ANTIOXIDANT ACTIVITIES OF ESSENTIAL OIL

VIETNAM NATIONAL UNIVERSITY, HANOI VNU UNIVERSITY OF SCIENCE FACULITY OF CHEMISTRY Topic ANTIOXIDANT ACTIVITIES OF ESSENTIAL OIL Supervisor Dr Nguyen Hoang Yen Performed of students Tran Thi Thuy Van Hanoi – 2021 ACKNOWLEDGEMENT First of all, I would like to express my gratitude and sincere thanks to Dr Nguyen Hoang Yen were helpful, oriented way of thinking and way of doing science for children Those are very valuable suggestions not only in the process of making this thesis but also a step.

VIETNAM NATIONAL UNIVERSITY, HANOI

VNU UNIVERSITY OF SCIENCE

FACULITY OF CHEMISTRY

***

Topic:

ANTIOXIDANT ACTIVITIES OF ESSENTIAL OIL

Supervisor: Dr Nguyen Hoang Yen

Performed of students: Tran Thi Thuy Van

Hanoi – 2021

ACKNOWLEDGEMENT

First of all, I would like to express my gratitude and sincere thanks to

Dr Nguyen Hoang Yen were helpful, oriented way of thinking and way of doing science for children Those are very valuable suggestions not only in the process of making this thesis but also a stepping stone for me in the process of studying and setting up a career in the future

And finally, thank you to family and friends who are always willing to share and help in study and life Hopefully, we will stick together forever

Wish the best will always accompany everyone

Hanoi, May 20, 2021

Student

Tran Thi Thuy Van

CONTENT

ACKNOWLEDGEMENT 2

CONTENT 3

LIST OF ABBREVIATIONS 4

LIST OF FIGURES 5

LIST OF TABLES 5

INTRODUCTION 6

CHAPTER 1: OVERVIEW 7

1.Essential oils and their antioxidant activity 7

1.1 Overview of essential oils 7

1.2 Antioxidants 11

1.3 Antioxidant activity of essential oils 15

1.4 Plants rich in antioxidants 18

2 Methods used for analysis 19

2.1 Determination of antioxidant activity by DPPH method 19

2.2 Test methods inhibitory activity radical NO[12] 20

2.3 TBARS method 21

3 Study on extracting and evaluating antioxidant effects of garlic essential oil from garlic bulbs (Allium sativum L.) [16] 21

3.1 Brief about garlic 21

3.2 Resources 22

3.3 Device 22

3.4 Research Methods 22

CHAPTER 2: FURUTE RESEARCH DIRECTIONS 25

REFERENCES 26

LIST OF FIGURES

Scheme 1 Simplified Mechanism of Hydrocarbon Autoxidation and

Antioxidant Protection………12 Scheme 2 Some Common Phenolic EO Components……… 18 Scheme 3: Effect of antioxidant concentration on initial reaction rate with DPPH……… ………….21

LIST OF TABLES

Table 1: Some foods rich in antioxidant………20

INTRODUCTION

Plant essential oils are used for many different purposes such as flavoring foods, additives in cosmetics , etc In particular, essential oils have very good antioxidant properties that can replace antioxidants synthetic oxidation

Realizing the great application of the antioxidant activity of essential oils and to familiarize and improve knowledge and skills, I have chosen this topic for my thesis

CHAPTER 1: OVERVIEW 1.Essential oils and their antioxidant activity

1.1 Overview of essential oils

1.1.1 What is essential oils?

Essential oils is a form of liquid containing aromatic compounds

volatile extracted from the leaves; trunk; flower; roots; or other plant parts There are many methods to extract essential oils such as steam distillation, solvent extraction method, pressing method, etc

Essential oils are likened to the resin of a tree, so they bring the vitality and purest energy of herbs from nature and are 50-100 times stronger than dried herbs (herbs) Most essential oils are clear, with the exception of a few essential oils like patchouli, orange oil , and lemongrass , which are yellow or amber in color

Essential oils are used in the production of perfumes, cosmetics,

shower gels, soaps, flavoring drinks and foods, or adding scents to

incense/agarwood and other household cleaning products In particular,

essential oils have been and are one of the most important ingredients in cosmetic products such as perfumes and lotions About 3000 essential oils have been discovered and nearly 300 are commercially produced such as jasmine, rose, lavender, etc Essential oils are also used as a therapeutic agent for various problems digestive problems, muscle pain, insomnia In

addition, the antioxidant activity of essential oils has also been paid special attention by researchers [2, 3]

Essential oils have also historically been used in the field of medicine Medicinal applications range from skin beautification to cancer treatment and are often purely based on historical accounts of the use of essential oils for these purposes Claims about the effectiveness of essential oil medical

treatments, in particular as a cancer treatment, are currently subject to

regulatory regulations in many countries

1.1.2 Classification of essential oils

There are two types of essential oils: Pure Essential Oils and

Non-pure Essential Oils

Pure essential oils are essential oils that have not been mixed with other chemical components, which are very good and safe for health

