Furthermore, feruloylquinic acids are common phenolic acids found in coffee samples; they are an ester linkage between a quinic acid and a ferulic acid. Due to the fact that there are no commercial standards of this chlorogenic acid, three concentrations of ferulic acid were tested. The results showed that this compound might also have an important contribution to the antimutagenic activity of spent coffee (37–51% protection). Shishu and Kaur (2008) reported that the methoxy group on the phenyl ring is responsible for the antimutagenic activity of ferulic acid.