Alkyl caffeates improve the antioxidant activity, antitumor property and oxidation stability of edible oil.

Jun Wang,Fu-An Wu,Fang-Qin Wang,Fei Pang,Shuang-Shuang Gu,Xiang-Yang Wu,Hong-Sheng Cui,Na Pang,Stephan Neil Witt

doi:10.1371/journal.pone.0095909

Abstract

Caffeic acid (CA) is distributed widely in nature and possesses strong antioxidant activity. However, CA has lower solubility in non-polar media, which limits its application in fat-soluble food. To increase the lipophilicity of natural antioxidant CA, a series of alkyl caffeates were synthesized and their antioxidant and antitumor activities were investigated. The antioxidant parameters, including the induction period, acid value and unsaturated fatty acid content, of the alkyl caffeates in edible oil were firstly investigated. The results indicated that alkyl caffeates had a lower DPPH IC50 (14–23 µM) compared to CA, dibutyl hydroxy toluene (BHT) and Vitamin C (24–51 µM), and significantly inhibited four human cancer cells (SW620, SW480, SGC7901 and HepG2) with inhibition ratio of 71.4–78.0% by a MTT assay. With regard to the induction period and acid value assays, methyl and butyl caffeates had higher abilities than BHT to restrain the oxidation process and improve the stability of edible oil. The addition of ethyl caffeate to oil allowed maintenance of a higher unsaturated fatty acid methyl ester content (68.53%) at high temperatures. Overall, the alkyl caffeats with short chain length (n<5) assessed better oxidative stability than those with long chain length. To date, this is the first report to the correlations among the antioxidant activity, anticancer activity and oxidative stability of alkyl caffeates.

Highlights

Synthetic liposoluble antioxidants are still widely used in the edible oil industry because of their efficient antioxidizability
This result indicated that the alkyl caffeates were potent antioxidants because they had higher DPPH scavenging compared to BHT and Vitamin C (VC), which are known commercial antioxidants
The antioxidant activity, antitumor property and oxidation stability of edible oil with added alkyl caffeates were investigated in the present study

Summary

Introduction

Synthetic liposoluble antioxidants are still widely used in the edible oil industry because of their efficient antioxidizability. Fruits and vegetables, numerous hydroxycinnamic acids are found, including caffeic acid (CA) [4], p-coumaric acid [5] and ferulic acid [6]. Among these hydroxycinnamic acids, increasing interest has been focused on CA because of its broader biological activities, including antioxidative [2], antimicrobial [7] and antitumor [8] activities. As an efficient antioxidant, the lower solubility of CA in non-polar media limits its application in fat-soluble food, especially in various edible oils [10,11]. Alkyl caffeates are more likely to be applied in oily food as antioxidants [13] because alkyl caffeates possess even higher antioxidative activity as antioxidants [14]

Methods

Results

Conclusion