Ponceau 3R is an azo dye that once was used as a red food colorant. Ponceau 3R is carcinogenic in rats following its oral administration, producing liver-cell tumours. It also produced bladder tumours in mice following its implantation in the urinary bladder. The oral study in mice was considered inadequate for evaluation. Ponceau 3R was reduced in vitro by Fusobacterium sp. 2, a human intestinal anaerobe, to a product which is mutagenic when metabolically activated by liver S9 preparations in the Salmonella/mammalian-microsome mutagenicity test. This mutagenic metabolite has been identified as 2,4,5-trimethylaniline.

Coniine is a neurotoxic piperidine alkaloid found in poison hemlock (Conium maculatum L.). Coniine which is considered to be racemic mixture first described by Gieseke in 1827; von Hoffman confirmed the structure in 1881; Ladenburg perfermed synthesis in 1886. Coniine enantiomers are nicotinic acetylcholine receptor (nAChR) agonists. The relative potencies of these enantiomers on TE-671 cells expressing human fetal nicotinic neuromuscular receptors had the rank order of (-)-coniine > (+/-)-coniine > (+)-coniine. The rank order potency in SH-SY5Y cells which predominately express autonomic nAChRs was: (-)-coniine>(+)-coniine> (+/-)-coniine.