Abstract
Phoslactomycin B (PLM-B), a potent and selective inhibitor of serine threonine phosphatase is of interest for its antitumor, antifungal and antiviral activity. Described herein is an evaluation of the solution stability of phoslactomycin B at various pH and temperature conditions. Phoslactomycin B was produced from a NP1 mutant strain of Streptomyces sp. HK-803 and purified by semi-preparative HPLC. A study of PLM-B degradation was carried out in the pH range of 2∼10 at 30°C and 50°C using an HPLC assay. The PLM-B decomposition was observed to exhibit a U-shaped pH profile and demonstrated both acid and base-catalyzed decomposition. The decomposition could be described by the equation kOBS=kH×10−pH+kOH×10pH−14 (kH=45±7 M−1h−1; kOH=448±73 M−1h−1). PLM-B was found to be most stable at pH 6.63. The major acid and base products were separated and purified. Mass spectroscopic and NMR analysis revealed hydrolysis of the α,β-unsaturated lactone provided the major degradation product under base conditions. Two other products in which hydration of the α,β-unsaturated double bond preceded hydrolysis or methanolysis of the lactone were obtained. Under acidic condition MS and NMR analysis revealed that a dehydration step provided a C9-C11 phosphorinane derivative of PLM-B as one of the major products. The remaining acid degradation products were shown to be mixture of various dehydration products containing an additional double bond in central core of the PLM-B carbon skeleton. The major acid and base degradation products had dramatically reduced antifungal activity despite retaining the same structural core.
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Choudhuri, S., Ayers, S., Soine, W. et al. A pH-Stability Study of Phoslactomycin B and Analysis of the Acid and Base Degradation Products. J Antibiot 58, 573–582 (2005). https://doi.org/10.1038/ja.2005.78
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DOI: https://doi.org/10.1038/ja.2005.78
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