Enhancement of the antioxidant and skin permeation properties of eugenol by the esterification of eugenol to new derivatives

Edyta Makuch,Łukasz Kucharski,Robert Pełech,Wiktoria Duchnik,Anna Nowak,Andrzej Günther,Adam Klimowicz

doi:10.1186/s13568-020-01122-3

Abstract

The aim of the study was to determine the antioxidant activity and assess the lipophilicity and skin penetration of eugenyl chloroacetate (EChA), eugenyl dichloroacetate (EDChA), and eugenyl trichloroacetate (ETChA). Identification of the obtained products was based on gas chromatography (GC), infrared spectroscopy (FTIR/ATR), gas chromatography coupled with mass spectrometry (GC-MS), and the analysis of 13C-NMR and 1H-NMR spectra. The antioxidative capacity of the derivatives obtained was determined by the DPPH free radical reduction method, while the octanol/water partition coefficient (shake-flask method) was tested to determine the lipophilicity of these compounds. In the next stage of testing EDChA and ETChA–(compounds characterized by the highest degree of free radical scavenging), the penetration of DPPH through pig skin and its accumulation in the skin were evaluated. For comparison, penetration studies of eugenol alone as well as dichloroacetic acid (DChAA) and trichloroacetic acid (TChAA) were also carried out. The antioxidant activity (DPPH, ABTS, and Folin–Ciocalteu methods) of the fluid that penetrated through pig skin was also evaluated. The in vitro pig skin penetration study showed that eugenol derivatives are particularly relevant for topical application. The obtained derivatives were characterized by a high level of antioxidant activity estimated after 24 h of conducting the experiment, which indicates long-term protection against reactive oxygen species (ROS) in the deeper layers of the skin.

Highlights

Reactive oxygen species (ROS) are important factors in the ageing process that are formed during incomplete reduction of oxygen molecules in the respiratory chain
Research by the gas chromatography (GC) method showed that the process yielded eugenol esters as the main products with 100% selectivity, with eugenol conversion of 99.7% and 99.8%
Based on the results obtained by the gas chromatography coupled with mass spectrometry (GC-MS) method, in the esterification process of eugenol with chloroacetic acid chloride, one product was obtained with the following masses (m/z): 240 (73%), (24%), and (3%)

Summary

Introduction

Reactive oxygen species (ROS) are important factors in the ageing process that are formed during incomplete reduction of oxygen molecules in the respiratory chain. Antioxidants are compounds characterized by the ability to deactivate free radicals responsible for the ageing process of the body (Dhale et al 2007; Michalak et al 2014; Igielska-Kalwat et al 2015; Agati et al 2012; Zhao 2015; Suvarnakuta et al 2011; Li and Seeram 2010; Janiuk et al 2013). To assess their antioxidant properties, in vitro methods are mainly used, and these are based on two types of reactions: the HAT (hydrogen atom transfer) technique and the SET (single electron transfer) method. The quantitative analysis of antioxidant capacity is based on the change in absorbance of the test solution (Gulcin 2011; Molyneux 2004; Li et al 2011; Benzie et al 1996)

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