In this study, we evaluated the stereoselective bioactivity of four propiconazole stereoisomers against the causal agents of the banana leaf spot disease (Curvularia lunata and Colletotrichum musae). We also evaluated the stereoselective degradation of the stereoisomers in banana leaves under field test conditions. The Superchiral S-OX column successfully separated the four propiconazole stereoisomers. X-ray single-crystal diffraction confirmed that the absolute configuration of the cis-stereoisomer-(+)-A of propiconazole was (2R,4S)-propiconazole and that of the cis-stereoisomer-(-)-A of propiconazole was (2S,4R)-propiconazole. In vitro antibacterial results revealed that (2R,4S)-(+)-propiconazole had the highest activity against the two target plant fungi. In this study, a new and efficient high-performance liquid chromatography tandem mass spectrometry method was developed for the determination of the four stereoisomeric residues of propiconazole in banana leaves. The mean recoveries of the method for the stereoisomers were 76.3-103% with relative standard deviations of 1.25-11.4%. The four propiconazole stereoisomers had a detection limit of 0.002-0.006 mg/kg and a limit of quantification of 0.02-0.03 mg/kg in banana leaves. Propiconazole-(-)-B and propiconazole-(-)-A degraded slightly faster than their corresponding enantiomers propiconazole-(+)-B and propiconazole-(+)-A in banana leaves collected from three typical banana production areas.
Keywords: HPLC−MS/MS; absolute configuration; banana leaves; bioactivity; propiconazole stereoisomers; stereoselective degradation.