Bioactive Phytochemical Contents on Fruit Peel of Several Citrus Species

Abstract

Citrus fruits contain important sources of bioactive compounds, including antioxidants such as flavonoids and phenolic compounds that are beneficial for human health. These bioactive compounds also exist in non-edible fruit parts, like the peel. The research was conducted to evaluate these bioactive phytochemicals on the peels of different citrus species. The experiment was carried out from March to August 2018 at the citrus germplasm collection of the Indonesian Instrument Standard Assessment Institute for Citrus and Subtropical Fruits and The Central Laboratory of The Indonesian Instrument Standard Assessment Institute for Legumes and Tubers Crops. The steps of research methods included the preparation of extract samples, the determination of total flavonoids and phenol content, and the DPPH radical scavenging assay. The results showed that the bioactive content of the citrus peels of several citrus species was diverse among the studied citrus species. Tangerine citrus cv. Kintamani was observed to have a higher phenolic content. For flavonoid content, the peel of lime cv. Borneo had the highest and Mandarin cv. Satsuma showed the least. Higher DPPH radical-scavenging activity values were observed on Mandarin cv. Pachuan, tangerine cv. Kintamani, and pumello cv. Thn. The correlation between phenolic content and DPPH radical-scavenging activity was higher than that between phenolic-flavonoid and flavonoid-DPPH radical-scavenging activity, indicating the effect of active molecule structure on redox potential.