Carbohydrate Polymers 83 (2011) 600–607 Contents lists available at ScienceDirect Carbohydrate Polymers journal homepage: www.elsevier.com/locate/carbpol Extraction of antioxidant pectic-polysaccharide from mangosteen (Garcinia mangostana) rind: Optimization using response surface methodology Chee-Yuen Gan ∗ , Aishah A. Latiff Doping Control Centre, University Sains Malaysia, 11800 USM, Penang, Malaysia article info Article history: Received 6 August 2010 Accepted 11 August 2010 Available online 18 August 2010 Keywords: Extraction Mangosteen Garcinia mangostana Optimization Pectic-polysaccharide Response surface methodology abstract Box-Behnken design (BBD) was employed to optimize the incubator temperature (X 1 : 50–80 ◦ C), extrac- tion time (X 2 : 2–4 h) and pH (X 3 : 2–4) to obtain a high antioxidant pectic-polysaccharide yield with high uronic acid content and antioxidant activity from mangosteen rind. Analysis of variance showed that the contribution of quadratic model was significant for the extraction yield and antioxidant activity whereas linear model was significant for pectin content. Optimization study using response surface methodology was performed and 3D response surfaces were plotted from the mathematical model. Two optimal condi- tions were given: condition (1) X 1 = 80.0 ◦ C; X 2 = 3.93 h; X 3 = 2.45, and condition (2) X 1 = 67.7 ◦ C; X 2 = 3.67 h; X 3 = 2.00. These optimum conditions yielded pectic-polysaccharide of ∼12.0–12.4%, uronic acid content of ∼20.2–21.1 mg/g, and %DPPHsc/g extract of 225–252, respectively. Close agreement between experimen- tal and predicted values was found. This could therefore be applied in extraction of mangosteen-derived functional pectic-polysaccharide in industry. © 2010 Elsevier Ltd. All rights reserved. 1. Introduction Lignocellulosic biomass is the most abundant plant-derived materials (e.g. agricultural residues, herbaceous crops, forestry wastes, woods) that have been left behind by the agro-food indus- tries due to the modern agriculture practices that had increased food production yield tremendously and parallel to this is the amount of waste generated from this large scale cultivation. This occurrence has brought up a serious concern in environmental issues as well as the alternatives to solve the problems encoun- tered. Globally, part of these waste materials have been used for animal feed and fertilizer (Mamma, Kourtoglou, & Christakopoulos, 2008), however, a large portion of these materials is still deposited annually. In recent decades, lignocellulosic biomass has attracted attention in biorefinery process. It was suggested that this material could be the largest potential feedstock for bioethanol production (Huang, Ramaswamy, Tschirner, & Ramarao, 2008; Kim et al., 2010; Kszos, 2006). Apart from bioethanol, natural products should also be considered. Therefore, food, nutraceutical and pharmaceutical industries have come into place where the industries are search- ing for new ingredients from natural sources (Guerrero, Torres, & Nu˜ nez, 2008; Kasankala, Xue, Weilong, Hong, & He, 2007; Levigne, Ralet, & Thibault, 2002; Masmoudi et al., 2008; Wu, Cui, Tang, & Gu, 2007). ∗ Corresponding author. Tel.: +60 4 6595606x2682; fax: +60 4 6569869. E-mail address: mattgan81@yahoo.com (C.-Y. Gan). Apart from cellulose, all plant cell walls have a similar struc- ture that consists of pectins (also known as pectic-polysaccharides) (Lerouxel, Cavalier, Liepman, & Keegstra, 2006). These plant- derived materials are widely used as gelling agents, thickeners, stabilisers, emulsifiers and fat-substitutes, and are listed as ingre- dients in numerous food products (Rolin, Nielsen, & Glahn, 1998; Willats, Knox, & Mikkelsen, 2006). Citrus peels and apple pomace are currently the important sources of pectin manufacturing, whilst other potentially valuable sources remain largely unex- plored. Recent published work showed that Parkia speciosa pod could produce functional pectic-polysaccharide (Gan, Abdul Manaf, & Latiff, 2010a, 2010b). Wong, Alkarkhi, and Easa (in press, 2010) have also extracted this pectic-polysaccharides from durian rind and found that this extracted pectic-polysaccharide could act as biosorbent to remove heavy metal such as lead, nickel, and copper. Water-soluble pectin extracted from a durian rind was also found to have wound healing properties (Hokputsa et al., 2004). Other health effects of pectins, such as lowering cholesterol and serum glucose levels (Yamada, 1996; Behall & Reiser, 1986), inducing apoptosis in human colonic adenocarcinoma cells (Olano- Martin, Rimbach, Gibson, & Rastall, 2003) and anticancer activities (Yamada, Kiyohara, & Matsumoto, 2003), were also evident. Hence, this search for plant-derived biomaterials has therefore stimulated research interest in producing functional components from under- utilized bulk agro-waste, such as fruit peels. In the current study, mangosteen (Garcinia mangostana) rind was used. Mangosteen, known as “queen of fruits”, is cultivated in Southeastern Asia. The fruit is whitish colour with soft texture whereas the rind is firm and dark purple in colour. Traditionally, 0144-8617/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.carbpol.2010.08.025