1.0 et al., 2013). An antioxidant is a molecule

1.0 INTRODUCTION

Reactive oxygen and
nitrogen species (ROS and RNS) are produced in cells by oxidative metabolic
reactions, enzymatic reactions and mitochondrial reactions. Such molecules are
also formed from tobacco, smoke, environmental pollutants, food constituents,
drugs, ethanol and radiation (Halliwell et
al., 2000). Free radicals and ROS are well known for their beneficial and harmful
effects (Valko et al., 2000). ROS at
low or moderate levels are beneficial to living system, such as in defensive
responses to infections and functions in cellular signaling pathways. However,
excessive free radical production in body leads to a condition known as
oxidative stress which produces harmful effects on human health, resulting in
oxidative damage of DNA, proteins, and lipids, activation of procarcinogens,
inhibition of cellular and antioxidant defense system, and change in gene
expression and contributing significantly to human diseases (Kumar et al., 2013).

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An antioxidant is a
molecule which stabilizes or deactivates free radicals before it attacks cells.
Antioxidants terminate the free radical chain reaction by donating electrons to
free radicals. The harmful effects of ROS and RNS are balanced by antioxidant
enzymes and by the action of non-enzymatic antioxidants (John et al., 2000). Intracellular Enzymatic
antioxidants include glutathione peroxidase, superoxide dismutase, and
catalase.Non-enzymatic antioxidants include flavonoids, ascorbic acid (vitamin
C), glutathione, carotnoids, alpha-tocopherol (vitamin E) etc. (Aruoma, 1998).

Non-enzymatic antioxidants
can be synthetic or natural, both are used in food and medicinal industry.
Butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA) are examples
of synthetic antioxidants. Although synthetic antioxidants are prominently used
in food industry for prevention of oxidation of food, but due to instability at
higher temperature and high volatility their effectiveness and safety is in
question (Kahl et al., 1993). Now
day’s preferences are given to natural antioxidants due to more health benefits
from natural sources as they can be easily included in diet.

Natural antioxidants fruits
and vegetables are rich in vitamins. Polyphenols are commonly found in plant
foods and are major natural antioxidants present in the diet. Use of natural antioxidants
in diet have possible role in prevention of various diseases linked with oxidative
stress including cancer, cardiovascular, and neurodegenerative diseases (Scalbert
et al., 2005).  However, all of the nutrients of food are not
absorbed by body. The bioavailability of fruits and vegetables differ because
of the interactions of chemicals and molecules within food matrix.

Antioxidants
have antimicrobial activity, infectious diseases are major threat especially to
developing countries, because of scarcity of medicine and emergence of
resistance microorganisms (Iwu et al., 2005).
Antimicrobials of plant origin are preferred over synthetic drugs, because of
possible side effects by synthetic drugs (Okeke et al., 2005).

 

In
this study we aim to investigate Tinospora
cordiofolia, Vallaris heynei
aqueous methanol (70% and 85%) leaf and stem extract for different properties
like total phenolic content (TPC), total flavonoid content (TFC), total
antioxidant capacity (TAC), ferrous chelating activities, free radical
scavenging activity, and antimicrobial activity. All these activities are
important contributors for evaluating the total antioxidant potential of the
plant extracts.

 

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