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).
1.3
Aim and Objectives
Phytochemical screenining
and in-vitro antioxidant activity of leaf extract of Pterocarpus soyauxii (ORA) and Pterocarpus santalinoides
(UTURUKPA)
The objectives of this study are
1. Quantitative and Qualitative ( phytochemical) analysis
on pterocarpus soyanxii (ora) and pterocarpus santalinoides (uturukpa).
2. To
estimate flavonoids and flavonoils content on pterocarpus soyanxii (ora) and pterocarpus
santalinoides (uturukpa).
3. To
determine reducing power on pterocarpus
soyanxii (ora) and pterocarpus
santalinoides (uturukpa).
4. To
determine hydrogen peroxide scavenging activity on pterocarpus soyanxii (ora) and pterocarpus
santalinoides (uturukpa).
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