Could it perhaps have been crossed wires from reading about another member of the Apocyanaceae? (dogbane) family?
Because this family of plants is absolutely replete with members which are extremely poisonous. A lot of them contain a white latex (in itself, NOT a good sign in a plant. Never eat or otherwise consume any parts of any plant which when cut or broken, exudes white latex, an awful bloody lot of such plants are very toxic, if not most of them, will be in some degree poisonous)
Apocyanaceae is a family in some respects comparable to the Euphorbiales, in that a great many of the species within genera of the family are
virulently poisonous. (and again with white latex being common, although AFAIK it is generally, unlike Euphorbia latexes, not irritant to corrosive, but simply chock full of toxic constituents.) And a family that one should never, ever consume a member of, unless you know exactly what you are doing and are certain too, that the species you intend to use, is indeed the species you think it to be.)
Some species in the family for example are used as arrow poisons. Such as those in the genus Akokanthera, many species within the genus having names such as 'poisonwood' 'round-leaved poison bush' and various variants including a descriptive epithet prefixed to 'poison tree', and they contain ouabain, a steroidal cardenolide type cardiac glycoside (I.e having action similar to digitalis, the heart medicine, and poison; which is derived from foxglove plants), that does the same kind of things as the poison from Oleanders, or the non-tryptamine-based fractions of the venom of many toads, although these are bufadienolides rather than cardenolides. The bufadienolides being cardiotoxic steroidal glycosides from animal sources, whilst all plants which produce cardiac glycosides produce those of the cardenolide type. Or at least, the bufadienolides are the sole preserve of the animal kingdom's cardiac steroids, with one notable exception, namely the sea squill, Scilla maritima, which is unique in that it produces the otherwise animal-derived bufadienolide type cardiac steroidal glycosides.
These cardiotoxic steroids slow the heart without diminishing, and IIRC indeed, increasing the force of it's beating, when used in medicinal doses as with digitalis, but in non-medical doses, stop the heart altogether. Akokanthera species as I mentioned, having found use in arrow poisons, particularly
ones which are used for poaching elephants. Which is a pretty good indicator, IMO, of quite how poisonous some of these plants can be to humans.
Plants belonging to the Apocyanaceae family need to be treated with the utmost caution, and to be regarded as highly poisonous until confirmed otherwise. Just like the genus Euphorbia. The wrong plant,and you are dead.
This has truly made my day.