Simultaneous Determination of Five Phenolic Acids and Isoquercitrin in Sweet Potato (Ipomoea batatas (L.) Lam) Leaves by HPLC

In this study, a reversed-phase high performance liquid-chromatography coupled to ultraviolet detection (RP-HPLC/UV) method for simultaneous determination of six major bioactive constituents (caffeic acid, chlorogenic acid, 3,4-dicaffeoyl quinic acid, 3,5-dicaffeoyl quinic acid, 4,5-dicaffeoyl quinic acid and isoquercetin) in sweet potato leaves was developed and validated after optimization of various chromatographic conditions and other experimental parameters. The chromatographic separation was achieved on an Agilent ZORBAX SB-C₁₈ reserved-phase column (4.6 mm×250 mm, 5 μm) using a gradient elution program with a mobile phase consisting of 0.1% formic acid aqueous solution (solvent A) and acetonitrile (solvent B) (0~12 min, 10%~25% B; 12~18 min, 25% B), at a flow rate of 0.8 mL/min, an operating temperature of 30 ℃, and a wavelength of 326 nm. The calibration curves were linear in the range of 0.25~25.0, 0.5~50.0, 5.0~100.0, 10.0~200.0, 5.0~100.0, 0.5~50.0 μg/mL for caffeic acid, chlorogenic acid, 3,4-dicaffeoyl quinic acid, 3,5-dicaffeoyl quinic acid, 4,5-dicaffeoyl quinic acid and isoquercetin, respectively. The present method was fast (18 min), and demonstrated acceptable values for linearity (R²≥0.998), stability (RSD≤1.97%), recovery (95.14%~103.22%) and precision (RSD≤1.56%). Additionally, the new method was successfully applied to determine components in sweet potato leaves from ten different regions of Jiangxi Province, and the results indicated that the sample harvested in Fengcheng city of Yichun contained higher total phenol content than those collected in other regions.