Release of hydrogen cyanide via a post-secretion Schotten-Baumann reaction in defensive fluids of polydesmoid millipedes.

Mandelonitrile benzoate, a minor defense component produced by polydesmoid millipedes, is produced in large amounts together with hydrogen cyanide following shake-disturbances administered to individuals of Nedyopus tambanus tambanus, Parafontaria tonominea, Epanerchodus sp., and Epanerchodus fulvus. These species commonly produce mandelonitrile and benzoyl cyanide (the oxidized product after discharge). The newly generated mandelonitrile benzoate was identified as a product of post secretion Schotten-Baumann reaction under basic conditions of bled bodily fluids (pH ca. 9.0), and was not an enzymatic reaction product. The reaction occurred in vitro even under less basic conditions [1M Tris-HCl buffer (pH 8.0)], and could be defined as a new mechanism of hydrogen cyanide release occurring in roughly half of polydesmoid millipedes. Species possessing no benzoyl cyanide, such as Oxidus gracilis and Cryptocorypha sp., could also produce mandelonitrile benzoate under conditions in which benzoyl cyanide was exogenously provided.