A pH-stability study of phoslactomycin B and analysis of the acid and base degradation products.
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.
Choudhuri
Suparna Das
SD
ISBDD Suite 212B, Biotechnology Park, 800 East Leigh Street, Richmond, VA 23219, USA.
Ayers
Sloan
S
Soine
William H
WH
Reynolds
Kevin A
KA
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
D007783:Lactones; D009943:Organophosphorus Compounds; C060449:phoslactomycin B; D010749:Phosphoprotein Phosphatases