1. Academic Validation
  2. Synthesis and cholinesterase inhibiting potential of A-ring azepano- and 3-amino-3,4-seco-triterpenoids

Synthesis and cholinesterase inhibiting potential of A-ring azepano- and 3-amino-3,4-seco-triterpenoids

  • Bioorg Chem. 2020 Aug;101:104001. doi: 10.1016/j.bioorg.2020.104001.
Oxana Kazakova 1 Irina Smirnova 2 Tatyana Lopatina 2 Gul'nara Giniyatullina 2 Anastasiya Petrova 2 Elmira Khusnutdinova 2 René Csuk 3 Immo Serbian 4 Anne Loesche 4
Affiliations

Affiliations

  • 1 Ufa Institute of Chemistry UFRC RAS, pr. Octyabrya 71, 450054 Ufa, Russian Federation. Electronic address: obf@anrb.ru.
  • 2 Ufa Institute of Chemistry UFRC RAS, pr. Octyabrya 71, 450054 Ufa, Russian Federation.
  • 3 Martin-Luther-University Halle-Wittenberg, Organic Chemistry, Kurt-Mothes-Str. 2, D-06120 Halle (Saale), Germany. Electronic address: rene.csuk@chemie.uni-halle.de.
  • 4 Martin-Luther-University Halle-Wittenberg, Organic Chemistry, Kurt-Mothes-Str. 2, D-06120 Halle (Saale), Germany.
Abstract

In this study, a series of A-ring azepano- and 3-amino-3,4-seco-derivatives were synthesized from betulin, oleanolic, ursolic and glycyrrhetinic acids aiming to develop new cholinesterase inhibitors. Azepanobetulin, azepanoerythrodiol and azepanouvaol were modified to give amide and tosyl derivatives, while azepano-anhydrobetulines and azepano-glycyrrhetols were obtained for the first time. Oleanane and ursane type 3-amino-3,4-seco-4(23)-en triterpenic alcohols were synthesized by reducing the corresponding 2-cyano-derivatives accessible from Beckmann type 2 rearrangements. The compounds were screened in colorimetric Ellman's assays to determine their ability to act as inhibitors for the Enzymes acetylcholinesterase (AChE, from electric eel) and butyrylcholinesterase (BChE, from equine serum). While most of these compounds were only moderate inhibitors for AChE, several of them were shown to be inhibitors for BChE acting as mixed-type inhibitors. Azepanobetulin 1, its C28-amide derivatives 7 and 8, azepano-11-deoxo-glycyrrhetol 12 and azepanouvaol 18 held inhibition constants Ki ranging between 0.21 ± 0.06 to 0.68 ± 0.19 μM. Thus, they were approximately 4 to 10 times more active than standard galantamine hydrobromide. For all of the compounds reasonably high docking scores for BChE were obtained being in good agreement with the experimental results from the enzymatic studies. As a result, A-ring azepano-triterpenoids were found to be new scaffolds for the development of BChE inhibitors.

Keywords

Acetylcholinesterase; Alzheimer’s disease; Azepane; Betulin; Butyrylcholinesterase; Glycyrrhetinic acid; Oleanolic acid; Triterpenoids; Ursolic acid.

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