Evaluation of Antioxidant Activity of the Acetylated and Hydrolysed Derivatives of Vanillin

Evaluation of Antioxidant Activity of the Acetylated and Hydrolysed Derivatives of Vanillin

CHAPTER ONE

INTRODUCTION AND REVIEW OF RELATED LITERATURE

1.1 General Introduction

Vanillin is a pleasant-smelling aromatic compound occurring naturally in Vanilla beans. It is a phenolic aldehyde and is also found in roasted coffee, Chinese red pine and leptotes bicolour. In the search for novel pharmacologically active compounds, derivatives of vanillin are promising compounds with high potentials for development into drugs. Many derivatives of vanillin are better antioxidants with several health benefits due to their strong free radical scavenging properties. It is also well-known that vanillin has antimicrobial activity. Various studies have revealed the importance of antioxidants in the general well-being of the body.

Oxidative stress, the imbalance between reactive oxygen and nitrogen species production and the antioxidant defence plays a vital role in different pathophysiological conditions, example cardiovascular diseases, cancers and neurodegenerative disorders. In the above diseases, reactive oxygen species (ROS) such as superoxide onion, hydrogen peroxide and hydroxyl radical attack proteins, lipids as well as DNA and cause genetic instability, angiogenesis, chemo-resistance, proliferation and invasion. Recently, several vanillin-based dendrimers with enhanced antioxidant properties have been synthesized. These dendrimers have been found to have protective effects on fatty acid, DNA and lipoprotein, thereby preventing several diseases and enhancing survival.

 1.2  Statement of Research Problems

Dietary and endogenous antioxidants are essential for the elimination of free radicals in the body. Thus, preventing diseases associated with oxidative stress. Several antioxidant currently available exhibit some level of toxicity and are quite expensive. Consequently, there is a high demand for novel pharmacologically active antioxidants with higher potency, low toxicity and less cost. Hence, the need for evaluating the antioxidant activity of the acetyl and hydrolysed derivatives of vanillin.

 1.3  Justification of the Study

Free radicals in the body alter molecules, generating a condition known as oxidative stress. Oxidative stress has been linked to various human diseases such as atherosclerosis, cancers, stroke as well as Parkinson’s and Alzheimer’s diseases. This results when the free radicals in the body outnumber the antioxidants essential for proper physiological function. The supplementation of antioxidants from external sources can assist in controlling oxidative stress. This justifies the search for effective and non-toxic compounds with antioxidant activity from vanillin.

 1.4   Aim of the Study

To evaluate the antioxidant activity of the acetylated and hydrolysed derivatives of vanillin.

1.5   Objectives of the Study

1. To carry out some monographic determinations of vanillin such as, melting point
2. To determine its optical point
3. To determine its refractive index
4. To synthesize the acetylated and hydrolysed derivatives
5. To evaluate the antioxidant activity of the vanillin as well as that of its derivatives
6. To determine the refractive index of the derivatives
7. To determine the optical rotation of the derivatives
8. To obtain the IR and GC/MS spectral characteristics of the vanillin and that of its derivatives.

 1.6   Physical Attributes and Constants of Vanillin

• Appearance –           Crystalline
• Colour –           White
• Taste –           Pleasant (Vanilla)
• Odour –           Pleasant
• Boiling Point –           285⁰C
• Melting Point –           81⁰C
• Acidity (PKa) –           781
• Basicity (PKb) –           216
• Molar Mass –           15g/mol
• Density –           056g/cm³
• Vapour Pressure –           2 x 10^-3mmHg

 1.7       Review of Related Literature

Antioxidants are compounds that inhibit oxidation; a chemical reaction that produces free radicals and chain reactions that may damage the cells of living organisms. They donate electrons to free radicals without becoming free radicals themselves. Free radicals are highly reactive, unstable molecules which the body produces in reaction to food and the environment. Antioxidants are also known as free-radical scavengers because they scavenge or neutralise free radicals. Regular consumption of anti-oxidative vegetables and fruits has been found to minimize the risk of oxidative damage.

 (a)        Types of Antioxidants

The various antioxidants found to exist include natural antioxidants, synthetic antioxidants, dietary antioxidants, endogenous antioxidants and exogenous antioxidants.

(b)       Natural Antioxidants

Natural antioxidants are synthesized in the human body through sources. They are constituents of many fruits and vegetables. Common natural antioxidants include Vitamin C
(Ascorbic acid), Vitamin E (Tocopherol), Vitamin A (Carotenoids), various polyphenols including flavonoids, anthocyanin (a type of flavonoid), lycopene (a type of carotenoid) and coenzyme Q (Ubiquitin).

(c)        Synthetic Antioxidants

            Synthetic antioxidants are chemically synthesized since they do not occur naturally and are added to food as preservatives to help prevent lipid oxidation. Examples are: butylated hydroxyl toluene (BHT), Butylated hydroxyl anisole (BHA), Tert-butyl hydroquinone (TBHQ) and propyl gallate (PG).

(d)       Dietary Antioxidants

Various antioxidants are derived from food example includes, tocopherols, ascorbates, carotenoids and oxy carotenoids such as lycopene and lutein. Vitamin C is considered the most important water-soluble antioxidant. It performs its action in the extracellular fluid compartment and is capable of neutralizing reactive oxygen species in the aqueous phase before lipid peroxidation is initiated. Vitamin E, a major lipid-soluble antioxidant is the most affective chain-breaking antioxidant within the cell membrane, where it protects the membrane’s fatty acids from lipid peroxidation. Vitamin C is capable of regenerating Vitamin E. βeta carotene and other carotenoids are also believed to provide anti-oxidant protection to lipid-rich tissues. Research suggests that beta carotene may work synergistically with Vitamins in anti-allergenic, anti-viral, anti-inflammatory and anti-aging effects.

(e)        Endogenous Antioxidants

The body generates its own antioxidants known as endogenous antioxidants. These antioxidants are products of the body’s metabolism. They may be enzymatic or non-enzymatic. Examples are superoxide dismutase, catalyse and glutathione.

(f)        Exogenous Antioxidants

Exogenous antioxidants can be derived from natural sources (Vitamins, flavonoids, anthocyanin, some mineral compounds) but can also be synthetic compounds like BHT, BHA and gallates.