Abstract: This study developed a high-performance liquid chromatography (HPLC) method for the simultaneous determination of 19 polyphenols in sunflower capitulum. The polyphenolic profiles and in vitro antioxidant activities of sunflower capitulum from two major production regions of Xinjiang were systematically evaluated. The optimal extraction conditions were determined as follows: 60% (V/V) methanol in water as extraction solvent, a solid-to-liquid ratio of 1:15 (g/mL), and 20-minute ultrasonic-assisted extraction. An TC-C18 (2) reversed-phase column was used for chromatographic separation. Gradient elution was performed with a mobile phase consisting of 0.1% (V/V) formic acid in water and 90% acetonitrile and the detection wavelengths were set at 280 and 330 nm with a diode array detector. Results showed that the 19 polyphenols exhibited a good linearity (R2 > 0.997 1) in the concentration range of 0.2–50 mg/L, and the spiked recovery rates were 90.1%–109.5%, with relative standard deviations (RSDs) of 0.3%–7.3%, indicating the method to be accurate and reliable. Chlorogenic acid derivatives including three monocaffeoylquinic acids (dominated by chlorogenic acid) and five dicaffeoylquinic acids (dominated by isochlorogenic acid A) were the most prevalent polyphenols in sunflower capitulum. Neochlorogenic acid, isochlorogenic acid A, isochlorogenic acid C, 1,3-dicaffeoylquinic acid and 1,5-dicaffeoylquinic acid had significant antioxidant capacity. The samples from Jimsar county exhibited significantly higher 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity and ferric reducing antioxidant power (FRAP) than did those from Altay city (P < 0.05). These findings provide an important basis for the high-value utilization of sunflower processing by-products and the development of their functional ingredients.

Key words: sunflower capitulum; polyphenols; high performance liquid chromatography; antioxidant activity