Modeling of Antioxidant Activity, Polyphenols and Macronutrients Content of Bee Pollen Applying Solid-State ¹³C NMR...

An application of solid ¹³C nuclear magnetic resonance (NMR) spectroscopy for the determination of macronutrients, total polyphenols content, antioxidant activity, N C S elements, and pH in commercially available bee pollens is reported herein. Solid-state ¹³C NMR spectra were recorded for homogenized pollen granules without chemical treatment or dissolution of samples. By combining spectral data with the results of reference analyses, partial least squares models were constructed and validated separately for each of the studied parameters. To characterize and compare the models' quality, the relative standard errors of prediction (RSEP) were calculated for calibration and validation sets. In the case of the analysis of protein, fat and reducing sugars, these errors were in the 1.8-2.5% range. Modeling the elemental composition of bee pollen on the basis of ¹³C NMR spectra resulted in RSEP_cal/RSEP_val values of 0.3/0.6% for the sum of NHCS elements, 0.3/0.4% for C, 1.8/1.9% for N, and 4.2/6.1% for S quantification. Analyses of total phenolics and ABTS antioxidant activity resulted in RSEP values in the 2.7-3.5% and 2.8-3.8% ranges, respectively, whereas they were 1.4-2.1% for pH. The obtained results demonstrate the usefulness of ¹³C solid-state NMR spectroscopy for direct determination of various important physiochemical parameters of bee pollen.