Carbohydrate Polymers 171 (2017) 292–299 Contents lists available at ScienceDirect Carbohydrate Polymers j ourna l ho me pa g e: www.elsevier.com/locate/carbpol New findings on green sweet pepper (Capsicum annum) pectins: Rhamnogalacturonan and type I and II arabinogalactans Georgia Erdmann do Nascimento, Marcello Iacomini, Lucimara M.C. Cordeiro ∗ Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, CP 19.046, CEP 81.531-980, Curitiba, PR, Brazil a r t i c l e i n f o Article history: Received 18 December 2016 Received in revised form 20 April 2017 Accepted 8 May 2017 Available online 11 May 2017 Keywords: Sweet pepper fruits Homogalacturonan Type I arabinogalactan Type II arabinogalactan Type I rhamnogalacturonan Pectins a b s t r a c t Polysaccharides were extracted from sweet pepper (Capsicum annum) with hot water and named ANW (9% yield). Starch was precipitated by freeze-thaw treatment, while pectic polysaccharides (8% yield) remained soluble and consisted of GalA (67.0%), Rha (1.6%), Ara (6.4%), Xyl (0.3%), Gal (6.7%) and Glc (4.4%). A highly methoxylated homogalacturonan (HG, degree of methylesterification of 85% and degree of acetylation of 5%), and type I and type II arabinogalactans (AG-I and AG-II) were observed in NMR analyses. These were fractionated with Fehling’s solution to give HG (5.5% yield) and AG fractions (0.6% yield). AG-I and AG-II were further separated by ultrafiltration. AG-II (0.2% yield) consisted of Ara (17.1%), Gal (36.0%), Rha (5.6%) and GalA (12.0%), had a molecular weight of 5.3 × 10 4 g/mol and methylation and 1 H/ 13 C HSQC-DEPT-NMR analyses showed that it was anchored in type I rhamnogalacturonan. This is the first study that reports the presence of AG-I and AG-II in sweet pepper fruits. © 2017 Elsevier Ltd. All rights reserved. 1. Introduction Sweet (bell) peppers are fruits known worldwide for their importance in human diet as a food or as a condiment. The species Capsicum annuum L (Solanaceae) refers not only to sweet pep- pers, but also to wax peppers, cayenne peppers, chili peppers, and jalapeno peppers. Sweet peppers are known as important sources of vitamin C (ascorbic acid), -carotene, other carotenoid pigments (such as lycopene and zeaxanthin), phytochemicals and polyphenols (Chun et al., 2005; Hallmann & Rembiałkowska, 2012). Carbohydrate is the main macronutrient present in green sweet peppers with 4.9 g and a total dietary fiber of 2.6 g per 100 g of wet weight (Taco, 2011). The monosaccharide analysis of non-starch polysaccharides has shown a high uronic acid con- tent which has been associated with large amounts of pectins in sweet pepper fruits (Lopez-Hernandez, Oruna-Concha, Simal- Lozano, Vazquez-Blanco, & Gonzalez-Castro, 1996; Paik et al., 2003; Villanueva-Suárez, Redondo-Cuenca, Rodríguez-Sevilla, & de las Heras Martínez, 2003). A pectic polysaccharide named capsicuman was recently characterized by Popov et al. (2011). It was extracted from fresh sweet pepper using a simulated gastric medium (saline solution containing hydrochloric acid at pH 1.5 and pepsin at 37 ◦ C ∗ Corresponding author. E-mail addresses: lucimaramcc@ufpr.br, lucimaramcc@gmail.com (L.M.C. Cordeiro). for 4 h) and was shown to consist of D-galacturonic acid (GalA, 74.0%), rhamnose (Rha, 1.6%), arabinose (Ara, 2.6%) and galac- tose (Gal, 2.4%) residues. The study revealed that an acetylated and methyl esterified homogalacturonan (HG) was the core of the capsicuman. This polysaccharide showed immunomodulatory activity by decreasing TNF- and increasing IL-10 secretion in LPS- stimulated whole blood in mice besides improving the survival of mice that were subjected to a lethal dose of LPS. In this study the chemical characterization of C. annuum polysac- charides was performed. In addition to capsicuman, we report the presence of type I arabinogalactan anchored in type I rhamno- galacturonan, as well as the isolation and detailed structural characterization of a type II arabinogalactan. 2. Materials and methods 2.1. Plant material Fresh green sweet pepper fruits (C. annuum L. cv Magali) were purchased from the organic sector of the municipal market in Curitiba, Paraná, Brazil, in April 2014 and September 2016. 2.2. Polysaccharide extraction and fractionation Seeds were removed manually with the aid of a knife and then the deseeded fruit with skin (1.7 kg) was freeze-dried and milled (136 g). The dried powder was submitted to extraction through http://dx.doi.org/10.1016/j.carbpol.2017.05.029 0144-8617/© 2017 Elsevier Ltd. All rights reserved.