Free and bound minor polar compounds in oats: Different extraction methods and analytical determinations

The extraction capacity of several solvent mixtures and comparison between alkaline and acid hydrolysis to extract free and bound minor polar compounds in oat samples were carried out. The extraction yield of each method was evaluated by correlating several spectrophotometric indices (absorption at 320 nm and total phenolic compounds by the Folin–Ciocalteu method) with HPLC-MS and the antioxidant activities of the oat extracts (DPPH radical method). The results showed that methanol and alkaline hydrolysis reported the highest recovery of polar compounds, and spectrophotometric indices overestimated the content of these compounds. Antioxidant compounds of five Romanian oat samples, named Comun, Jeremy, Mures, Lovrin 1, Lovrin 27-T were determined. Large intervarietal differences in phenolic compounds and their antioxidant activities among oat varieties were detected. Total minor polar contents content was in the range of 1179.47 and 1897.18 mg/kg of seed. According to the literature, we found that the majority of the minor polar compounds existed in bound form.

► Different extraction methods were carried out to obtain the highest recovery of free and bound minor polar compounds in oat. ► Different analytical methods were used to determine these compounds. ► Spectrophotometrical determinations are not suitable for the quantification of polar compounds in oat. ► Minor polar compounds in Romanian oat varieties were studied for the first time. ► Significant variations among varieties in free and bound polar compounds were demonstrated.