Phenolic Composition and Antioxidant Activity in Hulless Barley Grass: Effect of Harvesting Frequency and Planting Environments

ABSTRACT Background and Objectives Hulless barley grass is rich in phenolic compounds. Yield‐optimized cultivation methods, including frequent harvesting and plant factory production, may affect these bioactive compounds, requiring systematic evaluation. Materials/Methods Two hulless barley varieties, Nanlonggela and Qinghaihuang, were cultivated in a natural field and a controlled‐environment plant factory. The field‐grown hulless barley grass was harvested three times. Phenolic content, antioxidant activity, and composition were determined across all samples. Results and Conclusion Total phenolic content of second harvest extracts (N‐2, Q‐2) was 1.45 and 1.71 times higher, respectively, while total flavonoid content was 1.39 and 1.92 times higher than the first harvest (N‐1, Q‐1). The second and third harvests showed higher antioxidant activity than the first harvest. FRAP values for N‐2 and Q‐2 were 1.36 and 1.04 times higher than N‐1 and Q‐1, respectively. Plant factory‐grown Nanlonggela and Qinghaihuang extracts exhibited FRAP values of 201 ± 9.6 μmol TE/mg GAE and 141 ± 9.5 μmol TE/mg GAE, respectively, which were lower than those from the field. HPLC and UPLC‐Q‐TOF/MS identified the main phenolic compounds in Nanlonggela as 3‐O‐[β‐ D ‐glucopyranosyl‐(1 → 2)]‐β‐ D ‐glucopyranosyl‐kaempferol and 7‐O‐α‐L‐rhamnosyl‐3‐O‐β‐D‐glucopyranosyl‐kaempferol, and in Qinghaihuang as (‐)‐suspensaside B, schinicoumarin, and apigenin‐6‐C‐glucosylglucoside. Significance This study supported cultivation of high‐quality hulless barley grass to facilitate functional product development.