Cissus rheifolia

Phenanthroindolizidine and phenanthroquinolizidine alkaloids have similar pentacyclic structures however, the latter compounds contain a 6-membered piperidine E ring rather than the 5-membered pyrrolidine E ring found in the former compounds. Cryptopleurine (5), Fig. (2), is a representative and important phenanthroquinolizidine alkaloid. It is isolated primarily from Cryptocarya pleurosperma [20], but also from Cryptocarya laevigata [21], Boehmeria cylindrica [22, 23], Boehmeria platyphylla [24], Boehmeria caudate [21], and Cissus rheifolia [25], and is known as a highly toxic skin irritant and vesicant. 

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