Anti-inflammatory activities of phenolic compounds in fractionated pyroligneous acid from slow pyrolysis of palm kernel shell

Abstract

The significant growth in the oil palm industry in recent years in South-East Asia and particularly Malaysia, has subsequently led to the generation of a tremendous amount of oil palm biomass waste. Palm kernel shell (PKS), constitutes a major fraction of this waste and if not properly managed can result in pollution of the environment. PKS has the potential to be thermochemically converted into bio-char, gaseous products and liquids known as pyroligneous acid (PA). PA has been found to contain phenolic compounds and their derivatives, which various studies have shown to have antioxidant and anti-inflammatory effects. There were two main objectives of this research work. First, to determine a viable method of extracting phenolic compounds in sufficiently high concentrations. Second, to investigate a pharmacological mechanism of action through the cyclo-oxygenase (COX) and lipooxygenase (LOX) pathway of phenolic compounds produced from PA-PKS. A total of 40.44% of PA was obtained from the pyrolysis of PKS as optimum condition. Extraction of PA using ethyl acetate (CEPA) resulted in 112 fractions which were ultimately pooled into 23 sub-fractions based on thin layer chromatography (TLC) and similarity in the antioxidant activities. Gas chromatography-mass spectrometry (GCMS) analysis of the CEPA fraction having highest antioxidant activities showed much higher concentrations of phenolic compounds and its derivatives (around 20%) compared to phenol concentration in industrial PA. Further analysis of the CEPA subfractions also ascertained the mechanism of action of phenolic compounds and their derivatives. Determination on the pharmacological activity for CEPA resulted in IC50 values of 17.04 % for the COX assay and 5.25 % for LOX, which was higher than IC50 for aspirin (control experiment) with values of 19.70 % (COX) and 40.35 % (LOX) respectively. The Malondi-aldehyde assay indicate high efficiency of CEPA as lipid peroxidation agent. From the pyrolysis work, phenol concentration was shown to increase with dual inhibition of the COX and LOX pathways. As a conclusion, PKS was demonstrated to have the potential to be used as one of the raw materials for the production of highly valuable compounds.