chrysin and thiazolyl-blue

Antioxidants scavenge free radicals, singlet oxygen, and electrons in cellular redox reactions. The yellow MTT [3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide] is reduced to a purple formazan by mitochondrial enzymes. NADPH is the basis of established in vitro cell viability assays. An antioxidant assay has been developed utilizing the redox reaction between MTT and selected natural product extracts and purified compounds. This simple, fast, and inexpensive MTT antioxidant assay is comparable with the lipid peroxidation inhibitory assay and can be mechanized to achieve high throughput.

Topics: Antioxidants; Coloring Agents; Formazans; Free Radical Scavengers; Mitochondria; Molecular Structure; NADP; Oxidation-Reduction; Plant Extracts; Singlet Oxygen; Tetrazolium Salts; Thiazoles

We evaluated the antifilarial activity of 6 flavonoids against the human lymphatic filarial parasite Brugia malayi using an in vitro motility assay with adult worms and microfilariae, a biochemical test for viability (3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT)-reduction assay), and two animal models, Meriones unguiculatus (implanted adult worms) and Mastomys coucha (natural infections). In vitro, naringenin and hesperetin killed the adult worms and inhibited (>60%) MTT-reduction at 7.8 and 31.2 μg/ml concentration, respectively. Microfilariae (mf) were killed at 250-500 μg/ml. The half maximal inhibitory concentration (IC(50)) of naringenin for motility of adult females was 2.5 μg/ml. Flavone immobilized female adult worms at 31.2 μg/ml (MTT>80%) and microfilariae at 62.5 μg/ml. Rutin killed microfilariae at 125 μg/ml and inhibited MTT-reduction in female worms for >65% at 500 μg/ml. Naringin had adulticidal effects at 125 μg/ml while chrysin killed microfilariae at 250 μg/ml. In vivo, 50 mg/kg of naringenin elimiated 73% of transplanted adult worms in the Meriones model, but had no effect on the microfilariae in their peritoneal cavity. In Mastomys, the same drug was less effective, killing only 31% of the naturally acquired adult worms, but 51%, when the dose was doubled. Still, effects on the microfilariae in the blood were hardly detectable, even at the highest dose. In summary, all 6 flavonoids showed antifilarial activity in vitro, which can be classed, in a decreasing order: naringenin>flavone=hesperetin>rutin>naringin>chrysin. In jirds, naringenin and flavone killed or sterilized adult worms at 50mg/kg dose, but in Mastomys, where the parasite produces a patent infection, only naringenin was filaricidal. Thus naringenin and flavone may provide a lead for design and development of new antifilarial agent(s). This is the first report on antifilarial efficacy of flavonoids.

Topics: Animals; Brugia malayi; Coloring Agents; Disease Models, Animal; Elephantiasis, Filarial; Female; Filaricides; Flavanones; Flavonoids; Gerbillinae; Hesperidin; Humans; Male; Murinae; Rutin; Survival Analysis; Tetrazolium Salts; Thiazoles