Synthesis, Crystal Structure and Biological Activity of 2-Hydroxyethylammonium Salt of p-Aminobenzoic Acid

p -Aminobenzoic acid ( p ABA) plays important roles in a wide variety of metabolic processes. Herein we report the synthesis, theoretical calculations, crystallographic investigation, and in vitro determination of the biological activity and phytotoxicity of the p ABA salt, 2-hydroxyethylammonium p -aminobenzoate (HEA- p ABA). The ability of neutral and anionic forms of p ABA to interact with TIR1 pocket was investigated by calculation of molecular electrostatic potential maps on the accessible surface area, docking experiments, Molecular Dynamics and Quantum Mechanics/Molecular Mechanics calculations. The docking study of the folate precursor p ABA, its anionic form and natural auxin (indole-3-acetic acid, IAA) with the auxin receptor TIR1 revealed a similar binding mode in the active site. The phytotoxic evaluation of HEA- p ABA, p ABA and 2-hydroxyethylamine (HEA) was performed on the model plant Arabidopsis thaliana ecotype Col 0 at five different concentrations. HEA- p ABA and p ABA acted as potential auxin-like regulators of root development in Arabidopsis thaliana (0.1 and 0.2 mM) and displayed an agravitropic root response at high concentration (2 mM). This study suggests that HEA- p ABA and p ABA might be considered as potential new regulators of plant growth.