Table of Content

Introduction…………………………………………………………………………………………………………….2

Structure, Properties and Biological Activities of Antioxidant………………………………….3

Caffeine…………………………………………………………………………………………………………..3

Chlorogenic acid…………………………………………………………………………………………..…4

Caffeic acid……………………………………………………………………………………………………..4

Antioxidant and Human Disease……………………………………………………………………………..5

Antioxidant and Cancer…………………………………………………………………………………..6

Liver Cancer…………………………………………………………………………………………………….7

Colon Cancer…………………………………………………………………………………………………..8

Breast Cancer………………………………………………………………………………………………….9

Prostate Cancer………………………………………………………………………………………………10

Antioxidants and Type 2 Diabetes Mellitus……………………………………………………..11

Limitations and Further Research Direction……………………………………………………………13

Conclusion………………………………………………………………………………………………………………14

Reference……………………………………………………………………………………………………………….14

Antioxidants in Coffee and Their Potential Health Benefits

1. Introduction

Coffee is a popular drink worldwide, in Australia; it is the second highest type of beverage consumed after water (Australian Bureau of Statistics, 2014). Although coffee consumption has showed some negative health effects, such as increased risk of spontaneous abortion in pregnant women, habitual coffee intake is associated with a range of health benefits due to its rich antioxidant profile (Preedy, 2014). It was found that coffee has more antioxidant activity than green tea, black tea and red wine (Bowden, 2007). Furthermore, coffee ranked eleventh in terms of the antioxidant content of different food by serving size, after several types of berries (Pérez-Jiménez et al., 2010). While eating several servings of berries are rare, drinking a few cups of coffee a day is more common, therefore, coffee is known as the biggest source of dietary antioxidant (Perez-Jimenez et al., 2011; Zujko et al., 2012).

Antioxidants are broadly divided into exogenous and endogenous. While human body is capable of producing antioxidant, it is usually insufficient, thus dietary source of antioxidant is also vital (Zampelas and Micha, 2015). Antioxidants are molecules that inhibit oxidation, which is process characterized as the loss of electrons. Free radicals are produced in oxidation. These free radicals can further initiate chain reaction of oxidizing other molecules, causing cell damage or even cell death (Bagchi, Moriyama and Swaroop, 2016). Nevertheless, antioxidants are capable to protect the body from the detrimental effects brought by free radicals. Caffeine, caffeic acid, chlorogenic acid and hydroxyhydroquinone are antioxidants that can be found in coffee (Butt and Sultan, 2011).

Numerous findings indicate that antioxidants present in coffee play a role in delaying or preventing type 2 diabetes and degenerative conditions, including several types of cancer (Bagchi, Moriyama and Swaroop, 2016; Hoelzl et al., 2010). As a result, it is essential to understand the mechanism and action of antioxidant in preventing the development of chronic disease. This knowledge is vital given that coffee is a highly consumed beverage in Australia. The health authority can educates the general public and raises their awareness regarding the health promoting property of their beloved beverage. For maintaining good health, prevention is better than medical treatment in terms of cost and effectiveness. This review summarises the present understanding of the biological effects of exogenous antioxidant and their role in human health and disease from a range of epidemiological, in vitro and in vivo studies. In particular, colon, liver, breast and prostate cancers and type 2 diabetes mellitus are discussed due to their contribution to mortality of Australians and increasing prevalence in Australia.

1. Structure, Properties and Biological Activities of Antioxidant

Coffee contains a range of antioxidants that contributes to its health benefit. As mentioned in the introduction, antioxidants are able to protect the body by inhibiting oxidation. In human, normal metabolism generates free radicals as by-products. Damage caused by free radicals can be serious when the generation of free radicals increases, as it can leads to the development of various pathological and chronic conditions (Herrera et al., 2009). However, antioxidants can mitigate the damage brought by free radicals. Huang, Ou, and Prior (2005) defined dietary antioxidants as “substances which can sacrificially scavenge reactive oxygen/nitrogen species to stop radical chain reactions, or can inhibit the reactive oxidants from being formed in the first place”. In addition to this definition, antioxidants can neutralize free radicals or terminate the chain reaction by being oxidized themselves (Bagchi, Moriyama & Swaroop, 2016).

While cancer, heart disease, diabetes and premature ageing are linked to inadequate antioxidant levels or function in the body, the properties and actions of antioxidants are worth investigating (Siti, Kamisah and Kamsiah, 2015). The main antioxidants found in coffee are described while their chemical structures, concentration in coffee and other biological activities are illustrated in Table 1.

Caffeine

Caffeine, also known as 1,3,7-trimethylxanthine, is a purine alkaloid and a natural occurring substance found in various plants. Coffee is a main source of caffeine where 50% of caffeine intake for Australians comes from coffee (Australian Beverage, 2013). During the coffee bean roasting process, caffeine is not significantly altered in terms of its chemical structure and the amount of caffeine in beans are not remarkably reduces, yet a small amount can be lost due to sublimation (Chu, 2012). Additionally, in the human body, caffeine is rapidly and almost fully digested and absorbed in the stomach and small intestine and then distributed to tissues, including the brain (Ludwig et al., 2014). Liver is the major site of caffeine metabolism where a serious of demethylation occurs. After absorption, caffeine exhibits its physiological function via the antagonism of the A1 and A2 subtypes of the adenosine receptor located in the brain (Frost-Meyer & Logomarsino, 2012). Nevertheless, high level of caffeine is circulating around the body after coffee consumption with a maximum concentrati