Analysis of rare flavonoid C-glycosides in Celtis australis L. by micellar electrokinetic chromatography

This manuscript reports on the first analytical procedure for the determination of flavonoids in Celtis australis. The capillary electrophoretic separation of 8 compounds, most of them flavone C-glycosides, was possible using a borax buffer with pH 9.0, which contained 25 mM SDS as detergent and 7.5% of n-butanol as organic modifier. Method validation revealed that the developed assay is repeatable (σrel ≤ 4.0%), precise (inter-day σrel ≤ 6.7%, intra-day σrel ≤ 3.9%), accurate (recovery rates from 96.8 to 102.3%), sensitive (LOD: 2.2–1.6 μg/ml) and linear (R2 ≥ 0.9996) within the tested concentration range. The quantitative analysis of several C. australis samples showed that isovitexin is the most abundant representative (0.06–0.09%), at a rather uniform content of total flavonoids of approx. 0.3% in all specimens.