Principal phenolic phytochemicals and antioxidant activities of three Chinese medicinal plants

The principal antioxidant components and content of cinnamon (Cinnamomum cassia), turmeric (Curcuma longa) and golden thread (Coptidis rhizoma) extracts were determined using high performance liquid chromatography (HPLC) with UV detection. In general, C. cassia, C. longa and C. rhizoma extracts from domestic Taiwan were rich in cinnamaldehyde, curcumin, and berberin, respectively. The contents of cinnamaldehyde, curcumin, and berberin in the acetone extracts were 1911, 2029, and 840 mg l⁻¹, respectively. The Folin–Ciocalteu method was used to measure the total phenolic concentrations of extracts, which had the content of 9.6 (C. cassia), 2.6 (C. longa), and 4.3 (C. rhizoma) mM l⁻¹. In addition, DPPH radical-scavenging, ferric-reducing antioxidant power (FRAP), and ferric thiocyanate (FTC) assays were employed to measure antioxidant activities. The C. cassia fresh extracts had higher antioxidant activities which were 84–90% (DPPH), 17–33 μmol l⁻¹ (FRAP), and 53–82% (FTC). The activities of C. longa fresh extracts were 22–44% (DPPH), 7–11 μmol l⁻¹ (FRAP), and 53–81% (FTC) while C. rhizoma were 53–64% (DPPH), 18–26 μmol l⁻¹ (FRAP), and 59–82% (FTC).