Phenolic Content, Antioxidant Capacity, and α-amylase and α-glucosidase Inhibitory Activities of Dimocarpus longan Lour

The aim of this study was to compare the phenolic compound profiles and antioxidant capacities of eight varieties of longan (Dimocarpus longan Lour.) planted in the middle and upper Yangtze River area. The total polyphenols content (TPC) and total flavonoids content (TFC) of dried longan pulp ranged from 1.07 ± 0.05 to 1.22 ± 0.05 mg gallic acid equivalents/g and 0.25 ± 0.07 to 0.87 ± 0.14 mg rutin equivalents/g. UHPLC-QqQ-MS/MS analysis revealed 12 individual polyphenol compounds in longan. The Fuwan8, Dongliang and FD97 varieties showed the strongest DPPH scavenging activity (IC₅₀ of 1.03 g/mL). The highest ABTS⁺ scavenging activity was found in the Dongliang. In the enzyme assays, the Fuwan8 and Dongliang varieties demonstrated maximum α-amylase and α-glucosidase inhibition activities, with values of 97.56 and 88.58%, respectively. The principal component analysis indicated that the Rongyu8 and Songfengben cultivars have nearly analogous polyphenol compounds.

Keywords: Antioxidant; Longan; Polyphenol; α-Amylase; α-Glucosidase.