In this paper, we report the dose-dependent antioxidant activity and DNA protective effects of zingerone. At 500 μg/mL, the DPPH radical scavenging activity of zingerone and ascorbic acid as a standard was found to be 86.7 and 94.2 % respectively. At the same concentration, zingerone also showed significant reducing power (absorbance 0.471) compared to that of ascorbic acid (absorbance 0.394). The in vitro toxicity of stannous chloride (SnCl2) was evaluated using genomic and plasmid DNA. SnCl2-induced degradation of genomic DNA was found to occur at a concentration of 0.8 mM onwards with complete degradation at 1.02 mM and above. In the case of plasmid DNA, conversion of supercoiled DNA into the open circular form indicative of DNA nicking activity was observed at a concentration of 0.2 mM onwards; complete conversion was observed at a concentration of 1.02 mM and above. Zingerone was found to confer protection against SnCl2-induced oxidative damage to genomic and plasmid DNA at concentrations of 500 and 750 μg/mL onwards, respectively. This protective effect was further confirmed in the presence of UV/H2O2-a known reactive oxygen species (ROS) generating system-wherein protection by zingerone against ROS-mediated DNA damage was observed at a concentration of 250 μg/mL onwards in a dose-dependent manner. This study clearly indicated the in vitro DNA protective property of zingerone against SnCl2-induced, ROS-mediated DNA damage.

Zerumbone, a natural cyclic sesquiterpene, has been the focus of recent research as it has been found to exhibit selective toxicity towards cancer cells compared to normal cells. Studies on the cell cycle phase-specific effects of this interesting compound, however, remain sparse. Hence, concentration and time-dependent effects of zerumbone were evaluated employing a suitable model system, the naturally synchronous surface cultures of Physarum polycephalum. Zerumbone treatment in S, early, and late G2 phases resulted in G2 arrest. Early G2 phase exhibited the highest sensitivity (P < 0.001) to the compound. Protein profiles showed a complete inhibition of cyclin B1 expression following zerumbone treatment. Furthermore, FACS and comet analysis revealed that zerumbone inhibited DNA synthesis (P < 0.001) without being genotoxic at the concentrations tested. Differential display of mRNA showed distinct zerumbone-induced variations in transcript profiles, an analysis of which suggested a likely link between cellular networks involving stress-related gene expression and G2 arrest in P. polycephalum.

Background & objectives:β-lactamases play a predominant role in drug-resistance amongst Enterobacteriaceae. Presence of genes on transferable plasmids encoding these enzymes favours their dissemination across species and genera within and outside geographical boundaries. This study was aimed to understand the presence of β-lactamases and transferable plasmids in clinical isolates of Klebsiella spp. which can contribute to the spread of resistance determinants.Methods:A total of 41 clinical isolates of Klebsiella spp., collected from a tertiary care centre in Kerala, India, were checked for antibiotic sensitivity and the presence of plasmids. The ability to produce extended-spectrum β-lactamases (ESBLs) and metallo-β-lactamases (MBLs) was screened for and confirmed in 29 plasmid-harbouring isolates. blaNDM-1-specific primers were used for polymerase chain reaction amplification with plasmid DNA as template to determine episomal prevalence of this gene and its sequence-based phylogeny employing similar sequences from GenBank. Plasmid replicon typing was also carried out to determine the presence of transferable plasmids.Results:Our results showed a high degree of multidrug-resistant (MDR) pathogens with ESBL production confirmed in 52 per cent, MBL in 31 per cent and co-production of both enzymes in seven per cent of the plasmid-bearing isolates. Plasmid DNA from 14 per cent of the isolates produced blaNDM-1-specific amplicons which showed sequence homology with those from bacteria of different genera and geographical areas. The predominant replicon type was found to be that of conjugative plasmids belonging to the incompatibility group - IncFIIK.Interpretation & conclusions:This study provides insight into the predominance of various β-lactamases and potent gene-disseminating agents in Klebsiella spp. and emphasizes the need for constant surveillance of these pathogens to determine appropriate treatment strategies.