Quantification of root chicoric acid in purple coneflower by near infrared reflectance spectroscopy

Purple coneflower [Echinacea purpurea (L.) Moench] is an increasingly popular crop because of its value in the U.S. botanical industry. At present, there is no rapid method of analyzing it for chicoric acid, the predominant phenolic acid associated with immunostimulation in humans. The objective of this study was to quantify chicoric acid in purple coneflower roots by near infrared (NIR) reflectance spectroscopy. One hundred sixty-nine plants were harvested and their root tissues analyzed for chicoric acid by high performance liquid chromatography (HPLC). Root samples were scanned between 1100 and 2498 run and reflectance data recorded. The HPLC data were regressed against infrared spectra to develop empirical prediction equations. The optimum prediction equation produced coefficients of determination for calibration and cross validation of 0.90 and 0.86, respectively. The mean chicoric acid concentration was 8.29 g kg DM-1, and the standard errors of calibration and cross validation were 0.89 and 1.06 g kg DM-1, respectively. We conclude that NIR reflectance spectroscopy can accurately quantitate chicoric acid in purple coneflower.