Chemoenzymatic Synthesis and α-Glucosidase Inhibitory Activity of Dimeric Neolignans Inspired by Magnolol

J Nat Prod. 2017 May 26;80(5):1648-1657. doi: 10.1021/acs.jnatprod.7b00250. Epub 2017 May 12.

Abstract

A chemoenzymatic synthesis of a small library of dimeric neolignans inspired by magnolol (1) is reported. The 2-iodoxybenzoic acid (IBX)-mediated regioselective ortho-hydroxylation of magnolol is described, affording the bisphenols 6 and 7. Further magnolol analogues (12, 13, 15-17, 19-23) were obtained from eugenol (3), tyrosol (4), and homovanillic alcohol (5), through horseradish peroxidase (HRP)-mediated oxidative coupling and regioselective ortho-hydroxylation or ortho-demethylation in the presence of IBX, followed by reductive treatment with Na2S2O4. A chemoselective protection/deprotection of the alcoholic group of 4 and 5 was carried out by lipase-mediated acetylation/deacetylation. The dimeric neolignans, together with 1 and honokiol (2), were evaluated as inhibitors of yeast α-glucosidase, in view of their possible utilization and optimization as antidiabetic drugs. The synthetic analogues of magnolol showed a strong inhibitory activity with IC50 values in the range 0.15-4.1 μM, much lower than those of honokiol and the reference compounds quercetin and acarbose. In particular, a very potent inhibitory activity, with an IC50 of 0.15 μM, was observed for 1,1'-dityrosol-8,8'-diacetate (15), and comparable inhibitory activities were also shown by bisphenols 6 (0.49 μM), 13 (0.50 μM), and 22 (0.86 μM). A kinetic study showed that 15 acts as a competitive inhibitor, with a Ki value of 0.86 μM.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biphenyl Compounds / chemistry
  • Biphenyl Compounds / isolation & purification*
  • Biphenyl Compounds / pharmacology*
  • Eugenol / chemistry*
  • Eugenol / pharmacology
  • Hypoglycemic Agents / chemistry
  • Hypoglycemic Agents / pharmacokinetics*
  • Iodobenzenes
  • Iodobenzoates / chemistry*
  • Iodobenzoates / pharmacokinetics
  • Lignans / chemical synthesis*
  • Lignans / chemistry
  • Lignans / isolation & purification*
  • Lignans / pharmacology*
  • Molecular Structure
  • Phenylethyl Alcohol / analogs & derivatives*
  • Phenylethyl Alcohol / chemistry
  • Phenylethyl Alcohol / pharmacology
  • alpha-Glucosidases / chemistry*
  • alpha-Glucosidases / metabolism*

Substances

  • Biphenyl Compounds
  • Hypoglycemic Agents
  • Iodobenzenes
  • Iodobenzoates
  • Lignans
  • magnolol
  • honokiol
  • 4-hydroxyphenylethanol
  • o-iodoxybenzoic acid
  • Eugenol
  • alpha-Glucosidases
  • Phenylethyl Alcohol