Resin glycosides from Ipomoea wolcottiana as modulators of the multidrug resistance phenotype in vitro.

Abstract Recycling liquid chromatography was used for the isolation and purification of resin glycosides from the CHCl 3 -soluble extracts prepared using flowers of Ipomoea wolcottiana Rose var. wolcottiana . Bioassay-guided fractionation, using modulation of both antibiotic activity against multidrug-resistant strains of Gram-negative bacteria and vinblastine susceptibility in breast carcinoma cells, was used to isolate the active glycolipids as modulators of the multidrug resistance phenotype. An ester-type dimer, wolcottine I, one tetra- and three pentasaccharides, wolcottinosides I–IV, in addition to the known intrapilosin VII, were characterized by NMR spectroscopy and mass spectrometry. In vitro assays established that none of these metabolites displayed antibacterial activity (MIC > 512 μg/mL) against multidrug-resistant strains of Escherichia coli , and two nosocomial pathogens: Salmonella enterica serovar Typhi and Shigella flexneri ; however, when tested (25 μg/mL) in combination with tetracycline, kanamycin or chloramphenicol, they exerted a potentiation effect of the antibiotic susceptibility up to eightfold (64 μg/mL from 512 μg/mL). It was also determined that these non-cytotoxic (CI 50  > 8.68 μM) agents modulated vinblastine susceptibility at 25 μg/mL in MFC-7/Vin + cells with a reversal factor (RF MCF-7/Vin + ) of 2–130 fold.