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HPLC, Two-Dimensional TLC Determination of Phenolic Content, and an In Vitro Perspective to Antioxidant Potential of Euonymus verrucosus Scop. Extracts

100%

Kukula-Koch W. , Widelski J. , Koch W. , Głowniak K.

2015

tom Vol. 27, no. 4

743--754

The presence of phenolic content in overground extracts of Euonymus verrucosus Scop. — commonly growing in Europe — has been reported recently. The chromatographical and spectral data revealed the presence of several simple phenolic acids (gallic, protocatechuic, p-hydroxybenzoic, vanillic, syringic, caffeic, p-coumaric, ferulic, and m-coumaric acids), both as free and conjugated with other secondary metabolites. The comparison of two-dimensional TLC systems on cellulose stationary phases with HPLC— DAD reversed-phase chromatography was performed to assess a cheap and rapid technique in the identification process of major phenolic constituents. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging tests, expressed as IC50, revealed the most beneficial results for the fraction after alkaline hydrolysis and yielded 205 ± 8 μg mL−1.

Influence of 2,5-dichloro-1,4-benzoquinone on jack bean urease activity. Inhibitory effect, total reducing capacity and DPPH radical scavenging activity

84%

Kot M. , Olech Z.

nr 4

Inhibition of jack bean activity by 2,5-dichloro-1,4-benzoquinone (DCBQ) was studied in phosphate buffer, pH 7.0. It was found that DCBQ acted as a strong, time and concentration dependent inactivator of urease. Under the experimental conditions obeyed the terms of pseudo-first-order reaction, urease was totally inactivated. Application of Wilson-Kitz method proved that the urease-DCBQ interaction followed a simple bimolecular process and the presence of intermediate complex was undetectable. The determined second order rate constant of the inactivation was 0.053 (μM min)-1. Thiols such as l-cysteine, glutathione and dithiothreitol (DTT) protected urease from inhibition by DCBQ but DCBQ-modified urease did not regain its activity after DTT application. The thiol protective studies indicated an essential role of urease thiol(s) in the inhibition. The irreversibility of the inactivation showed that the process was a result of a direct modification of urease thiol(s) by DCBQ (DCBQ chlorine(s) substitution). The decomposition of DCBQ in aqueous solution at natural light exposure was monitored by visible spectrophotometry, determination of the total reducing capacity (Folin-Ciocalteu method) and DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging ability. The DCBQ conversion resulted in a decrease of the inhibition power and was well correlated with the increase of the total reducing capacity and DPPH scavenging ability. These findings were attributed to DCBQ transformation by photolysis and the hydrolysis effect was found to be negligible.