Quantification of Total Phenolic Content and Antioxidant Activity of Oat Cultivars Grown in South Dakota

Oats grown in different locations of South Dakota were analyzed for the crop years of 2011 and 2012. The sampling locations consisted of Brookings, Miller, SE Farm, Selby and Warner. The objectives of this study were to evaluate the correlation of total phenolic content (TPC) and antioxidant activity (AA %) of oat samples. High performance liquid chromatography (HPLC) was used to analyze the oat samples for avenanthramide content. The total phenolic content was measured using AOAC method (method # 952.03, 1990). Extraction protocols were optimized for oat samples. Antioxidant activity, the free radical scavenging effect of oat extracts, was measured using the 1, 1 diphenyl 2 picrylhydrazyl (DPPH) assay. Pure standards (tannic acid, quercetin, 5- hydroxyanthranillic acid, caffeic acid, ferulic acid, p-coumaric acid, and sinapic acid) were tested to allow for data interpretation and method validation. Total phenolic content ranged from 78.6 mg Tannic Acid Equivalents (TAE)/100g to 149.1 mg TAE/100g and antioxidant activity ranged from 13% to 22% for the 2011 and 2012 crops. Quercetin used as an antioxidant activity reference yielded 88.5% antioxidant activity. Correlation found between total phenolic content and antioxidant activity for the 2011 year samples (n= 89) was 38%. Weak correlation was found between total phenolic content and antioxidant activity for the 2012-year samples (n= 70). Phenolic compounds were responsible for some of the antioxidant activity in the 2011 crop. Avenanthramide content was determined to be unique in oat extract, which was measured by HPLC. The avenanthramide content present in the oat samples explained 60% variance of total phenolic content (n=50). Weak correlation was observed between avenanthramide content and antioxidant activity in the same samples. Correlation of TPC and AA% for growing locations showed a maximum of 59% correlation for the Selby location for the 2011 crop. For the 2012 crop, Miller location showed 27.3% correlation between TPC and AA%. Two crop years 2011 and 2012 showed variation in TPC and AA% between growing locations and cultivars