Arecaidine has tumorgenicity.

5-Hydroxymethyl-2-furancarboxylic acid (Sumiki's acid) is a naturally occurring human metabolite. Sumiki's acid was first identified in the urine of a leukemia patient who was excreting an abnormal amount of its glycine derivative. Sumiki's acid has been found to be a byproduct of the fungus Aspergillus and probably other species of fungi and yeast as well.

Oxytocin free acid (9-Deamidooxytocin) is an analog of oxytocin in which the glycinamide residue at position 9 in oxytocin has been replaced by a glycine residue. Oxytocin is a pleiotropic, peptide hormone with broad implications for general health, adaptation, development, reproduction, and social behavior.