The antioxidant activity (AA), total phenolic content (TPC) and total flavonoids content (TFC) in Dong quai (DQ, Angelica sinensis) raw materials and dietary supplements (DS) containing this plant were determined using the CUPRAC, FRAP and fluorescence methods. The antioxidant activity for DQ aqueous extracts revealed by CUPRAC was (1330.45 ± 1.30) µmol Trolox equivalent (TE) per 100 g of dry mass (DM), whereas the antioxidant activity as determined by FRAP was (1813.9 ± 2.0) µmol of TE per 100 g of DM. Lower values were noted for the fluorescence method than for CUPRAC and FRAP (ranging from (35.96 ± 0.3) to (304.6 ± 1.4) µmol of TE per 100 g of DM). The highest TPC values were determined for an aqueous extract of DQ ((3330.3 ± 2.3) µmol of TE per 100 g of DM), while TFC for ethanolic extracts of DQ was ((146.50 ± 0.5) mg of quercetin equivalent (QE) per 100 g of DM). Cinnamic acid, isomers of benzoic acid and derivatives of quercetin were analysed by HPLC-PDA. The ferulic acid concentration in an ethanolic extract of DQ was (21.83 ± 0.07) mg per 100 g of DM. Of the flavonols detected, rutin exhibited the highest concentration in ethanolic extract of DQ ((3.32 ± 0.13) mg of QE per 100 g of DM). Other phytochemicals (alkaloids, saponins, flavonoids, anthraquinones, tannins, steroids, etc.) were identified by phytoscreening colour reaction. The results were analysed by principal component analysis (PCA), cluster analysis and one-way ANOVA tests.