Research paper Design and development of molecular hybrids of 2-pyridylpiperazine and 5-phenyl-1,3,4-oxadiazoles as potential multifunctional agents to treat Alzheimer's disease Avanish Tripathi, Priyanka Kumari Choubey, Piyoosh Sharma, Ankit Seth, Prabhash Nath Tripathi, Manish Kumar Tripathi, Santosh Kumar Prajapati, Sairam Krishnamurthy, Sushant Kumar Shrivastava * Department of Pharmaceutical Engineering & Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi, 221005, India article info Article history: Received 6 July 2019 Received in revised form 14 September 2019 Accepted 15 September 2019 Available online 16 September 2019 Keywords: Alzheimer's disease Acetylcholinesterase (AChE) b-Secretase-1 (BACE-1) Ab aggregation Molecular hybridization Multi-functional agents abstract The diverse nature of Alzheimer's disease (AD) has prompted researchers to develop multi-functional agents. Herein, we have designed and synthesized molecular hybrids of 2-pyridylpiperazine and 5- phenyl-1,3,4-oxadiazoles. Biological activities of synthesized compounds suggested significant and balanced inhibitory potential against target enzymes. In particular, compound 49 containing 2,4-difluoro substitution at terminal phenyl ring considered as most potential lead with inhibition of acetylcholin- esterase (hAChE, IC 50 ¼ 0.054 mM), butyrylcholinesterase (hBChE, IC 50 ¼ 0.787 mM) and beta-secretase-1 (hBACE-1, IC 50 ¼ 0.098 mM). The enzyme kinetics study of 49 against hAChE suggested a mixed type of inhibition (Ki ¼ 0.030 mM). Also, 48 and 49 showed significant displacement of propidium iodide from the peripheral anionic site (PAS) of hAChE, excellent blood-brain barrier (BBB) permeability in parallel artificial membrane permeation assay (PAMPA), and neuroprotective ability against SH-SY5Y neuro- blastoma cell lines. Further, 49 also exhibited anti-Ab aggregation activity in self- and AChE-induced thioflavin T assay, which was ascertained by morphological characterization by atomic force micro- scopy (AFM). Moreover, in vivo behavioral studies signified learning and memory improvement by compound 49 in scopolamine- and Ab-induced cognitive dysfunctions performed on Y-maze and Morris water maze. The ex vivo studies suggested decreased AChE activity and antioxidant potential of com- pound 49, with good oral absorption characteristics ascertained by pharmacokinetic studies. © 2019 Elsevier Masson SAS. All rights reserved. 1. Introduction Several decades ago, scientists instigated to solve the mysteries of a dreadful neurodegenerative ailment known as Alzheimer's dis- eases (AD). However, the complex etiology of this multifactorial disorder amalgamated with its riddled pathology remains to be elucidated [1 ,2]. One of the most distressing characteristics of the AD is the alteration of cognitive functions that presently corresponds to 50 million cases throughout the world [3]. The calamitous aspect of Alzheimer's is dementia, which broadly covers numerous conditions manifested by the loss of mental capabilities [4]. Mostly the disease originates in the memory center (hippocampal region) of the brain and then progresses to other brain centers that regulate verbal, judgmental, and physical activities of the patient [5]. The hallmarks of the disease constitute heightened propensity to develop amyloid plaques and neurofibrillary tangles that contributes to the disruption of the neuronal transit system and subsequent cessation of communication between neurons [6]. The catastrophic disorder grabs up the investments of millions of sufferers', slices their memories, notches their independence, and finally rip-off their dignity by draining their capacity to handle their normal life [7]. AD is multifactorial progressive disorder, interconnected with several pathophysiological hallmarks such as decline in acetylcholine (ACh) levels [8], deposition and aggregation of amyloid-beta (Ab)[9], N- methyl-D-aspartate receptor (NMDAR) activation [10], tau hyper- phosphorylation and production of neurofibrillary tangles [11], inflammation of CNS and neuronal cells [12], gene transcription by CREB (cAMP response element-binding protein) signaling mecha- nisms [13] and oxidative stress [14]. * Corresponding author. E-mail address: skshrivastava.phe@itbhu.ac.in (S.K. Shrivastava). Contents lists available at ScienceDirect European Journal of Medicinal Chemistry journal homepage: http://www.elsevier.com/locate/ejmech https://doi.org/10.1016/j.ejmech.2019.111707 0223-5234/© 2019 Elsevier Masson SAS. All rights reserved. European Journal of Medicinal Chemistry 183 (2019) 111707