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1.0: Introduction
Our skin is constantly exposed to air, pollutants, UV rays, and any other chemical and mechanical factors that can promote the production of free radicals and reactive oxygen species (ROS). An overproduction and accumulation of ROS may bring into disproportion in oxidative stress. Oxidative stress is an imbalance between free radicals and antioxidants in the body. Oxidative damage to macromolecules increases with age and has been assumed as an inner damage resulting to aging, degenerative diseases, atherosclerosis, brain dysfunction, inflammatory diseases, cardiovascular diseases, and cancer.
There are 3 types of ultraviolet radiation classified to their own wavelengths which are UVA, UVB and UVC. However only UVA and UVB rays reach the earth’s surface causing skin cancer and skin photoaging while UVC rays do not reach the earth’s surface as they are absorbed by ozone layer. The epidermis layer of the skin (the outer layer) can be penetrated by UVB resulting to overproduction of ROS which eventually causes skin aging.
Skin aging can be divided into two classes which are extrinsic and intrinsic aging. Intrinsic aging is gene dependent and will occur over time while extrinsic aging is mainly caused by environmental aspects, mainly ultraviolet radiation, which is called photoaging and is identified by wrinkles and dryness.
Skin aging can be prevented with antioxidant rich products and one of the famous antioxidant in skincare line is ascorbic acid (vitamin C). Apart from ascorbic acid, polyphenols are also known to combat skin photoaging, such as Gallic Acid. Due to its molecular weight, Gallic Acid out of many polyphenols has been proposed to have strong antioxidant activities in many studies. Gallic Acid (3,4,5 – trihydroxylbenzoic acid) is made up of 3 hydroxyl groups and one carboxyl group and can be widely found in leafy vegetables, fruits, nuts, witch hazel, etc and can also be obtained from hydrolysis of Tannins in green tea leaves and oak barks. The 3 hydroxyl groups are bonded in an ortho position and this arrangement is the determining factor for the strong antioxidant property of phenolic compounds.

1.1: Problem Statement:
In previous studies, there are not much of proofs that Gallic Acid alone can possess a great antioxidant in combating skin photoaging but many studies have focused on dermatological and application in cosmetics and medicines. Therefore, derivatives of Gallic Acid are synthesised to make it stable and won’t cause any bad reaction to the human skin. There are many Gallic Acid derivatives used in industrial uses such as Propyl Gallate, Octyl Gallate, Lauryl Gallate, Methyl Gallate, Phenyl Gallate etc. Gallic Acid derivatives have been synthesised to have anticancer, anti-inflammatory and antioxidant properties, scavenging free radicals by getting involved the signal pathways of calcium (II) ions and oxygen free radicals. Galato et al have demonstrated by studying 8 phenolic ; analogous compounds, that the antioxidant activity of a molecule increases with the higher number of hydroxyl group attached to the aromatic ring.
According to Boehm and Williams (1943), the antioxidant activity of Gallic Acid derivative which is Propyl Gallate came from hydrogen-donating hydroxyl group in which it will be stable in neutral or mild acidic solutions but will be unstable in slightly alkaline environments. Although, Propyl Gallate is widely known as a food additive due to its antioxidant properties, it is also can be used in cosmetics.
Therefore, this study aims to compare Gallic Acid and its derivatives and synthesize Propyl Gallate from Gallic Acid. The ability of Propyl Gallate to scavenge free radical leads to enzyme inhibition, inhibition of biosynthetic process and neuromuscular response to chemicals, protection from ultraviolet radiation, chemoprotection, antimutagenesis, antiteratogenesis, anticariogenesis, anticarcinogenesis and antitumorigenesis. There is a phototoxicity study in 1977 where ears of guinea pigs are tested using a sun protection stick containing 0.003% of Propyl Gallate and no irritation was seen on the tested guinea pigs.

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1.3: Objectives
• To synthesize and characterize Propyl Gallate from Gallic Acid by esterification method
• To evaluate the antioxidant effect of Gallic Acid and its derivatives in cosmetics
• To study the effects of Gallic acid and its derivatives in relation to UVB-induced skin photo aging

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