Antioxidants, toxicity and nitric oxide inhibition properties of pyroligneous acid from palm kernel shell biomass

Abstract

Abstract: Huge volumes of lignocellulosic biomass residues generated from agricultural activities such as oil palm biomass pose great environmental threats if improperly treated. In this study, pyroligneous acid (PA) obtained from slow pyrolysis of palm kernel shell (PKS) were evaluated for its antioxidant activity via chemical assays, toxicity, and potential as anti-inflammatory agent based on nitric oxide (NO) inhibition activity. The PA was extracted using ethyl acetate (EA) and fractionated using column chromatography. Fractions 13–17 that contain highest total phenolic contents (866.84 ± 54.28 µg GAE/mg) were chosen for subsequent studies. Results obtained were as follows; DPPH—75.34 ± 3.40%, TEAC—1346.48 ± 5.29 μg Trolox/mg, FRAP—11.80 ± 0.41 mmol Fe(II)/mg, hydroxyl radical scavenging—IC50 270.34 ± 4.88 µg/mL, superoxide radical scavenging—IC50 472.32 ± 1.87 µg/mL, cytotoxicity after 24 h at less than 50 µg/mL—cell viability of ≥ 93.08% for RAW 264.7 macrophage cell and anti-inflammatory activity with NO production of 6.55% after 24 h at sample concentration of 25 µg/mL. From the GC–MS analysis, phenols and derivatives were identified as major compound (83.24%) followed by esters (11.23%), and ketones (5.53%). The present of phenolic compounds namely benzene-1,2-diol, catechol (35.01%), 1,3-dimethoxy-2-hydroxybenzene, syringol (23.81%), and other catechol derivatives can be attributed to the antioxidant and anti-inflammatory activities determined. This study has successfully demonstrated the potential use of PA obtained from PKS as alternative antioxidant and anti-inflammatory agent.