Non-pure essential oils are essential oils that are mixed from pure essential oils with other chemicals but still retain the aroma of the essential oil

1.1.3.Structure of the components in the essential oil

They can be divided into four main groups [2] :

• Compounds containing nitrogen (N) and sulfur (S)

Isothiocyanate derivatives, Alicin

For example:

Methylalranilat

1.1.4.Physical properties of essential oils

At room temperature, most essential oils are liquid Usually colorless or pale yellow, the longer it is left over due to oxidation, the color may darken Essential oils have a pleasant aroma , some are pungent

Essential oils are volatile at room temperature, have a density less than

1 Insoluble in water, soluble in organic solvents and alcohols The boiling point depends on the composition, so fractional distillation can be used to separate each component in the essential oil

The refractive index of essential oils is from 1,450 to 1,560 [2]

1.1.5 Chemical composition of essential oils

Essential oils are usually extracted by steam distillation from leaves, stems, flowers, bark, roots or other plant components The hydrocarbons commonly found in essential oils are terpenes (C10H16 )n open-chain or cyclic Any essential oil has the following ingredients [ 5-10 ] :

• Monoterpenes: Found in almost all essential oils, Monoterpenes have the molecular formula C10 H16 open-chain Effective in disinfecting and

as a tonic in nature They also have the ability to filter the air, making leaves protect cells, such as miaxene and oximene found in bay flower essential oil

• Sesquiterpenes: Although not as volatile as monoterpenes, linear and cyclic sesquiterpenes, notably Farnesene These substances have about

15 carbon atoms They have soothing, infective, and

anti-inflammatory effects

• Phenol: most of the essential oils are antiseptic, stimulating the body when used in small doses When used in high doses, it is a poison to the nervous system and causes skin irritation Some phenols such as

• Esters: The esters evaporate quickly and give flavor to the fragrance Some esters are present in essential oils: ethyl anthranilate, benzyl acetate, In addition to the use of aromatherapy for essential oils, these esters have antispasmodic, antibacterial and anti-inflammatory effects, especially non-irritating skin

• Aldehytes: There are many aldehydes in essential oils, but now all aldehydes are obtained through chemical synthesis Only aldehydes such as Cuminic Aldehydes, Citral and Citronellal are extracted

directly from natural materials Aldehytes have anti-inflammatory effects, with properties similar to ketones and alcohols However, high amounts of aldehydes can cause severe skin irritation and mucous membrane formation

• Other compounds: In addition to the compounds mentioned above, essential oils also contain oxide group compounds such as: amino acids (antranilic acid), lactones (coumarin, ambretolite), compounds

containing sulfur such as: (anlylisosulfocyannat), nitrogenous

compounds (methyl antranilate)

1.1.6 The role of essential oils for plants

In nature, essential oils are widely distributed in flora, especially

concentrated in a few families: Asteraceae, Orange family, Ginger family, etc

In plants, essential oils are found in all parts: leaves , flowers, fruits, bark, roots, stems, [2]

Essential oils that exist in plants play a significant role in the

development of the plant According to many previous studies for can be seen , essential oils in the plant have a direct role listed as follows:

• Protect plants from the effects of diseases, pathogens, harmful bacteria

• Covers wood wounds to help prevent the attack of harmful bacteria

• Prevent fungal diseases

• Promote metabolism, transport water and mineral salts for plants

• Increases the efficiency of biochemical reactions in plants such as

enzymatic reactions

1.2 Antioxidants

1.2.1 Define

An antioxidant is a chemical that helps prevent or slow down the

oxidation of other substances Oxidation is a type of chemical reaction in which electrons are transferred to an oxidizing agent, capable of generating free radicals, causing a chain reaction that destroys living cells Antioxidants prevent this damage by removing free radicals, inhibiting oxidation by

oxidizing themselves To do so, reducing agents (such as thiols or

polyphenols) are often used as antioxidants [11]

1.2.2 Mechanism

Focusing on relevant processes in biological systems or in food science, the most common materials to be protected are lipids, proteins, carbohydrates and to a small extent other organic molecules make up animal or plant

tissues Their oxidation occurs by a radical chain reaction mediated by

peroxyl radicals (ROO •) in parallel with hydrocarbon autooxidation

The process, outlined in scheme 1,

produce ROOH hydroperoxide (substrate oxidized substance) and another radical The chain reaction takes place for many cycles before two random radicals quench each other in one step, called termination The number of cycles occurring between the start and end is named "string length"

Compounds capable of degrading this radical chain reaction are known

as direct antioxidants and are divided into two main groups depending on their interfering mechanism Preventive antioxidants interfere with initiation; that is, they slow down the initial formation of radicals Examples of them are catalase enzymes and metal chelators such as phytic acid (By preventing redox-active metal ions (eg, Fe 2 + ) in their oxidized form (eg, Fe 3 + ), metal chelators can prevent the occurrence of chemical type of Fenton, which

is one of the most important radical-initiating processes.) slows down (or prevents) auto-oxidation by competing with propagation reactions; that is, they react with peroxyl radicals more rapidly than easily oxidized substrates

to form species that do not propagate the oxidation chain Because preventive antioxidants are completely inactive once the process begins, chain-breaking antioxidants are by far the most important direct antioxidant

