O-alkylated quercetins with selective acetylcholinesterase and β-secretase inhibitions from Melicope glabra leaves, and their flavonols profile by LC-ESI-Q-TOF/MS

• Published in: Journal of functional foods Vol. 84; p. 104602
• Main Authors: Baiseitova, Aizhamal, Shah, Abdul Bari, Kim, Jeong Yoon, Ban, Yeong Jun, Kim, Jeong Ho, Nafiah, Mohd Azlan, Park, Ki Hun
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.09.2021; Elsevier
• Subjects: Acetylcholinesterase; Antioxidant; Melicope glabra; Pteleifolosin C; Pteleifolosin E; β-secretase; β-secretase; Melicope glabra; Acetylcholinesterase; Antioxidant; Pteleifolosin C; Pteleifolosin E
• ISSN: 1756-4646; 2214-9414
• DOI: 10.1016/j.jff.2021.104602

[Display omitted] •Quercetin derivatives (1-13) including the new (2) were isolated from M. glabra.•O-Alkylated quercetins were selective inhibitory potential toward hAChE and BACE1.•All compounds from M. glabra had a significant antioxidant potentials.•LC-ESI-Q-TOF/MS disclosed inhibitors as main metabolite of M. glabra leave extract. Intensive investigation of phytochemicals from edible Melicope glabra leaves provided a series of O-alkylated quercetins (1–13). The quercetin 1 bearing prenyl and methyl motif showed potent inhibition to human acetylcholinesterase (hAChE) with mixed type I mode, while quercetin was inactive. The position of methyl group was also a critical factor to hAChE inhibition: 1 (4′-O-methyl, IC50 = 12.7 μM) vs2 (3′-O-methyl, IC50 = 119 μM). Inhibitory potency was doubly confirmed with the binding affinity (KSV) based on fluorescence quenching. O-Methyl groups on quercetin were observed to influence β-secretase (BACE1) inhibition. Thus, O-methylated quercetins (4–6) displayed potential inhibitions against BACE1 with IC50 values of 1.3, 4.1, and 14.1 μM, respectively. All compounds (3–6) have noncompetitive mode to BACE1. Additionally, all quercetin derivatives (1–13) had antioxidant potentials against different radical sources (ABTS, ORAC and FRAP). The UPLC-ESI-Q-TOF/MS indicated that the leaves part had promising metabolites towards hAChE and BACE1 inhibitions, which are the most predominant phytochemicals.