Chiral Inversion Studies of Denopamine by HPLC with a β-Cyclodextrin Derivative Immobilized Chiral Column

Chiral inversion of denopamine (DP, R (-)-form), which is an optically active and an orally administrable cardiotonic agent, was investigated by HPLC with a β-cyclodextrin (β-CD) derivative immobilized chiral column. Enantiomers of DP were successfully separated with a resolution of 2.4 within 10 min under the reversed-phase mode by ULTRON ES-PhCD column, where a perphenylated β-CD derivative was immobilized. Using this chiral HPLC method validated, chiral inversion studies of DP drug substance, DP in tablets and its changed forms (powders and suspensions) under the various stress conditions were performed. As a result, chiral inversion of DP was observed in an aqueous solution state of DP drug substance and suspensions of DP tablets under the heat stress conditions. On the other hand, DP drug substance, DP tablets and its changed forms were stable for heat stress and UV irradiation in the solid state. S (+)-form of DP as a heat degradation product was identified by LC-MS/MS analysis through comparing retention times in chiral HPLC, UV spectra obtained by a photo diode array detector and MS and MS/MS spectra with those of the authentic substance.