Contents lists available at ScienceDirect Carbohydrate Polymers journal homepage: www.elsevier.com/locate/carbpol Research paper Anti-proliferative activity of a purified polysaccharide isolated from the basidiomycete fungus Paxillus involutus Ankush Barad a,1 , Sebastian Mackedenski a,1 , Wai Ming Li a,1 , Xiao Jie Li c , Bryan Chu Chwen Lim a , Faran Rashid a , Linda E. Tackaberry b , Hugues B. Massicotte b , Keith N. Egger b , Kerry Reimer a , Peter C.K. Cheung c , Chow H. Lee a, ⁎ a Chemistry Program, University of Northern British Columbia, Prince George, British Columbia, Canada b Ecosystem Science and Management Program, University of Northern British Columbia, Prince George, British Columbia, Canada c Food and Nutritional Sciences Program, School of Life Sciences, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China ARTICLE INFO Keywords: Paxillus involutus Polysaccharide Growth inhibition Mushroom British Columbia ABSTRACT A growth-inhibitory polysaccharide (GIPinv) was purified using size-exclusion and ion-exchange chromato- graphy from the fourth sodium hydroxide extraction step of a fungus found in British Columbia. The fungus was genetically identified as a member of the Paxillus involutus complex. GIPinv has an average molecular weight of 229 kDa and is a heteroglycan composed of glucose (65.9%), galactose (20.8%), mannose (7.8%), fucose (3.2%) and xylose (2.3%). GC–MS methylation analysis suggests that GIPinv has mixed linkages in the backbone con- taining (1 → 6)-Gal (25.5%), (1 → 4)-Glc (18.3%), (1 → 6)-Glc (8.3%), (1 → 3)-Glc (5.3%) and (1 → 2)-Xyl (4.5%). GIPinv has branching points at (1 → 2, 6)-Man (8.6%) and (1 → 3, 6)-Man (4.9%) having unsubstituted fucose (8.3%) and glucose (16.3%) as terminal sugars. GIPinv had growth-inhibitory activity against several cancer cell lines and triggered apoptosis. GIPinv should be further explored as a potential anti-cancer agent and a unique polysaccharide. 1. Introduction Fungi are a common and popular source of natural medicinal compounds that date back thousands of years (Wasser, 2014). Yet, it has been estimated that there are at least 150,000 macrofungi world- wide and, of these, only about 10% have been described (Wasser, 2014). This indirectly implies that fungi represent a major and largely untapped source of potentially powerful new pharmaceutical natural products. To our knowledge, besides our recent studies on British Columbia (BC) fungi (Smith et al., 2017), there had been only two reported stu- dies on the chemistry and bio-activity of native fungi found in the forests of Canada (Ming, Chilton, Fogarty, & Towers, 2002; Van et al., 2009). The first study reports on a new compound in Ganoderma ap- planatum collected from BC forests, but no insight is given as to whether the compound has biological activity (Ming et al., 2002); the second study shows anti-inflammatory effects of Inonotus obliquus collected from northern Manitoba, but no compound characterization was pro- vided (Van et al., 2009). Canada, and especially BC due to its high ecological diversity, is home to thousands of different fungi that have not been investigated for their potential medicinal value. Given this expected high diversity of untapped fungal species, coupled with the array of ecosystems and plant host relationships, we hypothesize that many unidentified biologically active novel compounds exist in mac- rofungi growing in northern BC. To this end, we have begun to explore medicinal properties of fungi native to BC, focusing first on three bio- assays that are relevant to cancer: growth-inhibitory, immuno-stimu- latory and anti-inflammatory activities (Smith et al., 2017). Compared to other genera, there have been relatively few studies on the bio-activity and chemical analysis of the genus Paxillus; to date, only four reports are available (Habtemariam, 1996; Lee et al., 2003; Lee, Jung, Kim, Rhee, & Yun, 2009; Wang et al., 2013). The ethyl acetate extract from P. involutus has been documented to be cytotoxic to a number of different cell lines (Habtemariam, 1996) while a lectin https://doi.org/10.1016/j.carbpol.2017.11.058 Received 21 August 2017; Received in revised form 19 October 2017; Accepted 15 November 2017 ⁎ Corresponding author at: Chemistry Program, University of Northern BC, 3333 University Way, Prince George, BC V2N 4Z9, Canada. 1 These authors contributed equally to this work and should be considered co-first authors. E-mail addresses: Ankush.Barad@alumni.unbc.ca (A. Barad), Sebastian.Mackedenski@alumni.unbc.ca (S. Mackedenski), mlidoudou@yahoo.ca (W.M. Li), lixiaojie@link.cuhk.edu.hk (X.J. Li), chuchwen@gmail.com (B.C.C. Lim), Faran.Rashid@alumni.unbc.ca (F. Rashid), tackaberry.linda@gmail.com (L.E. Tackaberry), hugues.massicotte@unbc.ca (H.B. Massicotte), keith.egger@unbc.ca (K.N. Egger), kerry.reimer@unbc.ca (K. Reimer), petercheung@cuhk.edu.hk (P.C.K. Cheung), chow.lee@unbc.ca (C.H. Lee). Carbohydrate Polymers 181 (2018) 923–930 Available online 16 November 2017 0144-8617/ © 2017 Elsevier Ltd. All rights reserved. T