Types of compound Type of study Study models Dose/concentration Assay type Findings/activity References Tacrine-benzoate (phenyl acetates or cinnamates) hybrid In-vitro AChE, from electric eel, BuChE, from equine serum 5.63 nM Ellman method Inhibit AChE with highest selectivity ratio against BuChE [114 ] 7-MEOTA-donepezil-like hybrids In-vivo Male Wistar rats 25.6, 12.3, 5.7, 5.2 mg/kg Water maze test, passive avoidance test Significant effect of the swim order indicating maintenance of learning ability [115 ] Tacrine-ferulic acid hybrids In-vitro AChE BuChE Spectrophotometric method Good inhibitory activity to both AChE and BuChE, better selectivity for AChE compared with tacrine [100 ] In-vitro Aβ (1–42) 20 μ M Thioflavin T-based fluorometric assay Similar inhibitory activity as curcumin and ferulic acid [100 ] Ferulic acid-tacrine-melatonin hybrids (FATMHs) In-vitro SH-SY5Y cells 1 μ M and 3 μ M Neuroprotection analyses Significant neuroprotection was observed against all toxic insults assayed [116 ] Tacrine-trolox, tryptoline hybrids In-vitro TcAChE from electric eel, eqBuChE (from equine serum) 49.31 nM 17.37 nM Ellman’s assay Hybrids with longer linker chain lengths show increased AChE inhibitory activities compared to the shorter ones [117 ] Tacrine-cinnamic acid hybrids In vivo Adult ICR mice 15 mg/kg Morris water Maze test Considerably ameliorated the cognitive impairment of the treated mice And was much better than tacrine [118 ] ALT & AST level test Did not show any hepatotoxicity at all the time points [118 ] In vitroIn vivo AChE, BuChE, Aβ (1–42) ICR mice 10.2 nM 6.3 nM 30 mg/kg Ellman’s Assay Thioflavin T-based fluorometric assay Morris water Maze test Cholinesterase inhibitory activities, amelioration of scopolamine-induced cognition impairment, preliminary safety in hepatotoxicity evaluation [119 ] (Benz)imidazopyridino tacrines In-vitro EeAChE eqBuChE μ MEllman protocol Nonhepatotoxic shows moderate and selective EeAChE inhibition [120 ] Tacrine-O-protected phenolics heterodimers In-vitro AChE, from electric eel, BuChE, from equine serum 3.5 μ M Ellman method Safe, nonhepatotoxic, potent, and selective inhibitor of hBuChE [121 ] Tacrine-resveratrol-fused hybrids In-vitro AChE, from electric eel, BuChE, from equine serum 8.8 μ M Ellman method AChE inhibition, Aβ self-aggregation modulation, anti-inflammatory, and immunomodulatory properties, high-predicted blood-brain barrier permeability, and low cytotoxicity [49 ] Tacrine-ferulic acid hybrids In-vitro Aβ (1–42) 20 μ M Thioflavin T-based fluorometric assay Inhibited amyloid β -protein self-aggregation by 65.49% [122 ] In-vitro AChE, from electric eel, BuChE, from equine serum 37.02 nM Ellman method Potent inhibitor against AChE and strong inhibitor against BuChE [122 ] In vivo Adult ICR mice 30 mg/kg Morris water maze test, serum ALT, AST test Ameliorated the cognition impairment and showed preliminary safety in hepatotoxicity evaluation [122 ] Tacrine-acridine hybrids In-vitro AChE, from electric eel, BuChE, from equine serum 7.6 pM 1.7 pM Ellman method More active inhibitor than tacrine [123 ] In-vitro Aβ (1–42) 50 μ M Thioflavin T (ThT) fluorescence assay 54.74% inhibition of Aβ aggregation [123 ] Tacrine-deferiprone hybrids In-vitro AChE, from electric eel 0.64 μ M Ellman method Control of cholinergic dysfunction, amyloid peptide aggregation, oxidative stress, and metal modulation [124 ] Tacrine, phenolic acid, and ligustrazine hybrids In-vitro AChE, from electric eel 3.9 nM Ellman method Potent inhibition activity towards cholinesterases (ChEs) [125 ] In-vitro — μ MDPPH assay Very potent peroxyl radical scavenging capacity [125 ] Cystamine-tacrine dimer In-vitro SH-SY5Y cell line 0.005-0.5 μ M MTT assay Enzymatic assay Fluorometric assay AChE and BChE inhibitor; activates