Yogyakarta-Indonesia, 4-5 th December 2007 Chemical Engineering Department , Gadjah Mada University 14TH REGIONAL SYMPOSIUM ON CHEMICAL ENGINEERING 2007 ISBN 978-979-16978-0-4 ABSTRACT Dillenia indica leaves have a good potential to be used as natural antioxidant. The object of this research is to get the optimum extraction method to obtain antioxidant compounds from Dillenia indica leaves. The methods that compared are sonication, soxhlet, and high-pressure extraction. To determine the used solvent, the sample extracted by maceration method using ethanol, petroleum ether, and ethyl acetate for three leaves powder diameter (0.3, 0.5, and 0.8 mm). The phenolic content and antioxidant activity of extracts were measured by using Folin-Ciocalteu reagent and carotene bleaching assay, respectively. The study showed that 0.3 mm ethanol extract has both the highest total phenolic content and antioxidant activity. Using DPPH radical scavenging assay, it found that both ethanol and ethyl acetate extracts have radical scavenger activity while petroleum ether extract shows no activity. The assay using carotene-bleaching method showed that sonication method provided extract with highest antioxidant activity compared with soxhlet and high-pressure extraction method. On the contrary, high-pressure extraction method produced extract with highest total phenolic content, followed by sonication and soxhlet method. The comparison using statistical analysis ANOVA showed that total phenolic content of extracts affected by the extraction method and operating conditions performed. Keywords: dillenia indica, antioxidant, carotene bleaching, total phenolic content, ANOVA I. INTRODUCTION In Indonesia, Dillenia indica plant has a large distribution such as in Sumatera, Java, and Kalimantan. This plant has a good potential to be use as natural antioxidant. The previous study showed that the kernel of Dillenia indica has antioxidant compounds that identified as 1-Dotriacontanol and BHT [1]. This natural antioxidant compound can be used as alternative to replace the synthetic antioxidant that can be dangerous for human health. The object of this research is to get the optimum extraction method to obtain antioxidant compounds of Dillenia indica leaves. The methods that compared are sonication, soxhlet, and high pressure extraction. Preceding study performed to determine leaves powder diameter and the used solvent. In the preceding study, the sample extracted by maceration method using both polar solvent and non-polar solvent for various leaves powder diameter. The antioxidant activity of extracts was measured by carotene bleaching assay to know the capability of extracts as antioxidant. The antioxidant activity from a sample can be related with total phenolic content in extract. This compound has several functions such as singlet and triplet oxygen quenchers, free radical scavengers, peroxide decomposers, enzyme inhibitors, and synergists [2]. The results of each method will be compared by ANOVA (Analysis of Variance). II. MATERIALS AND METHODS Sample Dillenia indica leaves that collected from Chemical Engineering Department University of Indonesia environment were used as sample. The leaves washed and dried at room temperature in 14 days and then crushed into powder with blender. After that, leaves filtered with sieve analyzer to get homogeneous particles. COMPARISON OF ANTIOXIDANT ACTIVITY AND TOTAL PHENOLIC CONTENT OF Dillenia indica LEAVES EXTRACTS OBTAINED USING VARIOUS TECHNIQUES Rita Arbianti, Tania Surya Utami, Aji Kurmana, Andre Sinaga Department of Chemical Engineering, University of Indonesia, Indonesia arbianti@che.ui.edu ; nana@che.ui.edu