Phenylpropanoid glycosides from the fruit of Lycium barbarum L. and their bioactivity

Fifteen phenylpropanoid glycosides, including six undescribed compounds were isolated from the fruit of Lycium barbarum L. (Solanaceae) (goji or wolfberry). Their structures were identified by detailed spectroscopic analyses. Seven known compounds were firstly isolated from the genus Lycium, in which the 1D and 2D NMR data of one compound were reported for the first time. Notably, two undescribed compounds were a pair of rare tautomeric glycoside anomers characterized by the presence of free anomeric hydroxy. Antioxidant and hypoglycemic activities of all these compounds were assessed using DPPH radical scavenging, oxygen radical absorbance capacity (ORAC), and α-glucosidase inhibitory assays, respectively. These compounds showed different levels of oxygen radical absorbance capacity, and some isolates exhibited potent antioxidant activity with greater ORAC values than the positive control (EGCG).