Hamamelitannin’s Antioxidant Effect and Its Inhibition Capability on α-Glycosidase, Carbonic Anhydrase, Acetylcholinesterase, and Butyrylcholinesterase Enzymes

Hamamelitannin (2′,5-di-O-galloyl-hamamelose) bears two-gallate moieties in its structure, and is a natural phenolic product in the leaves and the bark of Hamamelis virginiana. The antioxidant capacity of hamamelitannin was evaluated by a range of methods, with the following findings: the ability to reduce potassium ferric cyanide; the scavenging of N,N-dimethyl-p-phenylenediamine dihydrochloride radical (DMPD•+); the scavenging of 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulphonate) radical (ABTS•+); the scavenging of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH•); and the ability to reduce cupric ions (Cu2+). Additionally, reference antioxidants of α-Tocopherol, butylated hydroxyanisole (BHA), Trolox, and butylated hydroxytoluene (BHT) were used for comparison. For DPPH radical scavenging, hamamelitannin had an IC50 value of 19.31 μg/mL, while the IC50 values for BHA, BHT, Trolox, and α-Tocopherol were 10.10, 25.95, 7.05, and 11.31 μg/mL, respectively. The study found that hamamelitannin functioned similarly to BHA, α-tocopherol, and Trolox in terms of DPPH• scavenging, but better than BHT. Additionally, as a polyphenolic secondary metabolite, the hamamelitannin inhibition capability of several metabolic enzymes was demonstrated, including acetylcholinesterase (AChE), butyrylcholinesterase (BChE), carbonic anhydrase I (CA I), carbonic anhydrase II (CA II) and α-glycosidase. The Ki values of hamamelitannin exhibited 7.40, 1.99, 10.18, 18.26, and 25.79 nM toward AChE, BChE, hCA I, hCA II, and α-glycosidase, respectively.