Thevetia thevetioides Cardenolide and Related Cardiac Glycoside Profile in Mature and Immature Seeds by High-Resolution Thin-Layer Chromatography (HPTLC) and Quadrupole Time of Flight-Tandem Mass Spectrometry (Q-TOF MS/MS) Reveals Insights of the Cardenolide Biosynthetic Pathway.

Thevetia thevetioides is a species within the Apocynaceae family known for containing cardenolide-glycosides, commonly referred to as cardiac glycosides, which are characteristic of this genus. The seeds of the Thevetia species are frequently used as a model source for studying cardiac steroids, as these glycosides can be more readily extracted from the oil-rich seeds than from the plant's green tissues. In this work, the cardenolide profile of ripe and immature seeds was determined and compared to establish the main differences. Ripe seeds contain six related cardenolides and triosides, with thevetin B being the predominant component. In contrast, immature seeds exhibit a total of thirteen cardiac glycosides, including monoglycosides such as neriifolin and peruvosides A, B, and C, as well as diglycosides like thevebiosides A, B, and C. Some of these compounds have previously been identified as degradation products of more complex cardiac glycosides; however, their presence in immature seeds, as described in this study, suggests that they may serve as biosynthetic precursors to the triosides observed in mature seeds. The glycoside patterns observed via HPTLC are associated with specific chemical structures characteristic of this genus, typically featuring thevetose or acetyl-thevetose at the first position, followed by glucose or gentibiose in di- or trisaccharides, independent of the trioside aglycones identified: digitoxigenin, cannogenin, or yccotligenin. Ripe seeds predominantly contain triosides, including thevetin B, C, and A, the latter of which has not been previously reported.