Antioxidant properties of several tropical fruits: A comparative study

Abstract

Nine tropical fruits were analyzed for total phenol contents, ascorbic acid contents and antioxidant activities. The antioxidant activities were evaluated based on the ability of the fruit extracts to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH), reduce iron(III) to iron(II) and to bind to iron(II) ions. The results were compared to those of orange. It was found that guava, papaya and star fruit have higher primary antioxidant potential, as measured by scavenging DPPH and iron(III) reducing assays. Banana, star fruit, water apple, langsat and papaya have higher secondary antioxidant potential as measured by the iron(II) chelating experiment.

Introduction

Fruits are rich with antioxidants that help in lowering incidence of degenerative diseases such as cancer, arthritis, arteriosclerosis, heart disease, inflammation, brain dysfunction and acceleration of the ageing process (Feskanich et al., 2000, Gordon, 1996, Halliwell, 1996). Antioxidants are substances that can prevent or delay oxidative damage of lipids, proteins and nucleic acids by reactive oxygen species, which include reactive free radicals such as superoxide, hydroxyl, peroxyl, alkoxyl and non- radicals such as hydrogen peroxide, hypochlorous, etc. They scavenge radicals by inhibiting initiation and breaking chain propagation or suppressing formation of free radicals by binding to the metal ions, reducing hydrogen peroxide, and quenching superoxide and singlet oxygen (Shi, Noguchi, & Niki, 2001). The most abundant antioxidants in fruits are polyphenols and Vitamin C, Vitamins A, B and E and carotenoids are present to a lesser extent in some fruits. These polyphenols, most of which are flavonoids, are present mainly in ester and glycoside forms (Fleuriet & Macheix, 2003).

Malaysia is a tropical country with a large diversity of fruits. The antioxidant properties of a number of tropical fruits have been investigated (Jimenez-Escrig et al., 2001, Leong and Shui, 2002, Someya et al., 2002) on an individual basis using different analytical methods. It is therefore difficult to rank the antioxidant capabilities of these tropical fruits based on the existing literature reports, although study to compare the antioxidant capabilities has been reported for temperate fruits (Garcia-Alonso, Pascual-Teresa, Santos-Buelga, & Rivas-Gonzalo, 2004). It is the aim of this paper to measure the antioxidant properties of some common fruits available in tropical regions by using three common standard methods: 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging assay, ferric reducing assay using ferricyanide ion and ferrous ion chelating assay. Each of the above assays measures different aspects of the antioxidant activity of the fruit extracts.