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PubMed2004

Accurate determination of oosporein in fungal culture broth by differential pulse polarography.

A simple and accurate differential pulse polarographic method has been developed for the determination of oosporein in the culture broth of the fungus Beauveria brongniartii. This hydroxybenzoquinone derivative is the only major secondary metabolite secreted by this entomopathogenic fungus, which is used as biological pest control agent (BCA) against Melolontha melolontha larvae. It can be found in the host organism as well as in the formulated product. The polarographic behavior of oosporein was examined in various buffer systems over the pH range 3-10. In Britton-Robinson buffer/methanol solution (3:7 v/v, pH 5.5) the differential pulse polarograms exhibited reproducible peaks at E(p) = -0.18 V vs silver/silver chloride/potassium chloride (3 M). Under these conditions, a plot of peak height vs concentration of oosporein was found to be linear over the range 5.9 x 10(-)(7) to 2.5 x 10(-)(5) M (0.18-7.74 microg mL(-)(1); r = 0.9998). The detection limit was calculated to be 54 ng mL(-)(1). To evaluate the concentration of oosporein, the standard addition method was applied. The analysis of oosporein in the culture broth led to a mean value of 524.9 microg mL(-)(1) broth with a relative standard deviation (S(rel)) of +/-2.6%. The proposed polarographic method is accurate, not time-consuming, and it is of low cost because no separation steps are necessary.

Ascomycota↗
PubMed1990

Applications of oxygen polarography to drug stability testing and formulation development: solution-phase oxidation of hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors.

The kinetics of oxidation of the HMG-CoA reductase inhibitors lovastatin, simvastatin, L-157,012, and L-647,318 were studied in an aqueous surfactant solution. A thermally labile free radical initiator was used to attain measurable reaction rates at 40 degrees C and rate constants were determined by measuring oxygen consumption using an oxygen electrode. The stability of the drugs was found to increase in the order lovastatin = simvastatin less than L-157,012 less than L-647,318. The addition of butylated hydroxyanisole (BHA) was found to stabilize the drugs. For the oxidation of lovastatin, the effectiveness of antioxidants increased in the order propyl gallate less than BHA less than alpha-tocopherol. It is concluded that the stability of oxidizable drugs can be rapidly and conveniently assessed by the techniques described herein.

Antioxidants↗