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Development of an electrochemical method for the measurement of antioxidant capacity of pure compounds and natural substances extracts

100%

Lanez T. , Rebiai A.

International Letters of Chemistry, Physics and Astronomy

2013

tom Vol. 1

46-54

A new method has been developed to measure total antioxidant activity of antioxidants in foods and natural substances without use of standard antioxidants and without use of calibration curves plotting. It is based on measuring the oxidation peak current of superoxide anion radical electrochemically generated by reduction of commercial molecular oxygen in dimethylformamide. The method has been validated using 7 known standard antioxidants and the results have been compared with those obtained by the DPPH and molybdate ion reduction assays. Measured antioxidant capacities were highly correlated with those obtained using DPPH (r2 = 0.549) and molybdate ion reduction assay (r2 = 0.434).

Isolation of Flavonoids, Antioxidant and Antimicrobial Activities of Costus afer Ker Gawl. Stem Extracts

75%

Ekoro I. A. , Edema M. O. , Ogwuche C. E.

World News of Natural Sciences

2024

tom 53

1-16

ABSTRACT Resistance to antimicrobial agents has become an increasingly important and pressing global problem. Hence, the need for substantial investment and research in the field of anti-infectives are now desperately needed if a public health crisis is to be averted. This study aims to determine the antioxidant and antimicrobial activity of Costus afer stem and isolate the flavonoids in the extracts. The method used for isolation was a combination of thin layer chromatography (TLC) and column chromatography (CC). Phytochemical screening tests were used for identification of the eluate fractions of CC to ascertain the flavonoid-rich fraction. The flavonoid content in dry stem extracts (DSE); 153 µg/g was lesser than that in fresh stem extracts (FSE) 186 µg/g. All the extracts showed activity against test organisms (Staphylococcus aureus, Escherichia coli, Pseudomonas spp.) in a concentration-dependent manner. There was an observed resistance of S. aureus against FSE at 25 mg/ml. E.coli and Pseudomonas spp were sensitive to DSE at almost all concentrations Pseudomonas spp was sensitive to almost all the control drugs except cefuroxime where it recorded a resistance. DPPH radical scavenging activity was positively correlated to the concentration of the stem extracts. FSE sample showed higher DPPH radical scavenging activity than DSE as evident in Table 3 and Fig. 2. The reducing power of the extracts followed the order of DSE < FSE < VITC. ABTS radical scavenging activity was also positively correlated to the concentrations of the stem extracts. In this analysis, FSE sample showed higher radical scavenging activity of ABTS than the DSE sample.