The fact that a compound can react with several radicals does not mean

it is an antioxidant, unless it is a peroxyl radical; reacts much faster than the radical reaction with the material to be protected, for example, unsaturated lipids; and the products of the reaction are species that are not capable of propagating a chain reaction Phenol is an antioxidant that breaks the

prototype chain

Some compounds that are not supplied to related antioxidant systems or food products, still increase antioxidant defenses in living systems, for

example, by inducing expression or enhance the activity of antioxidant

enzymes These compounds are referred to as indirect antioxidants with

related examples among natural products [12]

1.2.3 Types of antioxidants in foods

1.2.3.1 Natural antioxidants

Substances unsaturated fatty in biological tissues are relatively stable The reason is because biological tissues contain antioxidants as well as

enzymes that prevent oxidation

• Ascorbic Acid (Vitamin C):

Vitamin C or ascorbic acid is a major nutrient for higher animals and other species The presence of ascorbate is important for the metabolic

reactions of animals, plants and the internal functioning of human organs It is known as vitamin whose deficiency is the cause of scurvy (due to lack of vitamin C in daily life)

Vitamin C has antioxidant activity when it reduces oxidizing chemicals such as hydrogen peroxide In addition, it will also reduce metal ions that generate free radicals through Fenton reactions

2Fe3+ + ascorbate → 2Fe2 + + Dehidroascorbate

2Fe2 + + 2H2O2 → 2Fe3 + + 2OH

-• Tocopherol (Vitamin E) :

Vitamin E is the collective name for a set of eight related tocopherols and is a fat-soluble vitamin with antioxidant properties Among them, the α-tocopherol form is the most important fat-soluble antioxidant, which has the ability to protect cell membranes from oxidation by reacting with lipid

radicals produced in the reaction transmission line Thereby eliminating intermediate free radicals and preventing continuous propagation reactions Vitamin E is separated during the oil refining process Vitamin E is abundant

in soybean oil, cereals

• Carctenoids: also exhibit antioxidant activity

Among them, carotene showed the strongest antioxidant activity

Flavanone and flavonol: are substances with high antioxidant activity that can be found in plants such as green tea leaves, herbs, wood

• Vanillin: external role flavor, it also acts as a chemical ng oxidation good In addition, the reactions formed in the Maillard reaction are also

antioxidants that form in foods

1.2.3.2 Synthetic antioxidants

Antioxidants in total foods must satisfy the following requirements: Non-toxic, have high oxidizing activity at low concentrations, can be

concentrated on the surface of the oil phase, stable under the technical

conditions of the process food processing

Commonly used synthetic oxidizing agents are:

BTH (Butylated hydroxyltoluene), BHA (Butylate hydroxyanisole), synthetic tocopherol, TBHQ (Tertbutyl hydroquinone), dodecyl gallate,

propyl gallate, ascorbyl palmitate…

• BHT (Butylated Hydroxytoluene)

BHT is also known as bis(1,1-dimethylethyl)-4-methylphenol; di-tert-butyl-p-cresol; 2,6-di-tert-butyl-4-methylpheno BHT is formed by the reaction of para-cresol (4-methylphenol) with isobutylene (2-methylpropene) catalyzed by sulfuric acid, with the molecular formula C15H24O

2,6-This substance acts similarly to a synthetic vitamin E, primarily acting

as an inhibitor of oxidation, an unsaturated process in which (usually) organic compounds are attacked by oxygen in the atmosphere The antioxidant BHT

catalyzes the reaction by converting the peroxide free radicals in the bound hydroperoxides This affects the antioxidant function by donating a hydrogen atom:

RO2 + ArOH → ROOH + ArO

• BHA (Butylated Hydroxyanisole)

BHA is a mixture of 3-Tetiary-butyl-4-hydroxyanisole or 3-and

2-tertiary-buty-4-hydroxyanisole, also known as BOA In which, the first

isomer is more dominant (>= 90%) Has the molecular formula C11H16O2

The mechanism of action is similar to that of BHT, which prevents the chain reaction of fat oxidation BHT works by electron donor mechanism to control the free R radical

BHA is absorbed through the small intestine wall, participates in

metabolism, is suspected to cause allergies or cancer Due to exist in cell tissues and participate in a number of metabolic processes It is an effective antioxidant for animal fats and baked goods, stabilizes the end product, and is commonly used in shortening, vegetable oils, potato products, soups, chewing gum, cereals, which are most widely used in high-fat products, do not work with unsaturated vegetable oils Often used in combination with other

antioxidants

1.3 Antioxidant activity of essential oils

Essential oils have been used for millennia for their health benefits, well documented in ancient documents Several health-promoting properties,