Antioxidant Capacity of Berry Crops, Culinary Herbs and Medicinal Herbs

Herbs and berry crops have been shown to contain high levels of antioxidant compounds. These antioxidants are capable of performing a number of functions including acting as free radical scavengers, peroxide decomposers, singlet and triplet oxygen quenchers, enzyme inhibitors, and synergists. The different antioxidant components found in herbs and berry crops provide protection against harmful free radicals and have been associated with lower incidence and mortality rates of cancer and heart disease, in addition to a number of other health benefits. Herbs have been used for many purposes including medicine, nutrition, flavorings, beverages, and industry. Since prehistoric times, herbs have been the basis for nearly all medicinal therapy until synthetic drugs were developed in the Nineteenth Century. Today herbs are still found in 40 percent of prescription drugs. Culinary herbs also have been grown and used for their ability to enhance and complement the flavors of a wide variety of foods. Even though a variety of herbs are known to be remarkable sources of phenolic compounds, data on the composition and antioxidant activities of herbs and berry crops are insufficient. We found herbs and berry crops to contain a number of healthful phytochemicals such as vitamin E, vitamin C, bata carotene, flavonoids, phenolic acids and are an effective and potential source of natural antioxidants. The results from this presentation will be useful to plant breeders, other researchers, and the general public who are interested in the antioxidant potentials of various herbs and berry crops as dietary supplements. INTRODUCTION Antioxidants are compounds that can delay or inhibit the oxidation of lipid or other molecules by inhibiting the initiation or propagation of oxidizing chain reactions (Velioglu et al., 1998). The antioxidant activity of phenolic compounds are mainly due to their redox properties, which can play an important role in adsorbing and neutralizing free radicals, quenching singlet and triplet oxygen or decomposing peroxide (Osawa, 1994). In general there are two basic categories of antioxidants, natural and synthetic. Recently, interest has been increasing considerably in finding naturally occurring antioxidants for use in foods or medicinal materials to replace synthetic antioxidants which are being restricted due to their carcinogenicity (Ito et al., 1983). Berry fruits, and herbs contain high levels of antioxidant compounds, which provide protection against harmful free radicals and have been associated with a number of health benefits (Ames et al., 1993; Cao et al., 1996; Velioglu et al., 1998; Wang et al., 1996). Herbs have been used for a large range of purposes including medicine, nutrition, flavorings, beverages, dyeing, repellents, fragrances, cosmetics, charms, smoking, and industrial uses. Since prehistoric times, herbs were the basis for of nearly all medicinal therapy until synthetic drugs were developed in the nineteenth century. Today herbs are still found in 40 percent of prescription drugs (Smith and Winder, 1996). Culinary herbs have been grown and used for hundreds of years, and they are becoming increasingly popular in the United States for their ability to enhance and complement the flavors of a wide variety of foods (Hacskaylo, 1996). A variety of herbs are known to be sources of phenolic compounds and various herbs along with fruits contain numerous phytochemicals in addition to phenolic Proc. XXVI IHC – Asian Plants Eds. Jung-Myung Lee and Donglin Zhang Acta Hort. 620, ISHS 2003 Publication supported by Can. Int. Dev. Agency (CIDA) 462 compounds, such as nitrogen compounds, carotenoids, and ascorbic acid (Larson, 1988; Velioglu et al., 1998). Many of these phytochemicals possess significant antioxidant capacities (Larson, 1988). Diets rich in fruits, vegetables and herbs significantly reduce the incidence and the mortality rates of cancer, cardiovascular disorders, and other degenerative diseases caused by oxidative stress. Eating fruits, vegetables and herbs also reduces blood pressure, enhances the immune system, detoxifies contaminants and pollutants, and reduces inflammation (Ames et al., 1993; Larson, 1988; Velioglu et. al., 1998). Therefore, modification of dietary and lifestyle habits can lead to significant improvements in human health. This paper summarizes the antioxidant capacities of various berry fruits and herbs and the factors which affect their antioxidant activities. This paper also suggests some strategies for establishing new research and production paradigms for enhancing antioxidant capacity and nutrient quality. DIETARY ANTIOXIDANTS The phytochemicals in plant tissues responsible for antioxidant capacity can largely be attributed to the phenolics, anthocyanins, carotenoids, and other flavonoid compounds. Fruits, vegetables and herbs contain many of these components. Anthocyanins and Other Flavonoids In the typical U.S. diet, daily intake of anthocyanins is approximately 180-215 mg/day, and represents the largest group of phenolic compounds in the human diet (Kühnau, 1976). The content of anthocyanins in fruit of blackberry, blueberry, cranberry, raspberry, strawberry and boysenberry range from 200 to 4950 mg.kg of fresh weight. In blueberries, the anthocyanin content is 10 to 200 times of the quercetin (Prior et al., 1998). The anthocyanins are glycosides and acylglycosides of anthocyanidins. Some common anthocyanidins have varying different hydroxyl or methyl substitutions in their basic structure, flavylium. Over 250 naturally occurring anthocyanins exist, and are differentiated further by their Oglycosylation with different sugar substitutes (Francis, 1989). Glucose, rhamnose, xylose, galactose, arabinose, and fructose are the most common sugars substituted on the aglycon (anthocyanidin). The common anthocyanins are either 3or 3, 5-glycosylated. Free radical scavenging properties of the phenolic hydroxy groups attached to ring structures are responsible for the strong antioxidant properties of the anthocyanins (Rice-Evans and Miller, 1996; Wang et al., 1997). They help reduce damage caused by free-radical activity and low-density lipoprotein oxidation, platelet aggregation, and endothelium-dependent vasodilation of arteries (Heinonen et al., 1998; Rice-Evans and Miller, 1996). The other flavonoids, flavones (e.g., apigenin, luteolin, diosmetin), flavonols (e.g., quercetin, myricetin, kaempferol), and their glycosides are the most common compounds. They occur in nearly all our common fruits, vegetables and herbs. These flavonoids have been showed antioxidant and antitumor properties and also have applications as antibiotics, antidiarrheal, antiulcer and anti-inflammatory agents as well as in the treatment of diseases such as hypertension, vascular fragility, allergies, hypercholesterolemia (Kühnau, 1976; Larson, 1988; Rice-Evans and Miller, 1996; Heinonen et al., 1998). Carotenoids Carotenoids are found in many fruits and vegetables such as carrots, dark leafy greens, orange and yellow vegetables and orange fruits. They are comprised of a set of several hundred pigmented, fat soluble antioxidants. The most abundant carotenoids in fruits and vegetables are α-carotene, β-carotene, lycopene, lutein, zeazanthin, and β-cryptozanthin. These carotenoids account for more than 90% of the carotenoids present in the human diet (Gerster, 1997). The nature of the carotenoids affects it bioavailability and lutein is five times more readily available in the human body than β-carotene (van het Hof et al., 1999). Combination of fatty foods with carotenoid-rich fruits and vegetables enhanced carotenoids uptake. Recent studies have shown that the bioavailability of lycopene from tomato has increased dramatically by heat treatment in the presence of oil