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• Fluorescence,3D,Syn,UV–vis,FT-IR,Mol.Docking affirmed BSA-LVG interaction. • BSA intrinsic fluorescence was quenched by LVG via static mechanism. • LVG binding altered BSA native conformation. • Site probing, Mol.Docking revealed LVG at interface of BSA subdomains IIA & IIIA. • ASC, SAL suppressed BSA binding affinity for levonorgestrel. Serum proteins generally help to transport and distribute drug molecules within the body. In this study, the binding characteristics of bovine serum albumin (BSA) with levonorgestrel (LVG), an emergency contraceptive pill, and the influences of ascorbic acid (ASC) and salicylic acid (SAL) on the binding behaviour and protein structure were elucidated using multi-spectroscopic techniques and molecular docking. The results showed that levonorgestrel decreased BSA intrinsic fluorescence via static quenching mechanism. Binding constant (K a) values for BSA-LVG complexes were 103 to 104 M-1, indicating their high stabilities. Site probing/docking analysis indicated LVG bound between BSA subdomains IIA and IIIA. UV–visible absorption, Fourier Transform-Infrared and 3D fluorescence spectroscopies affirmed LVG-induced changes in BSA structure, especially in α-helix and β-sheet contents. ASC and SAL influenced BSA conformation for LVG binding and reduced the K a values by 3.37 and 5.43-folds, respectively. LVG altered the microenvironments of tyrosine residues, interacted with Arg-217, Lys-221, Val-292, Glu-443 etc. within the binding domains. The process was spontaneous (ΔG<0), entropy driven (TΔS>ΔH) and involved van der Waals forces and hydrogen bonding. The findings of the study offered details on the binding interaction between BSA and LVG, and also indicated that prior intake of ASC or SAL could suppress the binding affinity of BSA for levonorgestrel. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Kinetics, fluorescence, UV–Vis, FT-IR, Mol. Docking affirmed α-amylase-CA interaction. • CA inhibited α-amylase activity by a mixed inhibition, K ic < K iu ; with moderate IC 50. • AMY intrinsic fluorescence was quenched by CA via static mechanism. • CA binding altered AMY native conformation. • CA suppressed Advanced Glycation End-products (AGEs) formation. The quest to suppress complications associated with diabetes mellitus is ever increasing, while food additives and preservatives are currently being considered to play additional roles besides their uses in food enhancement and preservation. In the present study, the protective prowess of a common food preservative (citric acid, CA) against advanced glycation end-products (AGEs) formation and its binding interaction mechanism with α-amylase (AMY), an enzyme linked with hyperglycemia management, were examined. Enzyme inhibition kinetics, intrinsic fluorescence, synchronous and 3D fluorescence spectroscopies, ultraviolet–visible (UV–Vis) absorption spectroscopy, Fourier transform-infrared (FT-IR) spectroscopy, thermodynamics, and molecular docking analyses were employed. Results obtained showed that citric acid decreased α-amylase activity via mixed inhibition (IC 50 = 5.01 ± 0.87 mM, K ic = 2.42 mM, K iu = 160.34 mM) and suppressed AGEs formation (IC 50 = 0.795 ± 0.001 mM). The intrinsic fluorescence of free α-amylase was quenched via static mechanism with high bimolecular quenching constant (K q) and binding constant (K a) values. Analysis of thermodynamic properties revealed that AMY-CA complex was spontaneously formed (ΔG < 0), entropy driven (TΔS > ΔH), with involvement of electrostatic forces. UV–Vis, FT-IR and 3D fluorescence spectroscopies affirmed alterations in α-amylase native conformation due to CA binding interaction. CA interacted with His-101, Asp-197, His-299, and Glu-233 within AMY active site. Our findings indicated that CA could impair formation of AGEs and interact with α-amylase to slow down starch hydrolysis; vital properties in management of type 2 diabetes complications. [ABSTRACT FROM AUTHOR]

Obesity is a global health problem characterized by excessive fat deposition in adipose tissues and can be managed by targeting pancreatic lipase (PL) activity. In the present study, we investigated the in vitro antioxidant and anti-obesity potentials of methanolic leaf extract of Justicia carnea (MEJC) using lipase inhibition kinetics model. In silico evaluations of MEJC bioactive compounds as potential drug-like agents and inhibitors of PL were also investigated using SwissADME prediction tool, semi-empirical quantum mechanics(SQM), molecular electrostatic potential(MEP) and molecular docking analysis. Gas chromatography-mass spectrometry(GC–MS) revealed presence of campesterol, stigmasterol, beta-amyrin etc. MEJC scavenged reactive species and inhibited PL activity via a mixed inhibition pattern (K i = 107.69 μg/mL; K ii = 398.00 μg/mL) with IC 50 > orlistat's IC 50. Molecular docking of GC–MS identified compounds with porcine PL showed compounds 8,10,12 and 14 having high PL-binding affinity and similar binding pose with orlistat. Hydrophobic interactions and van der Waals forces were predominantly involved in the ligands' interactions with some key catalytic site amino acid residues (Ser-153,His-264). Compounds 10 , 12,13 and 14 indicated high drug-likeness, bioavailability, electronegativity, E LUMO -E HOMO energy gaps and MEP. Our findings show that MEJC is a rich natural source of antioxidant and anti-obesity agents which could be optimized for development of new anti-obesity drugs. [Display omitted] • Kinetics,SQM, MEP, Molecular docking gave evidence of lipase interaction with MEJC. • MEJC exhibited antioxidant properties. • MEJC inhibited pancreatic lipase by mixed inhibition pattern. • Compounds 10 , 12,13 and 14 showed high drug-likeness and chemical reactivity. • MEJC could be a potential source of novel lipase inhibitors. [ABSTRACT FROM AUTHOR]

The present study investigated the antioxidant and in vitro antidiabetic capacities of Justicia carnea aqueous leaf extract (JCAE) using α-amylase inhibition model. α-Amylase binding-interaction with JCAE was also investigated using fluorescence spectroscopy and molecular docking. Phytochemical screening and Gas Chromatography-Mass Spectrometry (GC–MS) analysis indicated presence of bioactive compounds. Phenolic (132 mg GAE/g) and flavonoid contents (31.08 mg CE/g) were high. JCAE exhibited high antioxidant capacity and effectively inhibited α-amylase activity (IC 50 , 671.43 ± 1.88 μg/mL), though lesser than acarbose effect (IC 50 , 108.91 ± 0.61 μg/mL). α-Amylase intrinsic fluorescence was quenched in the presence of JCAE. Ultraviolet-visible and FT-IR spectroscopies affirmed mild changes in α-amylase conformation. Synchronous fluorescence analysis indicated alterations in the microenvironments of tryptophan residues near α-amylase active site. Molecular docking affirmed non-polar interactions of compounds 6 and 7 in JCAE with Asp-197 and Trp-58 residues of α-amylase, respectively. Overall, JCAE indicated potential to prevent postprandial hyperglycemia by slowing down carbohydrate hydrolysis. Unlabelled Image • UV–vis, FT-IR and fluorescence provide evidence of α-amylase interaction with JCAE. • JCAE inhibited α-amylase activity and quenched α-amylase intrinsic fluorescence. • Microenvironments of tryptophan residues near α-amylase active site were altered. • Compounds 6 and 7 in JCAE showed highest binding affinities to α-amylase. • JCAE could be a potential source of novel α-amylase inhibitors. [ABSTRACT FROM AUTHOR]