title: A pH-stability study of phoslactomycin B and analysis of the acid and base degradation products.
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 NPI 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 approximately 10 at 30 degrees C and 50 degrees 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 x 10(-PH) + kOH x 10(pH-14) (kH=45 +/- 7 M(-1) h (-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 alpha, beta-unsaturated lactone provided the major degradation product under base conditions. Two other products in which hydration of the alpha, beta-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.
authors.affiliation: ISBDD Suite 212B, Biotechnology Park, 800 East Leigh Street, Richmond, VA 23219, USA.
authors.forename: Suparna Das
authors.initials: SD
authors.lastname: Choudhuri
authors.forename: Sloan
authors.initials: S
authors.lastname: Ayers
authors.forename: William H
authors.initials: WH
authors.lastname: Soine
authors.forename: Kevin A
authors.initials: KA
authors.lastname: Reynolds
mesh_terms: D006863:Hydrogen-Ion Concentration; D007783:Lactones / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D009943:Organophosphorus Compounds / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D013302:Streptomyces / Q000235:genetics; D013696:Temperature
chemical_list: D007783:Lactones; D009943:Organophosphorus Compounds; C060449:phoslactomycin B; D010749:Phosphoprotein Phosphatases