahydroquinolines as major alkaloids in dendrobatid frogs of the genera Dendrobates, Epipedobates, and Phyllobates, and in bufonid toads of the genus Melanophryniscus, strongly suggests the independent evolutionary development of biosynthetic pathways to decahydroquinolines in two separate amphibian lineages. 

Fig. 9. Structures of homopumiliotoxins from dendrobatid frogs and bufonid toads. The structure of homopumiliotoxin 223G is based on nuclear magnetic resonance spectral analysis (77). The absolute configuration is unknown. Homopumiliotoxin 223G occurs in dendrobatids (77), ranids (73), and bufonids (8 ), while the other alkaloids have been detected only in the bufonid toads (Melanophryniscus) (81).

Disubstituted pyrrolizidines occur in bufonid toads of the genus Mela-nophryniscus, where in M. stelzneri, (5Z,8 )-223H, (5Z,8 )-223B, (5 .8 )-223B, and other pyrrolizidines were detected as minor constituents (81). 

The occurrence of quinolizidines in skin extracts from dendrobatid frogs has been suspected for some time (5), but only recently have sufficient mass and FTIR spectral data been obtained to permit assignment of structures to quinolizidines from dendrobatid and ranid frogs and bufonid toads. As yet, none of these quinolizidines has been isolated in quantities sufficient for nuclear magnetic resonance spectral characterization. 

Over 30 amphibian alkaloids from dendrobatid frogs, bufonid toads, or ranid frogs now are assigned to the 1,4-disubstituted quinolizidine class. For many of these, FTIR data are not yet available. Thus, structural and stereochemical assignments to this class, and the proposed 4,10Z configuration, should be considered tentative for many of these alkaloids. A 4,6-disubstituted quinolizidine class, considered likely by analogy to the... 

E. CigHjgN, —, 168 C,/n/z 235(3), 152(100), 110(15). OD. Hj derivative, mh 237, 152. Structure a 4-hexenyl-1-methylquinolizidine. An isomer (235E ) from a bufonid toad has an interior double bond in the six-carbon side chain (57). Infrared data on 235E (81). 

Precoccinelline (193C) and related tricyclic alkaloids have been detected only rarely in dendrobatid frogs and bufonid toads. Precoccinelline is a minor alkaloid in one Central American population of Dendrobates aura-tus 31), but it was a major alkaloid in an introduced population of D. 

Morphine (XXIII), a well-known plant alkaloid, has been detected in trace amounts in the skin of the bufonid toad, Bufo marinus (184). It is possible that this, and perhaps other trace alkaloids found in amphibian... 

Daly JV, Wilham JM, Spande TF, Garaffo HM, Gil RR, Silva GL, et al. Alkaloids in bufonid toads (Melanophryniscus) temporal and geographic determinants for two Argentinian species. J Chem Ecol 2007 33(4) 871-87. 

Figure 43 Alkaloids from bufonid toads of the genus Melanophryniscus pumiliotoxin 265D (1734) pumiliotoxin 309A (1735) pumiliotoxin 307G (1736) putative structure for alkaloid 207S (1737) quinolizidine 2751 (1738) alkaloid 249F (1739) indolizidine 223D (1740).

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