An unusual homoisoflavanone and a structurally-related dihydrochalcone from Polygonum ferrugineum (Polygonaceae) Silvia N. Lo ´pez a , Manuel Gonzalez Sierra b , Susana J. Gattuso c , Ricardo L. Furla ´n a , Susana A. Zacchino a, * a Farmacognosia, Facultad de Ciencias Bioquı ´micas y Farmace ´uticas, Universidad Nacional de Rosario, Suipacha 531 (2000), Rosario, Argentina b Instituto de Quı ´mica Orga ´ nica de Sı ´ntesis (IQUIOS, CONICET-UNR), Universidad Nacional de Rosario, Suipacha 531 (2000), Rosario, Argentina c Biologı ´a Vegetal, Facultad de Ciencias Bioquı ´micas y Farmace ´uticas, Universidad Nacional de Rosario, Suipacha 531 (2000), Rosario, Argentina Received 10 November 2005; received in revised form 24 April 2006 Available online 1 August 2006 Abstract The homoisoflavanone 5,7-dihydroxy-6-methoxy-3-(9-hydroxy-phenylmethyl)-chroman-4-one (1) and its structurally related 2 0 ,4 0 ,6 0 - trihydroxy-3 0 -methoxy-a-hydroxymethyl-b-hydroxy-dihydrochalcone (2) along with the known pashanone (3), flavokawin B (4) and car- damonin or alpinetin chalcone (5) pinostrobin (6) and 5,8-dimethoxy-7-hydroxychroman-4-one (7) were isolated from dry leaves of Polygonum ferrugineum (Polygonaceae). To our knowledge, this is the first report of the isolation of a homoisoflavanone from the Polyg- onum genus and the Polygonaceae family, and could be an important chemotaxonomic finding. In addition, the pattern of substitution of this homoisoflavanone is different from others previously reported. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Polygonum ferrugineum; Polygonaceae; Homoisoflavanone; Dihydrochalcone; Flavanones; Chalcones; 5,7-Dihydroxy-6-methoxy-3-(9-hydr- oxy-phenylmethyl)-chroman-4-one; 2 0 ,4 0 ,6 0 -Trihydroxy-3 0 -methoxy-a-hydroxymethyl-b-hydroxydihydrochalcone 1. Introduction The genus Polygonum (Polygonaceae), comprising about 300 species (Wang et al., 2005), is distributed worldwide in temperate climates, and is widely found in South America. It is well known for producing a variety of secondary metabolites including flavonoids (Sartor et al., 1999; Peng et al., 2003), triterpenoids (Duwiejua et al., 1999), anthra- quinones (Matsuda et al., 2001; Yim et al., 1998), couma- rins (Sun and Sneden, 1999), phenylpropanoids (Murai et al., 2001; Takasaki et al., 2001), lignans (Kim et al., 1994), sesquiterpenoids (Datta et al., 2000), stilbenoids (Nonaka et al., 1982), and tannins (Wang et al., 2005). Amongst them, flavonoids are the most common compo- nents found in Polygonum spp. and have previously been used as chemotaxonomic markers of the genus, playing an important role in the systematics of Polygonaceae spe- cies (Datta et al., 2002). Within the 21 Polygonum species growing in Argentina (Gattuso, 1998), Polygonum ferrugineum Wedd. common name caatay guazu ´, a native shrub found in swampy grounds in the north and center of the country, has not pre- viously been studied for its chemical composition. As a part of our ongoing project devoted to the phytochemical study of the Polygonum genus, we have isolated a novel homoisoflavanone (1) and a novel dihydrochalcone deriva- tive (2) structurally related to (1), along with five known compounds, three chalcones (3–5) and two flavanones (6 and 7). The present paper describes the isolation of compounds 1–7 and the structural characterization of the two new compounds 1 and 2. 0031-9422/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.phytochem.2006.06.018 * Corresponding author. Fax: +54 341 3375315. E-mail address: szaabgil@citynet.net.ar (S.A. Zacchino). www.elsevier.com/locate/phytochem Phytochemistry 67 (2006) 2152–2158 PHYTOCHEMISTRY