kinase 1 and 2 (ERK1/2) and Akt/(PKB) pathways [92 ] Tacrine-trolox hybrid In-vivo Male Sprague-Dawley (SD) rats 6 mmol/100 g b. wt (AST) and (ALT) activity Introduction of trolox could reduce the hepatotoxicity of tacrine [93 ] In-vitro Electric eel, Ellman’s reagent, DTNB 9.8-23.5 nM 20.5-22.2 nM Ellman’s assay More potent inhibitory activity for BuChE than for AChE [93 ] PC12 cells 3.125 μ M and 6.25 μ M MTT assay Significantly inhibit cell death [93 ] Tacrine-propargylamine derivatives In-vitro Human neuroblastoma cell line, SH-SY5Y 10, 50, and 100 μ M MTT assay Nearly no effect on the viability of SH-SY5Y cells, lower cytotoxicity than tacrine [126 ] Tacrine-coumarin hybrids In-vitro hMAO-A, hMAO-B 0.24 μ M Fluorimetric method Selective MAO-B inhibitor [94 ] In-vitro eeAChE, hBuChE Ellman’s method Potent inhibitory action for AChE and BuChE [94 ] In-silico Recombinant hAChE — — Simultaneously bind to PAS and CAS and the mid-gorge site of AChE [94 ] In-vitro hAChE, hBuChE 38 nM 63 nM Ellman’s method Potent and selective inhibitory activities towards both hAChE and hBuChE [127 ] In-vitro A-β 1-40 peptide 1 μ M Thioflavin T assay Inhibit A-β 40 amyloid self-assembly [127 ] In-silico hAChE(1ACJ), hBuChE (4 BDS), β -secretase (BACE1) — AutoDock 4.2 and Vina Fingerprints studies showed 34 ligands to be effective in their docking binding energies and high binding natures [128 ] Tacrine-benzofuran hybrids In-vitro Recombinant hAChE and hBChE 0.86 nM 1.35 μ M Ellman’s assay Selectively inhibited hAChE, suppressed both hBACE-1 activity and β -amyloid aggregation [95 ] In-vivo ICR mice 20 μ mol/kg Morris water maze test Considerably ameliorated the cognition impairment of the treated mice [95 ] Tacrine/cysteine-conjugated compounds In-vitro Amyloid-β peptide 70 μ M Fluorescence assay Decreased Aβ 42 (40 μ M) self-aggregation [96 ] In-vitro Human neuroblastoma SH-SY5Y cells 2.5 μ M MTT assay Cell viability is not significantly affected after a 24-h treatment [96 ] TcAChE 0.30 μ M Ellman0s assay High inhibitory activity in submicromolar range [96 ] In-silico — — Molecular docking Target both the CAS and PAS of AChE [96 ] Tacrine-phenylbenzothiazole hybrids In-vitro AChE from electric eel Aβ (1–42) 0.15 μ M 40 μ M Modified method of Ellman’s assay Thioflavin T (ThT) assay Excellent AChE inhibitory activity and moderate inhibition values for amyloid-β (Aβ ) self-aggregation (27–44.6%) [129 ] Tacrine-1,2,4-thiadiazole derivatives conjugates In-vitro Human erythrocytes AChE equine serum BChE, porcine liver CES 17.1 μ M 44.8 μ M Ellman method Effectively inhibited cholinesterases with a predominant effect on (BChE), could block AChE-induced β -amyloid aggregation [130 ] Tacrine-hydroxamate derivatives In-vitro AChE BChE HDAC 0.12 nM 361.52 nM 0.23 nM Ellman method Fluorescence assay Potent and selective inhibition on ache, potent inhibition on HDAC, recognitive impairments inhibitory activity on Aβ 1-42 self-aggregation as well as disaggregation activity on preformed Aβ fibrils [47 ] Tacrine-pyrimidone hybrids In-vitro Murine AChE Recombinant human GSK-3β 51.1 nM 89.3 nM Ellman’s method with modification Possessed excellent dual AChE/GSK-3 inhibition both in terms of potency and equilibrium [48 ] In-vivo Female ICR mice 15 mg/kg Morris water maze (MWM) tests Displayed significant amelioration on cognitive deficits in scopolamine-induced amnesia mice [48 ] Tacrine(10)-hupyridone dimer In-vivo Wild-type (WT) mice 0.36 or 0.72 μ mol/kg Morris water maze (MWM) tests Long-term treatment of the compound could attenuate precognitive impairments in APP/PS1 transgenic mice [131 ] Tacrine and salicylamide conjugates In vitro AChE BChE 0.22 μ M 0.01 μ M Propidium iodide fluorescence Exhibited high dual anticholinesterase activity with selectivity towards BChE [132 ]
