Development of a Sensitive High-Performance Liquid Chromatography-Diode Array Detection Assay for the Detection and Quantification of the Beauveria Metabolite Oosporein from Submerged Culture Broth and Bio-Control Formulations

A sensitive high-performance liquid chromatography-diode array detection (HPLC-DAD) assay is described for the detection and quantification of the Beauveria metabolite oosporein from fungal culture broth and two biocontrol agent formulations. In all cases, analyte recovery was achieved with a Britton-Robinson buffer system at pH 5.5 diluted with methanol 3:7 (v/v) (BR5.5-MeOH). The HPLC-DAD assay, using a binary solvent gradient with acidic modifiers and detecting the metabolite at 287 nm, showed linearity over 3 orders of magnitude and a limit of detection (LOD) of 6.0 +/- 2.3 microg of oosporein/L of BR5.5-MeOH. The oosporein content of the representative fungal culture broth samples and two Beauveria formulations (Melocont-Pilzgerste and Melocont-WP) was found to be 504.7 +/-13.6 mg of oosporein/L of culture filtrate, 7.4 +/- 0.6 mg of oosporein/kg of Melocont-Pilzgerste, and 38.2 +/- 1.3 mg of oosporein/kg of Melocont-WP with recovery rates of 93 +/- 2, 99 +/- 8, and 92 +/- 3%, respectively.