Magnolol and Luteolin Inhibition of α-Glucosidase Activity: Kinetics and Type of Interaction Detected by In Vitro and In Silico Studies

Abstract

Magnolol and luteolin are two natural compounds recognized in several medicinal plants widely used in traditional medicine, including type 2 diabetes mellitus. This research aimed to determine the inhibitory activity of magnolol and luteolin on α-glucosidase activity. Their biological profile was studied by multispectroscopic methods along with inhibitory kinetic analysis and computational experiments. Magnolol and luteolin decreased the enzymatic activity in a concentration-dependent manner. With 0.075 µM α-glucosidase, the IC50 values were similar for both compounds (~ 32 µM) and significantly lower than for acarbose (815 μM). Magnolol showed a mixed-type antagonism, while luteolin showed a non-competitive inhibition mechanism. Thermodynamic parameters suggested that the binding of magnolol was predominantly sustained by hydrophobic interactions, while luteolin mainly exploited van der Waals contacts and hydrogen bonds. Synchronous fluorescence revealed that magnolol interacted with the target, influencing the microenvironment around tyrosine residues, and circular dichroism explained a rearrangement of the secondary structure of α-glucosidase from the initial α-helix to the final conformation enriched with β-sheet and random coil. Docking studies provided support for the experimental results. Altogether, the data propose magnolol, for the first time, as a potential α-glucosidase inhibitor and add further evidence to the inhibitory role of luteolin.

Comparative Evaluation of the Antiglycation and Anti-α-Glucosidase Activities of Baicalein, Baicalin (Baicalein 7-O-Glucuronide) and the Antidiabetic Drug Metformin

“…To study the type of interaction between α–glucosidase and baicalein, the plot of enzyme activity ( v ) versus α–glucosidase enzyme concentration was obtained ( Figure 7 C), suggesting a concentration–dependent reversible interaction since all straight lines obtained at different concentrations of baicalein pass through the origin of the axes, and their slope decreased with increasing concentrations of the inhibitor. Previous research showed similar behavior for other natural compounds, for example, luteolin, morin, magnolol, and α–mangostin [ 48 , 50 , 51 , 52 ]. Furthermore, the type of baicalein inhibition was also estimated with Michaelis–Menten and Lineweaver–Burk plots ( Figure 8 A,B) obtained using different substrate concentrations (0.5, 1.0, 1.5 and 2.0 mM p NPG), while maintaining constant enzyme concentration (0.05 µM).…”

In Vitro Alpha-Glucosidase Inhibitory Activity and the Isolation of Luteolin from the Flower of Gymnanthemum amygdalinum (Delile) Sch. Bip ex Walp.

“…It was found to contribute to the effect of alpha-glucosidase inhibitory activity [ 13 ], but to date, there are still no reports on luteolin in G. amygdalinum ’s inhibitory effect against alpha-glucosidase. A previous report showed that luteolin has a non-competitive inhibition mechanism type [ 24 ]. Luteolin can also be found in Vernonia cinera , but its bioactivity is shown to be anti-inflammatory [ 12 ].…”

Flavonoids as dual-target inhibitors against α-glucosidase and α-amylase: a systematic review of in vitro studies

“…83 although chalconaringenin could not achieve a specific IC50 value toward α-amylase even at the concentration of 100 µM, the introduction of either prenyl or geranyl substituent significantly increased the inhibitory activity of this compound indicating the importance of these groups toward the inhibition manner of this chalcones. Moreover, his study also showed that the introduction of the geranyl group (131) increased the inhibitory potency by 20 times and 4 times, compared with desmethylxanthohumol (123), against α-glucosidase and α-amylase, respectively. As an effort to evaluate the anti-diabetic activities of the chalcone derivatives, 28 chalcones and 13 chalcone analogues have been synthesized and assessed for their IC50 value toward the two enzymes by Rocha et al (2019).…”

“…Luteolin (30) exhibits a similar inhibition profile on both enzymes but to a lesser extent of consent on αglucosidase. 15 out of 25 recorded findings 69,111,112,114,117,118,120,123,124,[127][128][129][130][131][132] showed stronger activity on α-glucosidase than acarbose, in contrast with the remaining 10 studies, 39,57,58,79,116,[133][134][135][136] making a 6:4 conflict. There was greater unity in the results of α-amylase inhibition, 39,137,138 confirming a moderate but generally weaker activity than acarbose on α-amylase (IC50 ranging from 14.57 µM to 1 mM).…”