Effects of Novel Tacrine Derivatives on Mitochondrial Energy Metabolism and Monoamine Oxidase Activity—In Vitro Study Jana Hroudová 1,2 & Tereza Nováková 1 & Jan Korábečný 3,4 & Dávid Maliňák 1,3 & Lukáš Górecki 1,3 & Zdeněk Fišar 1 Received: 14 July 2020 /Accepted: 14 October 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020 Abstract The trends of novel AD therapeutics are focused on multitarget-directed ligands (MTDLs), which combine cholinesterase inhibition with additional biological properties such as antioxidant properties to positively affect neuronal energy metabolism as well as mitochondrial function. We examined the in vitro effects of 10 novel MTDLs on the activities of mitochondrial enzymes (electron transport chain complexes and citrate synthase), mitochondrial respiration, and monoamine oxidase isoform (MAO-A and MAO-B) activity. The drug- induced effects of 7-MEOTA-adamantylamine heterodimers (K1011, K1013, K1018, K1020, and K1022) and tacrine/7-MEOTA/6- chlorotacrine-trolox heterodimers (K1046, K1053, K1056, K1060, and K1065) were measured in pig brain mitochondria. Most of the substances inhibited complex I- and complex II-linked respiration at high concentrations; K1046, K1053, K1056, and K1060 resulted in the least inhibition of mitochondrial respiration. Citrate synthase activity was not significantly inhibited by the tested substances; the least inhibition of complex I was observed for compounds K1060 and K1053, while both complex II/III and complex IV activity were markedly inhibited by K1011 and K1018. MAO-A was fully inhibited by K1018 and K1065, and MAO-B was fully inhibited by K1053 and K1065; the other tested drugs were partial inhibitors of both MAO-A and MAO-B. The tacrine/7-MEOTA/6-chlorotacrine-trolox heterodimers K1046, K1053, and K1060 seem to be the most suitable molecules for subsequent in vivo studies. These compounds had balanced inhibitory effects on mitochondrial respiration, with low complex I and complex II/III inhibition and full or partial inhibition of MAO-B activity. Keywords Alzheimer’s disease . Cholinesterase inhibitors . Electron transport chain complexes . Mitochondrial respiration . Monoamine oxidase . Multitarget-directed ligands Introduction Alzheimer’s disease (AD) is the most common form of de- mentia characterized by the progressive decline of a variety of higher cortical functions [1]. In the early stages of AD, the most commonly recognized symptom is the inability to acquire new memories. As the disease progresses, symptoms include long-term memory loss, confusion, language break- down, moodiness, irritability, and aggression. Senile plaques formed by β-amyloid (Aβ) deposits and aggregates of hyperphosphorylated tau protein stand at the forefront of AD pathophysiology [2]. Other factors, including * Jana Hroudová hroudova.jana@gmail.com Tereza Nováková tereza.kalina@gmail.com Jan Korábečný korabecny.jan1@gmail.com Dávid Maliňák david.malinak@gmail.com Lukáš Górecki LukasGorecki@seznam.cz Zdeněk Fišar zfisar@lf1.cuni.cz 1 Department of Psychiatry, General University Hospital in Prague, First Faculty of Medicine, Charles University, Ke Karlovu 11, 120 00 Prague 2, Czech Republic 2 Institute of Pharmacology, General University Hospital in Prague, First Faculty of Medicine, Charles University, Albertov 4, 128 00 Prague 2, Czech Republic 3 Biomedical Research Centre, University Hospital Hradec Kralove, Sokolská 581, 500 05 Hradec Králové, Czech Republic 4 Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, Třebešská 1575, 500 01 Hradec Králové, Czech Republic Molecular Neurobiology https://doi.org/10.1007/s12035-020-02172-1