Antimicrobial Activity of 4-Hydroxybenzoic Acid and trans 4-Hydroxycinnamic Acid Isolated and Identified from Rice Hull

Abstract

  Two antimicrobial substances in rice hull were isolated and identified as 4-hydroxybenzoic acid and trans 4-hydroxycinnamic acid by LC-MS, and ¹H- and ¹³C-NMR. An evaluation of 50% inhibition of growth (IC₅₀) revealed that the two substances had different inhibition profiles against various microorganisms. Most of the gram-positive and some gram-negative bacteria were sensitive to trans 4-hydroxycinnamic acid and 4-hydroxybenzoic acid at IC₅₀ concentrations of 100-170 and 160 μg/ml, respectively.