A new ultra-high pressure liquid chromatography method for the determination of antioxidant flavonol aglycones in six <i>Lysimachia</i> species

<p>UPLC-DAD method was developed and validated for the quantitative determination of free flavonol aglycones (kaempferol, quercetin and myricetin) after acidic hydrolysis in six <i>Lysimachia</i> species. Quantitative analyses showed that the amounts of various flavonol aglycones were significantly different in <i>Lysimachia vulgaris</i>, <i>Lysimachia nummularia</i>, <i>Lysimachia punctata</i>, <i>Lysimachia christinae</i>, <i>Lysimachia ciliata</i> and <i>Lysimachia clethroides</i>. The <i>L. clethroides</i> sample was found to be the richest in kaempferol (25.77 ± 1.29 μg/mg extract) and quercetin (97.67 ± 4.61 μg/mg extract), while the <i>L. nummularia</i> sample contained the highest amount of myricetin (20.79 ± 1.00 μg/mg extract). The antioxidant capacity of hydrolysed extracts was evaluated using <i>in vitro</i> DPPH<sup>•</sup> (2,2-diphenyl-1-picrylhydrazyl) and ABTS<sup>•+</sup> [2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid)] decolourisation tests. The observed radical scavenging capacities of the extracts showed a relationship with the measured flavonol aglycone content and composition. The acidic treatment resulted in an increased free radical scavenging activity compared to the untreated methanol extract.</p>