ABSTRACT
Bioassay-guided fractionation of an aqueous methanolic extract of Dioscorea bulbifera L. bulbs was performed using organic solvents. A novel plasmid-curing compound was identified as 8-epidiosbulbin E acetate (EEA) (norditerpene) on the basis of modern spectroscopic analysis and X-ray crystallography. EEA exhibited broad-spectrum plasmid-curing activity against multidrug-resistant (MDR) bacteria, including vancomycin-resistant enterococci. EEA cured antibiotic resistance plasmids (R-plasmids) from clinical isolates of Enterococcus faecalis, Escherichia coli, Shigella sonnei and Pseudomonas aeruginosa with 12-48% curing efficiency. The reference plasmids of Bacillus subtilis (pUB110), E. coli (RP4), P. aeruginosa (RIP64) and Salmonella typhi (R136) were cured with efficiency ranging from 16% to 64%. EEA-mediated R-plasmid curing decreased the minimal inhibitory concentration of antibiotics against MDR bacteria, thus making antibiotic treatment more effective. The antibiotic resistance pattern revealed that the compound was effective in the reversal of bacterial resistance to various antibiotics. In addition, the compound did not show any cytotoxicity against a broad range of human cancer cell lines, namely MCF-7 (breast cancer), SiHa (cervical cancer) and A431 (epidermal carcinoma), and hence has the potential to be used as a lead compound for drug discovery programmes.
Subject(s)
Anti-Bacterial Agents/pharmacology , Dioscorea/chemistry , Diterpenes/pharmacology , Drug Resistance, Multiple, Bacterial/drug effects , Plasmids/drug effects , Anti-Bacterial Agents/biosynthesis , Antineoplastic Agents, Phytogenic/pharmacology , Cell Line, Tumor , DNA, Bacterial/drug effects , DNA, Bacterial/genetics , Diterpenes/metabolism , Drug Screening Assays, Antitumor , Humans , Hydrogen-Ion Concentration , Magnetic Resonance Spectroscopy , Microbial Sensitivity Tests , Molecular Conformation , Plant Extracts/chemistry , Plant Roots/chemistry , X-Ray DiffractionABSTRACT
Callus formation was achieved with root, hypocotyl, and cotyledon explants of niger (Guizotia abyssinica Cass.) cultivar Sahyadri on Murashige and Skoog medium containing 0.5 mg l-1 ß-indoleacetic acid + 1.5 mg l-1 6-benzylaminopurine (BAP). Hypocotyl and cotyledon-derived calli when transferred onto a medium with 0.5 mg l-1 BAP produced an average of 12-32 shoots/ callus culture. The callus retained its potential for shoot regeneration for more than 19 months. The shoots formed an extensive root system and were transferred to pots kept in a greenhouse, where the survival rate was 98%. The plantlets flowered in vitro if transfer to fresh medium or to soil was delayed by 40-50 days. All regenerants were diploid with 2n=30.
