Cynanchum Tylophora alkaloids

Tylophorine (1) and its analogs, the phenanthroindolizidine alkaloids also referred to as tylophora alkaloids, have been isolated primarily from plants of the family Asclepiadaceae [13-16], Fig. (1), including members of the genus Tylophora, Vincetoxicum, Pergularia, Cynanchum, but also from Hypoestes verticillaris (Acanthaceae) [17], Cryptocarya phyllostemmon (Lauraceae) [18], Ficus hispida and F. septica (Moraceae) [2, 19]. TTie isolations of these alkaloids are summarized in Table 1. The most significant phenanthroindolizidine alkaloids are tylophorine (1), tylocrebrine (2), antofine (3), and tylophorinine (4), Fig. (2). 

Few alkaloids have been found in this relatively large family. Those in Cryptolepis, Cynanchum, Pergularia, Tylophora, and Vm-cetoxicum have been characterized, some have been synthesized, others have yet to be isolated in pure form. 

Cynanchum vincetoxicum (L.) Pers. contains traces of an alkaloid vincetene, which shows an interesting relationship to the phenanthroindolizidines found in Tylophora and other genera of the Asclepiadaceae. Spectroscopic study has shown vincetene to be the benzopyrroloisoquinoline derivative (2), and this structure has been confirmed by synthesis of the racemic dihydro-desoxy-deriva-tive (3).2... 

Staerk D, Lykkeberg AK, Christensen J, Budnik BA, Abe F, Jaroszewski JW (2002) In Vitro Cytotoxic Activity of Phenanthroindolizidine Alkaloids liom Cynanchum vincetaxicum and Tylophora tanakae Against Drug-Sensitive and Multidrug-Resistant Cancer Cells. J Nat Prod 65 1299... 

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