Antihyperglycemic, antioxidant activities of two Acer palmatum cultivars, and identification of phenolics profile by UPLC-QTOF-MS/MS: New natural sources of functional constituents

This research aimed to compare the antihyperglycemic and antioxidant abilities, and to characterize the bioactive constituents of two Acer palmatum cultivars, Acer palmatum ‘ Atropurpureum ’ (APA) and Acer palmatum Thunb (APT). Dry materials were respectively extracted with 70% and 90% methanol, followed by sequentially fractionation with ethyl acetate and n -butanol. The phytochemical profile of selected fraction was determined by using UPLC-QTOF-MS/MS. APT is a better source of natural antioxidants and α- glucosidase inhibitors than APA due to its higher total phenolic content (TPC), and stronger antioxidant and α- glucosidase inhibitory activities. The highest total phenolic and total flavonoid content were found in the ethyl acetate fraction (EAF) of 90% methanol extract of APT (468.49   mg GAE/g Extract) and 70% methanol extract of APA (142.60   mg QuE/g Extract), respectively. The EAF of 70% methanol extract of APT gave the strongest DPPH· scavenging ability, ABTS + · scavenging ability and α- glucosidase inhibitory, with the IC 50 values of 7.06, 4.18 and 1.99   μg/mL, respectively. The latter two were much higher than that of individual positive control. HPLC analysis revealed similar phytochemical profiles of all EAFs. Twenty-five compounds, including 3 organic acids, 5 phenolic acids, 8 tannins, 7 flavonoids and 2 proanthocyanidins, were identified or tentatively identified from APT, with tannins and flavonoid glucosides as the major active compounds. The results indicated a strong potential of Acer palmatum as a natural source of excellent antioxidants and antihyperglycemic compounds in the prevention and treatment of type II diabetes and its complication.