Quality control of corn silk extract using IR spectroscopy along with statistical methods

Aqueous extracts of corn silk exhibit glycation-inhibitory activity. Lignin is the active component of these extracts. As corn silk is highly nutritious and has medicinal value, it can be used as a functional food and cosmetics. However, to achieve this goal, it is necessary to evaluate its quality. As lignin, which could be used as a marker compound for quality control, is a macromolecule, HPLC cannot be employed for the quality control of the aqueous extracts of corn silk. We here develop a method to evaluate the anti-glycation activity of the aqueous extracts of corn silk using attenuated total reflectance (ATR)-Fourier transform infrared (FTIR) spectroscopy along with multivariate statistical analysis. The inhibitory activity was evaluated using two multivariate calibrations: principal component regression (PCR) and partial least square regression (PLSR). The spectral areas of the PCR model were 633.5-880.3, 1191.8-1359.6, 1423.1-1492.6, and 2572.6-2974.7 cm^-1. Its coefficient of correlation (R² = 0.981) and root mean square error of cross validation (RMSECV = 2.356) were highly predictable. The spectral regions of 983.5-985.5 and 1021.1-1107.9 cm^-1 offered the best prediction models for the PLSR model. The R² value for the correlation between the actual values and the FTIR-predicted values was 0.994, while the corresponding RMSECV was 1.325%. Hence, FTIR spectroscopy along with multivariate calibration is a useful method for evaluating active corn silk aqueous extracts.