ABSTRACT
Bioassay-directed fractionation for Staphylococcus aureus multidrug resistance efflux pump inhibitors resulted in isolation of novel acylated neohesperidosides from Geranium caespitosum. The more highly acylated compounds had no direct activity against S. aureus, but potentiated activity of the antibiotics berberine, rhein, ciprofloxacin and norfloxacin. Cellular concentrations of berberine were greatly increased in the presence of active esters.
Subject(s)
Anti-Bacterial Agents/isolation & purification , Anti-Bacterial Agents/pharmacology , Drug Resistance, Multiple, Bacterial , Geranium/chemistry , Hesperidin/analogs & derivatives , Hesperidin/pharmacology , Membrane Transport Modulators , Membrane Transport Proteins/antagonists & inhibitors , Acylation , Anti-Bacterial Agents/chemistry , Bacillus megaterium/drug effects , Bacillus megaterium/growth & development , Bacillus megaterium/metabolism , Bacillus subtilis/drug effects , Bacillus subtilis/growth & development , Bacillus subtilis/metabolism , Hesperidin/isolation & purification , Microbial Sensitivity Tests , Nuclear Magnetic Resonance, Biomolecular , Staphylococcus aureus/drug effects , Staphylococcus aureus/growth & development , Staphylococcus aureus/metabolismABSTRACT
In addition to accumulating biologically active chemicals, plant roots continuously produce and secrete compounds into their immediate rhizosphere. However, the mechanisms that drive and regulate root secretion of secondary metabolites are not fully understood. To enlighten two neglected areas of root biology, root secretion and secondary metabolism, an in vitro system implementing root-specific elicitation over a 48-day time course was developed. After roots of Arabidopsis thaliana had been elicited with salicylic acid, jasmonic acid, chitosan, and two fungal cell wall elicitors, the secondary metabolites subsequently secreted were profiled. High-performance liquid chromatography was used to metabolically profile compounds in the root exudates, and 289 possible secondary metabolites were quantified. The chemical structures of 10 compounds were further characterized by (1)H and (13)C NMR: butanoic acid, trans-cinnamic acid, o-coumaric acid, p-coumaric acid, ferulic acid, p-hydroxybenzamide, methyl p-hydroxybenzoate, 3-indolepropanoic acid, syringic acid, and vanillic acid. Several of these compounds exhibited a wide range of antimicrobial activity against both soil-borne bacteria and fungi at the concentration detected in the root exudates.
Subject(s)
Arabidopsis , Plant Extracts/analysis , Plant Roots/metabolism , Anti-Bacterial Agents/analysis , Anti-Bacterial Agents/pharmacology , Antifungal Agents/analysis , Antifungal Agents/pharmacology , Chromatography, High Pressure Liquid/methods , Magnetic Resonance Spectroscopy/methods , Plant Extracts/pharmacologyABSTRACT
Root fluorescence is a phenomenon in which roots of seedlings fluoresce when irradiated with ultraviolet (UV) light. Soybean (Glycine max) and rye grass (Elymus glaucus) are the only plant species that have been reported to exhibit this occurrence in germinating seedling roots. The trait has been useful as a marker in genetic, tissue culture and diversity studies, and has facilitated selection of plants for breeding purposes. However, the biological significance of this occurrence in plants and other organisms is unknown. Here we report that the Andean tuber crop species Oxalis tuberosa, known as oca in the highlands of South America, secretes a fluorescent compound as part of its root exudates. The main fluorescent compounds were characterized as harmine (7-methoxy-1-methyl-beta-carboline) and harmaline (3, 4-dihydroharmine). We also detected endogenous root fluorescence in other plant species, including Arabidopsis thaliana and Phytolacca americana, a possible indication that this phenomenon is widespread within the plant kingdom.
