MY PJ WORK

CHAPTER ONE

INTRODUCTION

1.1 Background of Study

The products of biological compounds oxidation, by interaction with important biomolecules, can upset cell homeostasis and act cytotoxically, resulting in different diseases like tumors, heart failure, and cataract, brain dysfunction (Lobo et al., 2010).  Antioxidants are the substances able to prevent or inhibit oxidative processes in human body as well as in plant products (Aguilar et al., 2011). The natural antioxidants are a stable part of nutrition as they occur in almost all edible plant products. Polyphenols are the most numerous group of antioxidant components and they are present in fruits and vegetables, their products, leguminous plants, grains, teas, herbs, spices and wines (Barros et al., 2011). Consumption of food containing a lot of polyunsaturated fatty acids raised the significance and usage of substances that protect them against oxidation. The antioxidant supplementation is a generally accepted method of prolonging the stability and storage life of food products, in particular products that contain fat (Aguilar et al., 2012). However, the artificial compounds with antioxidant properties, like butylated hydroxyanisol (BHA) and butylated hydroxytoluene (BHT), have a limited allowance for food due to their potential carcinogenicity (Berker et al., 2007).  The growing demand for natural antioxidants observed in food and cosmetic industries forces the search for new sources of these compounds. Numerous scientific investigations point at consecutive rich sources of antioxidants, especially among plants.

Antioxidants are compounds that help delay and inhibit lipid oxidation and when added to foods tend to minimize rancidity, retard the formation of toxic oxidation products, help to maintain the nutritional quality and increase their shelf life (Moon and Shibamoto, 2009). Antioxidants can eliminate free radicals and other reactive oxygen and nitrogen species, and these reactive species contribute to most chronic diseases. It is hypothesized that antioxidants originating from plants may work as antioxidants in their own right in vivo, as well as bring about beneficial health effects through other mechanisms, including acting as inducers of mechanisms related to antioxidant defense, longevity, cell maintenance and DNA repair (Baur et al., 2006). Research focused on natural foods and medicinal plants has grown since evidence of their potential interference in the production of reactive oxygen species was uncovered. These reactive oxygen species play an important role in the progression of a great number of pathological disturbances such as inflammation, atherosclerosis, stroke, heart disease, diabetes mellitus, multiple sclerosis, cancer, Parkinson’s disease, Alzheimer’s disease, etc. They are also responsible for the nutritional value losses, as well as aroma, taste and texture degradation (Galve et al., 2005). Polyphenols are the most numerous group of antioxidant components, and they are present in plant, fruits and vegetables. Polyphenols are present in a variety of plants utilized as important components of both human and animal diets. Fruit and vegetables provide the best polypharmacy against the development of a chronic disease, considering that they contain a vast array of antioxidant components such as polyphenols. Polyphenols make a major contribution to free radical scavenging capacities (Lin et al., 2008). There is a direct relationship between antioxidant activity and total phenolics content in selected herbs, vegetables and fruits. Polyphenols are a broad family of naturally-occurring physiologically-active nutrients. They can be divided into four subgroups. The first group is called bioflavonoids. The next two groups are related compounds of bioflavonoids and are called anthocyanins and proanthocyanidins. The last group is called xanthones. Phenolic compounds act as antioxidants with mechanisms involving both free radical scavenging and metal chelation. They have ideal structural chemistry for free radical-scavenging activities, and have been shown to be more effective antioxidants in vitro than vitamins E and C on a molar basis (Arts et al., 2005; George et al., 2005).

The interest in natural antioxidants and oxidative stress conditions, especially in countries with limited access to conventional treatment method of diabetes, is inadequate. There is an increased demand for natural products with anti-diabetic activity due to the side effects associated with the use of insulin and oral hypoglycemic agents (Lotito and Fraga, 2000).  The World Health Organization has also recommended and encouraged the use of natural products for the management of diabetes. Natural antioxidants such as flavonoids and polyphenols are believed to possess antioxidant properties due to their reducing and chelating capabilities. Flavonoids and polyphenols are secondary plant metabolites that are widely distributed in plants leaves and other parts in plants with free radical scavenging abilities (Surai, 2003).

Phytochemicals are bioactive compounds that have been associated with the protection of human health against chronic degenerative diseases. These bioactive compounds are also known as secondary metabolites (Kirshnaiah et al., 2007). There are two types of metabolites produced in plants; primary metabolites and secondary metabolites. Primary metabolites are important for the plants regular metabolism such as growth and development. Secondary metabolites produced by plants may have little need for them. These are synthesized in almost all parts of the plant like bark, leaves, stem, root, flower, fruits, seeds, etc. During past several years, phytochemicals have been used worldwide as the traditional herbal medicine. Because of this, pharmaceutical industries as well as researchers put a greater emphasis on the phytochemical studies (Rice-Evans C., 2001). Also, these phytochemicals present in the different plant parts are used up by the local people for healing of certain disorders. These are also widely used in the field of agriculture. Secondary metabolites are economically important in the production of drugs, flavor and fragrances, dye and pigments, pesticides and food additives. Many of the drugs that are derived from the secondary metabolites are simple synthetic modifications or copies of these naturally obtained substances (Yogish and Raveesha, 2009).

1.2  Statements of Problem

During the past decades a lot of research has been carried out around antioxidants and their effects on health. There is a lack of a standard procedure to determine antioxidant activity in Nigeria. The antioxidant limitations and metabolism still pose a challenge to future research in this field, and researchers must try and overcome these drawbacks. The new trends in antioxidant treatments include compounds that behave like the enzyme in order to alleviate acute and chronic pain related to inflammation. Another promising research area are genetics, which aim to breed genetically modified plants that can  produce higher quantities of specific compounds, yielding higher quantities of antioxidants (Devasagayam et al., 2004; Suntres, 2011).