Use of HPLC in the determination of the molar absorptivity of 4’-geranyloxyferulic acid and boropinic acid

Natural prenyloxycinnamic acids were shown to exert in vitro and in vivo remarkable and valuable anti-cancer and anti-inflammatory effects. Among these, 4′-geranyloxyferulic acid [3-(4′-geranyloxy-3′-methoxyphenyl)- 2-trans-propenoic acid] was discovered as an efficient orally active chemopreventive agent of several types of cancer, and its structural analogue boropinic acid was shown to exert a valuable inhibitory effect both in vitro and in vivo against the growth of Helicobacter pylori. As a continuation of our chemical, chemico-physical, and pharmacological studies on these secondary metabolites, we report herein the comparison between traditional UV/Vis assays and HPLC-DAD methods for the determination of the molar absorptivity coefficient of 4′-geranyloxyferulic acid (ε310 = 12,950 and ε288 = 11,910 L mol-1 cm-1) and boropinic acid (ε310 = 13,510 and ε288 = 12,350 L mol -1 cm-1). Ferulic acid was merely used as a reference standard to test the possibility of the application of these two assays to the oxyprenylated compounds. The data reported in the present study will represent an essential aid for future studies aimed to better define the pharmacological profile and the mechanism of action of these compounds and are an important starting point to evaluate other natural products where standard powders are not available.