Combinatorial activity of flavonoids with antibiotics against drug resistant Staphylococcus aureus

The use of resistance-modifying agents is a potential strategy that is used to prolong the effective life of antibiotics in the face of increasing antibiotic resistance. Since certain flavonoids are potent bacterial efflux pump inhibitors, we assessed morin, rutin, quercetin, hesperidin, and (+)-catechin for their combined activity with the antibiotics ciprofloxacin, tetracycline, erythromycin, oxacillin, and ampicillin against drug-resistant strains of Staphylococcus aureus, including methicillin-resistant S. aureus. Four established methods were used to determine the combined efficacy of each combination: microdilution checkerboard assays, time-kill determinations, the Etest, and dual disc-diffusion methods. The cytotoxicity of the flavonoids was additionally evaluated in a mouse fibroblast cell line. Quercetin and its isomer morin decreased by 3- to 16-fold the minimal inhibitory concentration of ciprofloxacin, tetracycline, and erythromycin against some S. aureus strains. Rutin, hesperidin, and (+)-catechin did not promote any potentiation of antibiotics. Despite the potential cytotoxicity of these phytochemicals at a high concentration (fibroblast IC50 of 41.8 and 67.5mg/L, respectively), quercetin is commonly used as a supplement for several therapeutic purposes. All the methods, with exception of the time-kill assay, presented a high degree of congruence without any apparent strain specificity.This work was supported by Operational Program for Competitiveness Factors—COMPETE, FCT/MEC (PIDDAC), and FEDER through Projects Bioresist—PTDC/EBB-EBI/ 105085/2008; Phytodisinfectants—PTDC/DTP-SAP/1078/ 2012 (COMPETE: FCOMP-01-0124-FEDER-028765) and the PhD grants awarded to Ana Abreu (SFRH/BD/84393/ 2012) and Anabela Borges (SFRH/BD/63398/2009). The authors are very grateful to Professor Simon Gibbons (De- partment of Pharmaceutical and Biological Chemistry, The School of Pharmacy, UCL School of Pharmacy, London) for providing the bacterial strains.info:eu-repo/semantics/publishedVersio

Genotoxicity studies of the bracken fern constituents quercetin, shikimate and ptaquiloside in vitro in salmonella typhimurium and in vivo in rats and mice

SIGLEAvailable from British Library Document Supply Centre- DSC:DX174147 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Possible involvement of Dioscorea species in human poisoning at Bwakila Juu in Morogoro Rural District, Tanzania

For many years‘ wild plants are known to be used as a source of food, medicines, poisons and for ornamental purposes. Dioscorea are reported to be poisonous but if well processed the local people in places where they are found eat them as food especially during hunger. The purpose of this study was to assess the toxicity of Dioscorea spp. after it was reported that the plant was involved in deaths of two humans in Bwakila Juu in Morogoro Rural District. Two types of Dioscorea bulbils were collected, one being aerial (D1) and the second was tuber (D2), they were sliced, dried under the sun and grounded to make coarse powder. Toxicity test of Dioscorea spp. was done using 4 weeks 60 cockerels which were allocated into 6 groups each consisting of 10 birds. Cockerels in groups I – III were fed with chick starter mash which was mixed with D1 Dioscorea bulbils coarse powder at a concentration of 0%, 10% and 20%; group IV - VI were fed D2 bulbils‘ coarse powder mixed with chick starter mash at a concentration of 0%, 10% and 20%. The feeding experiment was done for four days and any changes in clinical signs and deaths were observed for 7 days. In addition, blood samples were collected from all the birds on day 7 of the experiment to measure for aspartate aminotransferase enzyme (AST), albumin and total protein. All the cockerels in group III fed on 20% of D1 started developing clinical signs of inappetence, ruffled feathers, severe diarrhea, convulsion and torticollis. On day 1 of feeding, one bird died and the other two deaths were recorded on day 2. Postmortem results indicated generalized hemorrhages in the lungs and atria, hyperemia of the atria, congestion of kidneys, mucohaemorrhagic intestinal contents and generalized enteritis. The birds in the other groups appeared normal throughout the 7 days of observation but were all sacrificed for postmortem examination which again did not show significant lesions. The mean AST concentration in the plasma (16.9 ± 0.2 μg/l) of the treated birds was significantly higher (p<0.05) compared to the birds in the control groups which is an indication of the liver damage. The total protein and albumin in plasma of all the birds was within normal ranges. Almost six incidences of Dioscorea spp. poisoning in humans in which lead to death were reported by the local people in Bwakila Juu during different periods normally occurred during shortage of food. These preliminary results suggest that Dioscorea spp. may be involved in human poisoning. More studies are recommended before concluding with certainty the involvement of Dioscorea spp. in human poisoning.Keywords: wild plants, Dioscorea, poisoning, cockerel