Phytochemical diversity and antioxidant capacity of citrus cultivars in Zhejiang: a phenolic profiling study for resource evaluation and differentiation

To elucidate the under-characterized phytochemical diversity of regionally important citrus germplasm, this study performed a comparative analysis of phenolic profiles and antioxidant activities in seven cultivars from Zhejiang Province, including commercial, locally adapted and emerging varieties. Using UPLC-MS/MS, 17 flavonoids and 11 phenolic acids were quantified in peel and pulp tissues, revealing significant metabolite differentiation among varieties. The hybrid variety Gaocheng (pomelo × orange) displayed a distinct intermediate chemotype. It was characterized by the concurrent accumulation of naringin, and hesperidin. Notably, the peels of Ponkan, Bendizao, Gaocheng, and Miyagawa wase were identified as rich sources of bioactive PMFs. All peel extracts exhibited strong antioxidant activity, with Gaocheng showing the highest comprehensive antioxidant capacity. PCA and HCA revealed that phenolic composition was strongly associated with genetic background, classifying the varieties into three distinct groups. Collectively, these findings provide a foundation for the utilization of citrus by-products, cultivar authentication, and breeding strategies for enhanced bioactivity.