RÉSUMÉ
BACKGROUND: Cyclocarya paliurus, as a new food resource, is utilized extensively in human and animal diets due to its bioactive compounds, health benefits, and its highly prized sweet flavor. This study aimed to investigate the sweet-taste ingredient of C. paliurus leaves. RESULTS: Five new dammarane triterpenoid glycosides were isolated and identified as qingqianliutianosides A-E (1-5) by comprehensive spectroscopic data analysis and a single crystal X-ray diffraction experiment. Qingqianliutianoside A (1) and qingqianliutianoside C (3), present in relatively high quantities in the plant, were shown to exhibit sweetness by sensory evaluation and electronic tongue analysis. Further monitoring was conducted on the content changes in 3 in leaves at different growth stages, indicating that 3 reached its peak content in April and then showed a decreasing trend. Molecular docking studies revealed that T1R2/T1R3 receptors Ser212, Ser105, Thr239, Asn380, Thr305, and Val381 may play critical roles, demonstrating that hydrogen bonding and hydrophobic interactions were the dominant interaction forces between all of the identified compounds and the active sites in the Venus flytrap module of the T1R2/T1R3 receptors. CONCLUSION: Qingqianliutianosides A-E are promising natural source sugar substitutes for use in functional foods and beverages. © 2024 Society of Chemical Industry.
RÉSUMÉ
Seven previously undescribed flavonol glycosides including four rare flavonol glycoside cyclodimers, dicyclopaliosides A-C (1-3) with truxinate type and dicyclopalioside D (4) with truxillate type, as well as three kaempferol glycoside derivatives cyclopaliosides A-C (5-7), were obtained from the leaves of Cyclocarya paliurus. Their structures were elucidated by extensive spectroscopic methods and chemical analyses. All compounds were evaluated for their inhibitory α-glucosidase activities. Among them, compounds 1-4 display strong inhibitory activities with IC50 values of 82.76 ± 1.41, 62.70 ± 4.00, 443.35 ± 16.48, and 6.31 ± 0.88 nM, respectively, while compounds 5-7 showed moderate activities with IC50 values of 4.91 ± 0.75, 3.64 ± 0.68, and 5.32 ± 0.53 µΜ, respectively. The structure-activity relationship analysis assumed that the cyclobutane cores likely contribute to the enhancement of α-glucosidase inhibitory activities of dimers. Also, the interaction mechanism between flavonol glycoside dimers and α-glucosidase were explored by the enzyme kinetic assay, indicating that compounds 1-3 exhibited mixed-type inhibition, while 4 showed uncompetitive inhibition. Additionally, the active compounds have also undergone molecular docking evaluation.