Catechin Contents of Foods Commonly Consumed in The Netherlands. 1. Fruits, Vegetables, Staple Foods, and Processed Foods Ilja C. W. Arts, †,‡ Betty van de Putte, † and Peter C. H. Hollman* ,† State Institute for Quality Control of Agricultural Products (RIKILT), Wageningen, The Netherlands, and Department of Chronic Diseases Epidemiology, National Institute of Public Health and the Environment (RIVM), Bilthoven, The Netherlands Catechins, compounds that belong to the flavonoid class, are potentially beneficial to human health. To enable epidemiological evaluation of these compounds, data on their contents in foods are required. HPLC with UV and fluorescence detection was used to determine the levels of (+)-catechin, (-)- epicatechin, (+)-gallocatechin (GC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECg), and (-)-epigallocatechin gallate (EGCg) in 24 types of fruits, 27 types of vegetables and legumes, some staple foods, and processed foods commonly consumed in The Netherlands. Most fruits, chocolate, and some legumes contained catechins. Levels varied to a large extent: from 4.5 mg/kg in kiwi fruit to 610 mg/kg in black chocolate. (+)-Catechin and (-)-epicatechin were the predominant catechins; GC, EGC, and ECg were detected in some foods, but none of the foods contained EGCg. The data reported here provide a base for the epidemiological evaluation of the effect of catechins on the risk for chronic diseases. Keywords: Catechins; flavanols; flavonoids; fruits; vegetables; legumes; chocolate INTRODUCTION Observational studies show that fruits and vegetables protect against cancer and cardiovascular diseases (Law and Morris, 1998; Ness and Powles, 1997; Steinmetz and Potter, 1996). An important question is which compounds might be responsible for this protective effect. Flavonoids, secondary plant metabolites with antioxidant activity, are potentially protective com- pounds. The effects of flavonoids on the cancer process, the immune system, and hemostasis have been reported in cell systems and animals (Middleton and Kan- daswami, 1994). The average total intake of flavonoids in the United States was estimated to be 1 g/day. Catechins (Figure 1), one of the six classes of flavonoids, contributed one-fifth of the total estimated intake (Kuhnau, 1976). Catechins are the principal components of tea; they make up 3-10% of black tea solids and 30- 42% of green tea solids (Balentine et al., 1997). Epide- miological studies have shown that tea may reduce the risk for certain cancers (Kohlmeier et al., 1997; Blot et al., 1996), coronary heart disease, and stroke (Tijburg et al., 1997). However, the protective effect of tea is not undisputed. Catechins are also present in fruits and vegetables, and this may partially account for the ambiguity in the epidemiological data on tea. Still, quantitative data on catechin contents of foods are, as yet, largely absent, incomplete, or unreliable. Herrmann and co-workers started in the 1970s with the analyses of catechins in fruits using thin-layer chromatography methods with spectrophotometric mea- surements (Berger and Herrmann, 1971; Mosel and Herrmann, 1974b; Sto ¨hr and Herrmann, 1975a,b). These methods have been used often since. Their major drawback is that they respond not only to catechins but also to other compounds, which may result in an overestimation of the catechin content (Solich et al., 1996; Sarkar and Howarth, 1976). Over the past 10 years, analytical methods have evolved and nowadays selective and sensitive HPLC methods are available. However, reported data on catechin contents of foods are incomplete and mostly limited to (+)-catechin and (-)-epicatechin. Other catechins may be important to human health as well. For example (-)-epigallocatechin * Address correspondence to this author at the State Insti- tute for Quality Control of Agricultural Products (RIKILT), P.O. Box 230, 6700 AE Wageningen, The Netherlands (telephone +31 317 475578; fax +31 317 417717; e-mail p.c.h.hollman@rikilt.wag-ur.nl). † State Institute for Quality Control of Agricultural Products (RIKILT). ‡ National Insitute of Public Health and the Environment (RIVM). Figure 1. Chemical structures of catechins: (I)R ) H(+)- catechin, R ) OH (+)-gallocatechin (GC); (II)R ) H(-)- epicatechin, R ) OH (-)-epigallocatechin (EGC); (III)R ) H (-)-epicatechin gallate (ECg), R ) OH (-)-epigallocatechin gallate (EGCg). 1746 J. Agric. Food Chem. 2000, 48, 1746-1751 10.1021/jf000025h CCC: $19.00 © 2000 American Chemical Society Published on Web 04/25/2000