Purification and Quantitative Analysis of Destruxins from Meterhizium anisopliae by HPLC

Abstract

Destruxins are metabolic toxins secreted from a fungus, Metarhizium anisopliae, during growth. The structure of destruxins has been identified as a cyclic hexadepsipeptide. Destruxins exhibit insecticidal activities. More than 35 different destruxins have been characterized to have a wide range of activity and specificity. In this report, an extraction solvent, acetonitrile, was found to yield high extraction efficiency. The fermentation broth was mixed with equal volume of acetonitrile and 5% NaCl, which formed two layers. The upper organic solvent layer, containing 80–95% of destruxins, was easily crystallized by lyophilization. The crystal could be redissolved with acetonitrile and separated by semi‐preparative HPLC. Each fraction was analyzed and identified with fast atom bombardment mass (FAB) spectrometry. The method for destruxin separation was optimized by adjusting the acetonitrile/water ratio in the gradient elution buffer of the semi‐preparative HPLC. Flatter gradient slopes may result in longer retention time and allow for higher quantity of separation. The quantitative analysis of destruxin could be achieved by generating a linear regression curve between concentrations vs. peak areas.