Flavonol glycosides and their α-glucosidase inhibitory effect from Camellia sinensis

Nguyen Thi Cucae, Luu The Anhc, Nguyen The Cuongb, Nguyen Hoang Anhf, Nguyen Xuan Nhiemae, Bui Huu Taiae, Nguyen Thi Hoaid, Pham Hai Yena, Chau Van Minha,Phan Van Kiemae

aInstitute of Marine Biochemistry, Vietnam Academy of Science and Technology (VAST), 18 Hoang Quoc Viet, Cau Giay, Hanoi, Viet Nam

bInstitute of Ecology and Biological Resources, VAST, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Viet Nam

cCentral Institute for Natural Resources and Environmental Studies, Vietnam National University, Hanoi, 19 Le Thanh Tong, Hoan Kiem, Hanoi, Viet Nam

dFaculty of Pharmacy, Hue University of Medicine and Pharmacy, Hue University, 6 Ngo Quyen, Hue, Viet Nam

eGraduate University of Sciences and Technology, VAST, 18 Hoang Quoc Viet, Cau giay, Hanoi, Viet Nam

fFaculty of Chemistry, Thai Nguyen University of Science, Tan Thinh, Thai Nguyen, Viet Nam

Received 9 June 2019, Revised 24 October 2019, Accepted 13 November 2019, Available online 21 November 2019.

Phytochemistry Letters Volume 35, February 2020, Pages 68-72: https://doi.org/10.1016/j.phytol.2019.11.013

Highlights

• Three new compounds were isolated from Camellia sinensis.
• The structures were successfully determined by spectroscopic evidence.
• Comp. 4 exhibited the strongest α-glucosidase inhibitory activity (57.2 %.).
• Comp. 1, 2, and 4–8 showed α-glucosidase inhibitory activity with inhibitory percentages of 20.4–41.1 %.

AbstractTwo new flavonol glycosides, kaempferol 3-Oαl-rhamnopyranosyl-(1→6)-[αl-arabinopyranosyl-(1→3)] [2-(Z)-coumaroyl]-βd-glucopyranoside (1) and 4′-Oαl-rhamnopyranosylkaempferol 3-Oαl-rhamnopyranosyl-(1→6)-[αl-arabinopyranosyl-(1→3)] [2-(Z)-coumaroyl]-βd-glucopyranoside (2), one new megastigmane glycoside, (3S,9R)-3,9-dihydroxymegastigman-5-ene 9-Oβ-d-apiofuranosyl-(1→6)-β-d-glucopyranoside (3), along with five known compounds, 7S,8Sthreo 4,9,9′-trihydroxy-3,3′-dimethoxy-8-O-4′-neolignan 7-Oβd-glucopyranoside (4), kaempferol 3-Oβd-glucopyranoside (5), nicotiflorin (6), 4′-Oαl-rhamnopyranosylnicotiflorin (7), and camelliquercetiside (8) were isolated from the methanol extract of the leaves of Camellia sinensis (L.) Kuntze. Their structures were elucidated by 1D, 2D NMR spectra, HR-ESI-MS, chemical methods, and by comparing with the NMR data reported in the literature. In addition, the α-glucosidase inhibitory activity of all compounds was evaluated. As the results, compound 4 exhibited the strongest α-glucosidase inhibitory activity (57.2 %), while flavonol glycosides 12, and 58 showed α-glucosidase inhibitory activity with inhibitory percentage ranging from 20.4 to 41.1 %.

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