Biological activity of oleic acid and its primary amide: Experimental and Computational studies

Abstract

Oleic acid (OA), and its primary amide (PA) derivative synthesized using thionyl chloride and ammonia solution were tested against five pathogenic fungi (Fusarium solani, Sclerotium rolfsii, Rhizoctonia solani, Pyricularia oryzae and Drechslera oryzae) for their repellent activity. Toxicity of the compounds to termite was also determined. The estimated HOMO-LUMO energy gap and associated global parameters: global hardness and softness, chemical potential, electrophilicity, electronegativity, ionization potential, electron affinity and polarizability of the optimized structures of OA and PA were determined by Density Function Theory (DFT) using Becke-3-Lee Yankpar function (DFT-B3LY 631G*). The amide proved to be a good inhibitor of fungi and as well repelled the termite significantly between 20 % and 80 %. The PA also followed the same trend in the toxicity to termite with LC50 mg/g of 1.2 and OA with LC50 mg/g of 89. The lower HOMO-LUMO energy gap associated with high global softness (0.094), lower ionization potential (9.55), higher electron affinity (-1.02), higher polarizability (3.13), higher electrophilicity (-1.71) and lower electronegativity value (4.26) of PA is a strong indication of its high electron distribution and stronger activity than the OA. This is in reasonable agreement with the experimental results.    Keywords: Pathogenic, Optimized, HOMO-LUMO structure, Oleic acid, amide and Chemical potential.