Anne Bozack Quercetin Content in Spinach May 8 2006 Effect of Organic and Conventional Farming Practices on Quercetin Content in Spinach Spinacia oleracea Anne Bozack Abstract Positive stresses and limitations of nutrient accessibility inherent in organic systems may increase the biosynthesis of secondary metabolites relative to conventional systems Since many secondary metabolites have antioxidant capabilities the potential of agricultural conditions to increase their content in produce has implications for the health of individual consumers In particular the common antioxidant quercetin present in spinach Spinacia oleracea has antihistamine and anti tumor properties Due to the beneficial properties of this compound this study was designed to establish the influence of 5 treatments associated with organic and conventional farming on its content in spinach 1 organic soil 2 synthetic soil with supplemental fertilizers 3 synthetic pesticides 4 simulated herbivory and 5 synthetic herbicides The content mass per fresh weight of quercetin and its glycocides rutin and quercitrin were quantified with high pressure liquid chromatography HPLC Rutin and quercitrin were not detectable in any of the samples Quercetin was present with each of the treatments however its content did not differ significantly among them p 1 Anne Bozack Quercetin Content in Spinach May 8 2006 Introduction Over the twentieth century trends in agriculture have shifted production from local and small scale farms to global and corporate businesses Favored by economics of scale large production systems have turned to chemical solutions to increase productivity and alleviate ecological problems a praxis often upsetting natural systems through the use of synthetic insecticides and herbicides Francis 2004 Organic farming practices offer an alternative through the decreased use of chemical inputs Consumers driven by environmental and health concerns to select organic products have encouraged this movement Davies et al 1995 and caused the market to increase 40 fold between 1986 and 1996 Fisher 1999 Organic policy varies throughout the world Bourn and Prescott 2002 but generally includes a set of core regulations The United States Department of Agriculture USDA requires certification to meet minimum standards prohibiting the use of nearly all chemical pesticides and herbicides and mandating practices that improve soil condition and minimize erosion National Organic Program 2000 Studies have largely concluded that organic practices offer environmental benefits relative to conventional systems by increasing biodiversity decreasing nutrient leaching Hansen et al 2001 and increasing nutrient recycling Brandt and M lgaard 2001 However implications for human health are more equivocal Food Quality Comprehensive reviews have reached some broad conclusions regarding food quality although differences in study design and the variability inherent in agricultural systems contribute to ambiguous findings that are often difficult to interpret Benbrook 2005 Research suggests that relative to their conventionally produced counterparts organicallyproduced crops generally have lower nitrate levels Bourn and Prescott 2002 Brandt and M lgaard 2001 Woese et al 1997 higher dry matter content Bourn and Prescott 2002 Woese et al 1997 and fewer chemical residues Baker et al 2002 Woese et al 1997 Conclusions regarding mineral content are more varied with some studies stating no difference Woese et al 1997 and others reporting significantly higher levels of certain minerals in organic produce Bourn and Prescott 2002 Worthington 2001 Likewise studies addressing Vitamin C content report contrasting findings ranging from higher levels to no difference or lower levels Bourn and Prescott 2002 Woese et al 1997 Secondary Metabolites The growing field of research focusing on levels of secondary metabolites may offer additional insights about food quality p 2 Plants produce secondary Anne Bozack Quercetin Content in Spinach May 8 2006 metabolites primarily for defense hence many are stress induced through wounding pathogenic attack exposure to high levels of ultraviolet light the need for signaling insufficient nutrients or low temperatures Dixon and Palva 1995 Relative to conventional systems organic systems may increase the exposure of crops to such stresses thus inducing the synthesis of secondary metabolites Manach et al 2004 Different cultivars display larger variation in secondary metabolite levels than those attributed to cultivation methods Brandt and M lgaard 2001 While crucial to plant health some secondary metabolites like polyphenols and carotenoids may also offer benefits for humans by acting as antioxidants to prevent oxidative damage in cells and subsequent cancerous growth Benbrook 2005 Radical scavenging acids and enzymes are produced by the human body but dietary contributions augment the supply of antioxidants Johns 1999 Hindered by a variety of confounding factors studies linking health benefits to specific chemicals are difficult Brandt et al 2004 However some studies have associated polyphenol consumption with a decrease in the occurrence of chronic diseases including cardiovascular disease Kenkt et al 2002 most notably in women Mennen et al 2004 Arai et al 2000 some types of cancer asthma and type 2 diabetes Kenkt et al 2002 Quercetin the most abundant flavonoid in food Formica and Regelson 1995 is highly studied and has been linked to several health benefits attributed to its antihistamine Middleton et al 1981 and anti tumor properties Lamson and Brignall 2005 Lambert et al 2005 Specifically it has been associated with decreased rates of prostate cancer McCann et al 2005 possibly due to its inhibition of enzymes responsible for carcinogenesis Chaudhary and Willett 2006 However some animal models have shown no effect Lambert et al 2005 Akin to research regarding nutrient levels findings comparing antioxidant levels in conventionally and organically cultivated crops are variable and subject to numerous confounding factors Studies have reported a range of results including higher levels LombardiBoccia et al 2004 Asami et al 2003 Carbonaro et al 2002 no difference Mitchell unpublished data 2005 or lower levels Lombardi Boccia et al 2004 of specific antioxidants in some organic fruits and vegetables Some research has specifically addressed the content of the antioxidant quercetin One study reported higher levels in organic than conventional
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