Chapter Three - Antioxidant Activity and Protecting Health Effects of Common Medicinal Plants
Introduction
Since the prehistoric time, many medicinal plants were used in folk medicine. They have been used all over the world for thousands of years as natural medicines possessing therapeutic and other pharmacologic effect. Today, according to the World Health Organization (WHO), as many as 80% of the world's people depend on traditional medicine for their primary health-care needs. The preliminary results of a study on behalf of WHO have shown that the number of individuals using medicinal plants is large and on the increase, even among young people (WHO, IUCN, & WWF, 1993).
Medicinal plants or parts of these plants (leaves, rhizomes, roots, seeds, flowers) can be utilized in different forms such as fresh crude form and preparations as teas, decoctions, powdered plant material, or extracted forms of medicinal agents (juices, water or alcohol extracts, tinctures, essential oils, resins, balsams).
In the pharmaceutical industry, medicinal plants are valued for their chemical constituents—active substances such as polyphenols and flavonoids, glycosides, alkaloids, and tannins, which may be used as agents in the synthesis of drugs. Besides medical purposes, they could be important in nutrition as they contain many biologically active substances such as vitamins or components of essential oils. They are also used in food industry and cosmetics due to their preservative effect because of the presence of antioxidants and antimicrobial constituents and due to the flavoring and dyeing properties of some medicinal plants. Utilization of many medicinal plants for culinary purposes is also very popular in the everyday diet, to flavor various meals and foods. They are widespread in Eastern region and in Western countries too.
In recent decades, in the developed world, especially in the United States, a strong desire for things that are natural has appeared. Even if the natural and artificial exemplars are specified to be chemically identical, a majority of people who prefer natural continue to prefer it (Rozin et al., 2004). Therefore, medicinal plants as natural source could be of great economic importance not only because of their utilization in medicine but also as food additives (e.g., as antioxidants due to their strong antioxidant effect) extracted from natural sources.
Medicinal plants are generally known and popular for a number of health benefits such as decreasing of blood pressure, prevention of cardiovascular diseases, or reducing the risk of cancer also due to their antioxidant activity.
Medicinal plants contain high levels of antioxidants that can delay or inhibit the oxidation of lipids or other molecules. Many lipid-oxidation products are known to interact with biological materials to cause cellular damage, so oxidation process has been associated with chronic diseases such as cancer.
General recommendation for the consumers is to increase the consumption of foods containing antioxidants. Thus, the regular sufficient intake of these foods (fruits, vegetables, teas, wine, medicinal plants, and their preparations) could be a good possibility to support the health condition. However, the effective physiological relevance of their intake is meanwhile uncertain as many studies are mainly based on in vitro assays that do not necessarily reflect the human physiological mechanisms in vivo (Becker, Nissen, & Skibsted, 2004). Therefore, the effects of dietary antioxidants in vivo should be studied intensively to know their physiological effects.
This chapter is focused on the characterization of oxidative processes and antioxidants, profile of medicinal plant antioxidants, their benefits, and protecting health effects of common medicinal plants.
Section snippets
Implication of oxidation processes in foods
Foods contain lipids, proteins, saccharides, and vitamins that can be attacked by free radicals causing their oxidation. Oxidation, occurring especially in lipids and lipid-containing foods, is generally resulting in the deterioration in nutritional and sensory quality of foods. Therefore, it is a problem of great economic importance in the food production.
Oxidation decreases the nutritional quality and safety after food processing and culinary use (deep-fried foods) by the formation of
Antioxidants in Medicinal Plants
Numerous epidemiological studies have shown an inverse relationship between the intake of natural antioxidants from plant products and the incidence of some diseases because dietary plant antioxidants are capable of removing free radicals. Plant materials, such as medicinal plants (herbs, spices), could be promising sources of effective antioxidants. Among them, phenolic compounds, flavonoids and vitamins, exhibit potent antioxidant activities.
Many constituents of plants may contribute to their
Medicinal Plants as Sources of Antioxidants
Medicinal plants are plants or parts of plants (leaves, flowers, seeds, rhizomes, roots, stems, and barks) used for therapeutic or medical benefit. Besides benefits for medicinal and pharmaceutical industry, they can be utilized in food industry (food antioxidants, antimicrobial components, functional food components, nutritional supplements, flavoring, and dyeing compounds), cosmetic industry (antioxidant and antimicrobial components, flavoring, and dyeing compounds), and perfumery (aroma
Antioxidant Activity of Medicinal Plants
The antioxidant properties of plants, such as medicinal plants, herbs, and spices, and their constituent compounds have been widely studied. The research in this area has been led at least partially by several branches of industry seeking for natural protecting compounds.
The antioxidant activity (AA) of medicinal plants depends on each plant (variety, environmental conditions, harvesting methods, postharvest treatment, and processing), and composition and concentration of present antioxidants.
Protecting Health Effects of Medicinal Plants
Medicinal plants and their products are used worldwide for thousands of years due to their health effects (anti-inflammatory, antioxidant, antibacterial, digestive, antispasmodic, cholagogue, carminative, diuretic, hypolipidemic, sedative, enhancing the function of the immune system as well as anticancer, antitumor activity, etc.) and a key role in preventing various diseases such as cardiovascular diseases, gastrointestinal disorders, inflammatory diseases, and cancer initiation. According to
Conclusion
Aromatic plants have been extensively studied due to their antioxidant and antimicrobial effects and other positive health benefits such as prevention of cardiovascular diseases, atherosclerosis, inflammation, or reducing the risk of cancer. To commonly used medicinal plants with antioxidantactivity belong plants from several families, especially Lamiaceae (rosemary, sage, oregano, marjoram, basil, thyme, mints, balm), Apiaceae (cumin, fennel, caraway), and Zingiberaceae (turmeric, ginger).
The
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