Phenolic compounds, including avenanthramides, and antioxidant properties in conventionally and organically grown oat cultivars affected by germination

Oats ( Avena sativa L.) are increasingly recognized for their health benefits, particularly due to their unique avenanthramides (AVNs) and diverse phenolic acid content. While germination is known to influence polyphenol contents, the effects on AVNs and phenolic acids in Austrian oat cultivars have not been previously characterized. This study investigated in detail the AVNs, individual phenolic acids, antioxidant and enzymatic activity in four Austrian oat cultivars (Erlebek, Max, Enjoy, Earl) grown under conventional and organic conditions and germinated for 0-192 hours. Samples were analyzed for total phenolic content (TPC), antioxidant potential, AVNs, enzymatic activity, and soluble sugars using advanced assays and chromatography techniques for detailed profiling. Results showed that germination significantly increased AVN levels, phenolic acids, antioxidant activity, and α-amylase activity, with optimal germination time detected at 72-96 hours. AVN concentration in the Erlbek cultivar cultivated organically increased around 3.6-fold after 96 hours of germination. Total bound phenolics, mainly ferulic and p-coumaric acids levels increased significantly, with conventionally grown Erlbek showing a 2.8-fold increase after 96 hours (1290 ± 70 μg/g ferulic acid (FA) and 3640 ± 60 μg/g d.b., respectively)Organically grown oats generally exhibited higher concentrations of phenolics, AVNS, antioxidant potential and enzymatic activity. Among cultivars, Earl demonstrated the highest TPC and enzymatic activity, while Erlbek had the highest AVN and phenolic acid levels, especially after 72 hours germination (150 ± 10 μg/g FA and 3640 ± 60 μg/g d.b., respectively). Total AVNs in organic Erlbek were 2-times higher at 0 hours (97 ± 7 and 50 ± 7 μg/g d.b) and were the highest at 72 hours (194 ± 10 μg/g d.b), with AVN B being the most abundant. Cultivation method and cultivar had little effect on the increase in antioxidant potential over germination time. Antioxidative potential increased consistently with germination time, independently of cultivation method and cultivar • Germination increased avenanthramides, phenolic acids, and α-amylase activity. • Organic cultivation led to higher α-amylase activity and phenolic compound levels. • Avenanthramides, unique to oats, showed strong cultivar and environment dependence. • Optimal germination time for all cultivars was 72-96 hours. • Earl oats (organic, 72-96 hours) had the best phenolic and antioxidant profile.