MATERIALS AND METHODS: Curcumin and its analogues were subjected to docking using PDE4A, PDE4B, PDE4C and PDE4D as the targets. A data set comprising 18 analogues of curcumin, was used as ligands for docking of PDE4 subtypes. Curcumin was used as the standard for comparison. Docking was performed using AutoDock Vina 1.1.2 software integrated in LigandScout 4.1. During this process water molecules were removed from proteins, charges were added and receptor structures were minimised by applying suitable force fields. The docking scores were compared, and the selectivity of compounds for PDE4B over PDE4D was calculated as well.
RESULTS: All curcumin analogues used in the study showed good binding affinity with all PDE4 subtypes, with evident selectivity towards PDE4B subtype. Analogue A11 provides the highest binding affinity among all ligands.
CONCLUSION: Curcumin and analogues have moderate to strong affinity towards all PDE4 subtypes and have evident selectivity towards PDE4B. The Oxygen atom of the methoxy group plays a key role in PDE4B binding and any alterations could interfere with the binding. Tetrahydropyran side chain and heterocyclic rings are also suggested to be helpful in PDE4B binding.
METHODS: The quantification of the bioactive compounds was conducted using ultra-high-performance liquid chromatography multiple reactions monitoring tandem mass spectrometry (UHPLC-MS/MS-MRM) technique. The effect of the extract on CYP2C9 and CYP3A4 activities was determined using a fluorometric screening kit according to the manufacturer's instructions.
RESULTS: The three bioactive compounds were detected and quantified in the aqueous leaf extract. Results showed that the content of luteolin-7-O-glucuronide (47 μg/mg) was the highest followed by luteolin-7-O-glucoside (3.5 μg/mg) and 1,5-O-dicaffeoylquinic acid (1.07 μg/mg). The extract showed an inhibitory effect on CYP3A4 and CYP2C9 enzyme activities in control and diabetic rats.
CONCLUSIONS: The UHPLC-MS/MS-MRM method is sensitive and reliable for the quality control of V. amygdalina leaf extract. The inhibitory effect of the extract suggests that concomitant use of V. amygdalina leaf preparations with conventional drugs metabolized and eliminated from the body by CYP3A4 and CYP2C9 enzymes may lead to possible interaction.
METHODS: Diabetic rats were randomly assigned to four groups, with six rats in each group. Group 1 was administered distilled water. Group 2 was administered V. amygdalina aqueous leaf extract alone. Group 3 was administered metformin alone. Group 4 was co-administered V. amygdalina extract plus metformin. Blood was collected at predetermined intervals, and plasma metformin levels were measured with liquid chromatography. The area under the curve (AUC0-t), maximum plasma concentration (Cmax), time to reach Cmax (Tmax), half-life (t1/2), and clearance (CL), were calculated based on noncompartment analysis. The effect of the extract on CYP2C9, CYP3A4, and UGT activities was determined using a Fluorometric Screening Kit.
RESULTS: The combined treatment altered the pharmacokinetic parameters of metformin. The Tmax increased from 90±0.18 min to 180±0.13 min and the Cmax, increased from 0.91±0.32 μg/mL to 2.153±0.28 μg/mL. Additionally, the AUC(0-t) increased from 118.25±1.37 μg min mL-1 to 301.006±1.96 μg min mL-1 and the t1/2 increased from 34.69±0.61 min to 101.321±0.55 min. However, the CL rate was decreased. The extract inhibited CYP3A4 and CYP2C9 enzyme activities.
CONCLUSIONS: The alteration of pharmacokinetic parameters by the extract suggests potential herb-drug interactions.