Antioxidant properties in a non-polar environment of difluoromethyl bioisosteres of methyl hydroxycinnamates

MARTINEZ M. D.; LUNA L.; TESIO A. Y.; FERESIN G. E.; DURAN F. J.; BURTON G.

JOURNAL OF PHARMACY AND PHARMACOLOGY

PHARMACEUTICAL PRESS-ROYAL PHARMACEUTICAL SOC GREAT BRITIAN

Año: 2016 vol. 18 p. 233 - 244

0022-3573

Objectives Many natural antioxidants have poor pharmacokinetic properties that impair their therapeutic use. For hydroxycinnamic acids (HCAs) and other phenolic antioxidants, their major drawback is their low lipophilicity and a rapid metabolism. The difluoromethyl group may be considered as a ?lipophilic hydroxyl? due to its hydrogen bond donor and acceptor properties; this prompted us to assess it as a bioisosteric replacement of a phenolic hydroxyl for increasing the lipophilicity of HCAs.Methods Six difluoromethyl-substituted methyl cinnamates (4a-c, 5a-c) related to caffeic acid were synthesized and their antioxidant activity evaluated by chemical (FRAP, DPPH scavenging, inhibition of b-carotene bleaching, at 1?200 lM), electrochemical (differential pulse voltammetry, cyclic voltammetry) and cell-based (inhibition of lipid peroxidation in erythrocytes, at 1 and 50 lM) assays.Key findings Analogues 4a-c and 5a-c were inactive in FRAP and DPPH assays and only those containing a free phenolic hydroxyl (4a and 5a) exhibited electrochemical activity although with high redox potentials. Compounds 4a,b and 5a,b were active in the inhibition of b-carotene bleaching assay and all analogues inhibited lipid peroxidation in the human erythrocytes assay.Conclusions Lipophilic difluoromethyl-substituted cinnamic esters retain radical scavenging capabilities that prove useful to confer antioxidant properties in a non-polar environment.