Published: March 04, 2011 r2011 American Chemical Society 3180 dx.doi.org/10.1021/jf104045k | J. Agric. Food Chem. 2011, 59, 3180–3185 ARTICLE pubs.acs.org/JAFC Properties of Chalconaringenin and Rutin Isolated from Cherry Tomatoes Rune Slimestad* ,† and Michel Verheul ‡ † Saerheim Research Centre, PlantChem, N-4353 Klepp Station, Norway ‡ Norwegian Institute for Agricultural and Environmental Research—Bioforsk Vest Saerheim, Postvegen 213, N-4353 Klepp Station, Norway ABSTRACT: Fresh cherry tomatoes cv. 'Susanne' contain more of the two flavonoids chalconaringenin (CN) and rutin than lycopene. Therefore some properties including antioxidant behavior of the flavonoids were studied. The two flavonoids were extracted from peel and isolated by use of different chromatographic methods. Molecular absorbtivities were found to be 26907 for CN and 20328 abs M -1 cm -1 for rutin. Both compounds exhibited properties as antioxidants through several assays, and rutin was found to be the strongest antioxidant except in one assay. None of the assays revealed pro-oxidative effects. As naringenin rather than CN is frequently reported as a tomato constituent, the stability of CN was investigated in order to detect potential ways of isomerization during sample preparation. CN isomerized slowly both under UVB radiation and in alkaline solutions. Thus, such factors do not explain the occurrence of naringenin in tomato samples. The deficiency in reports on CN may be explained by the similarity in chromatographic behaviors of CN and naringenin, and due to the fact that they have same molecular weights. KEYWORDS: Solanum lycopersicum L., chalconaringenin, rutin, molar absorptivities, isomerization, antioxidants, FRAP, ABTS, DPPH, Price and Butler, Folin-Ciocalteu, nitric oxide ’ INTRODUCTION Tomato is well recognized for its content of phytonutrients, especially the carotenoid lycopene. The fruit may also contain similar amounts of flavonoids, especially chalconaringenin (CN) and rutin (Figure 1). CN belongs to the primary class of flavonoids known as the chalcones. Most of the known flavonoid structures are metabolites from this class of flavonoids which is recognized as consisting of a C6-C3-C6 carbon system with- out the typical C-ring midstructure. Although its presence in tomato fruits was reported for the first time in 1980, 1 many publications report on naringenin though spectroscopic features points out CN to be the actual structure, e.g. 2 CN is a pale yellow compound, whereas its isomer, the flavanone naringenin, is colorless. Rutin (quercetin 3-rutinoside) is a flavonol. It has been known as a tomato constituent since 1931. 3 Due to its ability to quench free radicals, its content in tomato fruits receives attention within horticultural and biotech research. 4-9 Both CN and rutin are basically located in the tomato peel. It thus follows that small tomatoes give a higher content of these compounds per unit serving compared to greater fruits. Their amounts in cherry tomatoes have been reported to be as high as 200 mg 100 g -1 fresh weight (FW) which exceeds the content of lycopene in average fruits (3 mg 100 g -1 ). 10 Instability of CN might be one of the reasons that naringenin rather than CN is reported. To investigate the stability of CN during sample preparation, a study was performed to look for any factors that could possibly give naringenin as an artifact. More- over, little information is available with respect to spectrophoto- metric data as molar absorptivities of CN and rutin. Such features were therefore investigated. As the content of flavonoids in tomato in general is accepted to strongly contribute to the antioxidant status of the fruit, the radical quenching and redox ability of these major flavonoid structures were surveyed through several assays. ’ MATERIALS AND METHODS Plant Material. Cherry tomato plants cv. ‘Susanne’ with visible flowers were planted at a plant density of 3.0 plants m -2 on rock wool slabs (15 Â 7.5 Â 90 cm) on October 20, 2008, in greenhouse compart- ments at Bioforsk Vest Saerheim. Natural light was supplemented with light from high pressure sodium lamps (Philips SON/T 400 W), providing a photon flux density of 220 μmol m -2 -s -1 photosynthetic active radiation at plant height during 18 h day -1 . The temperature set points in the greenhouse were 25 °C at day and 18 °C at night, with venting at 25 °C. In the greenhouse, a water vapor pressure deficit of Figure 1. Chemical structures of the two most common flavonoids found in the cherry tomato cv. ‘Suzanne’: chalconaringenin and rutin. Received: October 16, 2010 Accepted: February 7, 2011 Revised: January 21, 2011