Polyphenols from Acorn Leaves (Quercus liaotungensis) Protect Pancreatic Beta Cells and Their Inhibitory Activity against α-Glucosidase and Protein Tyrosine Phosphatase 1B

Abstract

Acorn leaves, which possess potential pharmacologic effects, are traditionally consumed as food in China. Phytochemical investigations of acorn leaves yielded one new and 25 known polyphenols, and their structures were identified by extensive spectroscopic analysis. Three antidiabetes assays were conducted. Compound 2 considerably increased the survival of pancreatic beta cells by reducing the production of reactive oxygen species and enhancing the activities of superoxide dismutase, catalase, and glutathione in MIN6 cells damaged by H2O2. The preliminary mechanism by which compound 2 protects pancreatic beta cells was through the nuclear factor erythroid-2-related factor 2 (Nrf2)/heme oxygenase-1 HO-1 pathway. Most of the tested isolates showed strong inhibitory activity against α-glucosidase and protein tyrosine phosphatase 1B. The IC50 values of most compounds were much lower than those of the positive control. The results suggest that polyphenols from acorn leaves are potential functional food ingredients that can be used as antidiabetic agents.

Flavonoids and Terpenoids with PTP-1B Inhibitory Properties from the Infusion of Salvia amarissima Ortega

“…In both cases, the inhibitory effect was concentration-dependent. The inhibitory activity against PTP-1B reported for compounds 4 and 6 correlated well with that found in this work [19,20]. On the other hand, rosmarinic acid (5) is an ingredient of an active extract of Rosmarinus officinalis against PTP-1B [21].…”

Medicinal Uses, Phytochemistry, and Pharmacological Activities of Quercus Species

“…e authors found that all the compounds showed strong inhibitory effects on PTP1B and α-glucosidase, but inhibition of α-amylase was not observed [87]. It was also reported that the polyphenol fraction from acorn leaves (Quercus liaotungensis) inhibited α-glucosidase and PTP1B activity [49].…”

“…Flavonoids are also found to be important bioactive compounds of Quercus leaves. Xu et al [87] conducted a study on acorn leaves (Quercus liaotungensis) and isolated one new flavonoid glycoside, namely, 2,3-diol acetonide-3-O-α-L-rhamnopyranoside-kaempferol, and 25 known polyphenolics. Recently, a study carried out on the infusion of the leaves of the six different species of Quercus revealed the presence of 7 flavan-3-ols, 2 flavonols, 18 flavonols/flavanone glycosides, 1 flavanone, 1 flavone, and 4 other unknown compounds.…”

Hypoglycemic activity of extracts of Chamaecyparis obtusa var. formosana leaf in rats with hyperglycemia induced by high-fat diets and streptozotocin

“… 28 Quercetin, kaempferol and myricetin showed the potent PTPN1 inhibitory activity as sodium orthovanadate, a phosphatase inhibitor. 29 PTPN1 inhibitory activity was increased by the degree of polymerization of proanthocyanidins. 30 CoLE contained flavonoids, flavonoid glycosides and proanthocyanidins.…”

“… 13 These compounds were reported to have PTPN1 and α-glucosidase inhibitory activities. 29 The above-mentioned studies revealed that CoLE could alleviate the symptoms of diabetes by inhibiting activity of PTPases on liver, muscle and epididymal fat. The high AUC of OGTT and FBG of hyperglycemic rats are ameliorated by CoLE treatments.…”