Limonoid has been isolated from orange seeds of Citrus microcarpa Bunge using extraction and partitioning methods. It is a yellowish-white crystal with a melting point of 276-277 oC. Based on the phytochemical analysis and FTIR spectroscopy, 1H NMR and compared with the literature, the compound is limonin which is a triterpenoid. The purpose of this study was to determine the structure and evaluate antioxidant activity of the limonin. The antioxidant activity by DPPH obtained IC50 value of

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... in was 199.18 ppm. Whereas, the test antioxidant activity by FRAP method using a comparative solution of ascorbic acid showed that there was an increasingly blue color change, which meant that antioxidant activity was stronger with activity value of 11.88 mgAAE /g sample.