Characterization and antioxidant properties of ethyl acetate fractions from pyroligneous acid obtained by slow pyrolysis of palm kernel shell

Abstract

Sustainable utilization of palm kernel shell biomass can be achieved by thermochemical conversion method of slow pyrolysis, which is economical and eco-friendly. Palm kernel shell biomass has unlimited potential as an alternative form of fossil fuels and source of value added chemicals. Pyroligneous Acid (PA) is found to contain phenolic compounds with antioxidant activity, which have various applications. However, the low concentration of the antioxidant phenols makes the production of chemicals and medicines from palm kernel shell less viable. A higher yield percentage can be obtained from fractionation, which can also simplify identification of compounds. The total phenolic contents (TPC) were determined using the Folin ciocalteau assay, antioxidant activities using DPPH and FRAP assays and GC-MS was used to characterize the chemical constituents of the fractions with phenolic activities. Optimum pyrolysis condition was achieved at 429 °C with a 40.44 % yield. The obtained results showed the presence of phenolic activity in all 23 different samples. The fractions with the highest phenolic activity yielded TPCs of 181.75 μg/mL ± 17.0, 174.95 μg/mL ± 0.39 and 181.76 μg/mL ± 15.54. These fractions also simultaneously exhibited high DPPH activity of 23.97%, 31.39% and 52.58% respectively. Sixteen different types of phenolic chemical compounds and their derivatives were also identified with up to 60% higher concentrations when compared to previous studies without fractionation. These results indicated that the proposed approach allows for higher percentage yield of viable, pure and natural alternatives for use as chemicals and medicines, while simultaneously reducing agricultural waste.