Evaluation of bactericidal effects of chlorogenic or hydroxycinnamic acid derivatives and soluble coffee under low pH or gastric acid conditions

Soluble coffee and chlorogenic acid (CQA) showed bactericidal effects on Salmonella spp. and Escherichia coli under low pH conditions simulating gastric juice. However, soluble coffee contains various hydroxycinnamic acid derivatives other than CQA. The aim of this study was to evaluate the bactericidal activities of hydroxycinnamic acid derivatives. We prepared 12 kinds of hydroxycinnamic acid derivatives from green coffee beans and applied them to the bactericidal test using Salmonella spp. at pH 3.0. These compounds, including dicaffeoylquinic and caffeoyl-feruloylquinic acids, showed similar specific bactericidal activities, which were several times greater than that of soluble coffee. The sum of the activities of these compounds explained about 9% and 140% of the total activities of a soluble coffee and green coffee beans, respectively. Although the bactericidal activities and the contents of these compounds in retail soluble coffee samples were measured, no relationship between the activity and the content was apparent.