Antioxidant components of pili

A known commercial crop in the Bicol Region [Philippines], Pili (Canarium ovatum Engl.), grows abundantly in Southern Luzon and parts of the Visayas and Mindanao. Recent study had shown that pili exhibited a relatively high antioxidant activity. This project aims to evaluate the potential of pili fruit as a possible source of natural antioxidant. In addition, isolation, purification and possible identification of the antioxidant components was also investigated. Differential solvent extraction was done to assess the antioxidant potential of both the pili pulp and pili nut. Aqueous solvents were used to extract the hydrophilic antioxidative components whereas non-polar solvents were used for the lipophlic fractions. The antioxidant activity of the pulp fractions ranged from 60.56% to 82.2% as a radical scavenger (non-site specific assay) and 47.78% to 66.11% as a metal chelator (site specific assay) using the deoxyribose system. Reducing power ranged from 91.02 to 96.50%. Lipid peroxidation assay revealed an antioxidant activity that ranged from 70.83 to 87.50% inhibition. The total phenolic content evaluated using Folin-Ciocalteu Assay ranged from 32.62-586.79 mg/100 g. Thin layer chromatography (TLC) revealed the presence of phenolic compounds in the different sub-fractions of pili nut and pulp. An anthocyanin from pili pulp with considerable antioxidant activity was identified as cyanidin based on TLC, UV/IR spectroscopy and HPLC. The amount of anthocyanin present is approximately 400 mg/100 g expressed as Cyanidin-Chloride. Aside from cyanidin, other phenolic compounds were also detected by TLC. Ferulic acid was identified as one of the phenolic compounds present in pili. Pili nut extracted with n-hexane gave an antioxidant activity of 75.56% and 57.78% for non-site and site specific assay, respectively. The total phenolic content of the methanolic extract from pili nut was 153.06 mg/100 g expressed as Catechin equivalent. HPLC analysis of the n-hexane extract revealed that vitamin E was a major constituent. The vitamin E content was 252.73 and 306.72 mg/100 g as alpha-tocopherol for pili nut and pili nut paring respectively. The extract was identified based on the retention time of the external standard using HPLC and was identified further by IR spectroscopy.