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Identification of bioactive compounds that contribute to the α-glucosidase inhibitory activity of rosemary

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Abstract

To investigate the bioactive compounds that contribute to the α-glucosidase inhibitory activity of rosemary, phenolics and triterpene acids were characterized and quantified using quadrupole-Orbitrap mass spectrometry and enzyme assay. Two phenolic diterpenes (carnosol and hydroxy p-quinone carnosic acid) and two triterpene acids (betulinic acid and ursolic acid) were identified as potent α-glucosidase inhibitors. Carnosol, a major diterpene in rosemary, showed significant α-glucosidase inhibitory activity with IC50 value of 12 μg mL−1, and its inhibition mode was competitive. The inhibition mechanism of carnosol on α-glucosidase was further investigated by a combination of surface plasmon resonance (SPR) spectroscopy, fluorescence quenching studies and molecular-modeling techniques. The SPR assay suggested that carnosol had a high affinity to α-glucosidase with equilibrium dissociation constant (KD) value of 72.6 M. Fluorescence quenching studies indicated that the binding between carnosol and α-glucosidase was spontaneous and mainly driven by hydrophobic forces. Molecular docking studies revealed that carnosol bound to the active site of α-glucosidase. Furthermore, the oral administration of carnosol at 30 mg kg−1 significantly reduced the postprandial blood glucose levels of normal mice. This is the first report on the α-glucosidase inhibition and hypoglycemic activity of phenolic diterpenes, and these results could facilitate the utilization of rosemary as a dietary supplement for the treatment of diabetes.

Graphical abstract: Identification of bioactive compounds that contribute to the α-glucosidase inhibitory activity of rosemary

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Supplementary files

Article information


Submitted
18 Oct 2019
Accepted
04 Feb 2020
First published
06 Feb 2020

Food Funct., 2020, Advance Article
Article type
Paper

Identification of bioactive compounds that contribute to the α-glucosidase inhibitory activity of rosemary

Y. Ma, D. Zhao, R. Zhang, X. He, B. Q. Li, X. Zhang, Z. Wang and K. Zhang, Food Funct., 2020, Advance Article , DOI: 10.1039/C9FO02448D

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