Hydroxycinnamic acids are a class of aromatic acids and hydroxy derivatives of cinnamic acid. These compounds account for about one third of the phenolic compounds in human diets. They have gained a great interest because they are known to be potent antioxidants. In this study, the spectroscopic properties (absorbance and fluorescence) of several hydoxycinnamic acids such as caffeic acid, coumaric acid, ferulic acid and sinapic acid were determined at different pH conditions (pH 3, 7, 10, and 12). Results indicated that both absorbance and fluorescence spectra showed blue shift of the peak from pH 3 to pH 7 and then red shifted from pH 7 onwards. Emission intensity was observed to increase in ferulic and sinapic acid as pH increases, while caffeic acid only increases to a pH of 10. However, the intensity of coumaric acid decreases from pH 3 to pH 7, almost having the same intensity at a higher pH. Theoretical calculations on the absorbance agree with experimental results where there is a blue shift from pH 3 to pH 7 and then a red shift from pH 7 onwards.

Spectroscopic properties of hydroxycinnamic acids under acidic, neutral, and basic conditions

253rd National Meeting (2017)

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