Comparison of antioxidant activity of dihydroquercetin samples with different diastereomeric composition

Introduction. Flavanonol dihydroquercetin (DHQ) is known for its pronounced antioxidant properties, which are associated with a wide range of biological activity of this compound. Due to the presence of two chiral centers at positions 2 and 3 of the benzopyranone ring, this flavonoid is characterized by the phenomenon of cis-trans isomerism. However, a comparative analysis of the antioxidant properties of DHQ diastereomers has not been performed before. Aim. To evaluate the effect of diastereomeric composition on the reducing and radical scavenging properties of DHQ samples. Materials and methods. The diastereomeric composition of the DHQ samples was controlled under reverse phase chromatography with UV detection. The antioxidant capacity was studied using a model of inhibition of radical cations of 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS +• ). The reducing ability of the DHQ samples was evaluated using a 5-(2,4-disulfophenyl)-3-(2-methoxy-4-nitrophenyl)-2-(4-nitrophenyl)-2 H -tetrazolium monosodium salt (WST-8) model. Both tests were performed under the control of UV spectrophotometry. Results and discussion. The chromatograms of the samples obtained at 288 nm are characterized by two peaks with retention times of 18.79 ± 0.08 and 19.87 ± 0.08 min, which correspond to trans - and cis -diastereomers of DHQ. After 6 minutes of DHQ samples containing 0.8, 3.7, and 9.5 % of the cis-isomer adding to the ABTS •+ solution, the optical density at 730 nm decreased by 0.588 ± 0.008, 0.581 ± 0.017, and 0.602 ± 0.012, respectively (α 0.05, p 0.2196, r 0.7857), while in WST-8 solutions at 450 nm for similar samples, an increase in optical density was observed by 0.178 ± 0.030, 0.222 ± 0.026, and 0.188 ± 0.036, respectively (α 0.05, p 0.5157, r 0.0284). Conclusion. These results indicate that there is no significant effect of the diastereomeric composition on the antioxidant properties of the DHQ samples. Thus, the observed differences in the pharmacology of cis - and trans -DHQ should be explained by the selectivity of interaction with biological targets, rather than the free radicals scavenging activity.