Radical scavenging and reducing properties of extracts of cashew shoots (Anacardium occidentale)
Introduction
Plants have been used for years as a source of traditional medicine to treat various diseases and conditions. Many of these medicinal plants are also excellent sources for phytochemicals, many of which contain potent antioxidant activities. The Malaysian population particularly the Malays is well-known for consuming traditional vegetables and herbs, raw or cooked as accompaniments with their main meal. These vegetables are consumed mainly for their aroma and taste as well as an appetite inducer. Many of these vegetables are claimed to possess medicinal properties although there are no scientific evidence to support this claim. One of the commonly consumed vegetables is the shoot of Anacardium occidentale. A. occidentale has been used to treat various ailments including malaria and yellow fever (Akinpelu, 2001) as well as diarrhea (Goncalves et al., 2005).
A. occidentale or cashew plant is a member of the family Anacardiaceae and is a tropical tree indigenous to Brazil. However, it is now widely grown in other tropical places particularly in India. The biological activities of this plant is widely reported and it has been shown to possess anti-viral (Goncalves et al., 2005), anti-fungal (Schmourlo, Mendonça-Filho, Alviano, & Costa, 2005), anti-bacterial (Akinpelu, 2001) and anti-inflammatory activities (Mota, Thomas, & Barbosa Filho, 1985). Another study reported the ability of extracts of A. occidentale to provide protection against streptozotocin-induced diabetes in rats (Kamtchouing et al., 1998). The shoot of this plant extract was also able to inhibit copper-induced LDL oxidation (Roach, Salleh, Runnie, Mohamed, & Abeywardena, 2003). More recently, the leaves of A. occidentale was reported to provide vasorelaxation effect when studied using isolated rat aorta (Runnie, Salleh, Mohamed, Head, & Abeywardena, 2004).
The antioxidant activities and phenolic content of this plant have been reported but mainly in the nuts and stem barks (Kornsteiner et al., 2006, Kubo et al., 2006, Trevisan et al., 2006) and not much information is available on the shoots which are also commonly consumed. Two recent studies have reported the antioxidant activities of the leaves of this plant (Abas et al., 2006, Runnie et al., 2004). In view of the limited data on the antioxidant activities and phenolic content of the shoots of A. occidentale, it was the aim of this study to attempt to provide further information on the phenolic content and antioxidant activities of this plant using several antioxidant assays. The assays consisted of estimating the ferric reducing capacity of the plant extracts and determining the scavenging effects of the plant extracts on the free radical DPPH· and ABTS·+, nitric oxide and superoxide anion. At the same time, the phenolic content of the plant was also estimated. As phenolic compounds are abundant in plants (Naczk & Shahidi, 2006), they may potentially be present in high concentrations in the shoots of A. occidentale and may act as potent antioxidants. Such information is valuable as plant extracts containing high antioxidant activities can prove beneficial for maintenance of optimal health. Furthermore, this may assist in providing evidence for the claimed medicinal properties of this plant.
Section snippets
Chemicals
All reagents and chemicals used in the experiments were of analytical grade and obtained mostly from Sigma. Solvents used for extraction of plants were purchased from Fisher Scientific. The polyphenolic standards, gallic acid, quercetin and rutin were obtained from Sigma. Water used was of Millipore quality.
Preparation and extraction of plant extracts
The shoots of A. occidentale were purchased from the local wet market and were processed on the day of purchased. The samples were washed, air dried and this was followed by complete drying
Total phenolic analysis
The Folin–Ciocalteau assay is a fast and simple method to rapidly determine the content of phenolics in samples. Phenolics or polyphenols are secondary plant metabolites that are ubiquitously present in plants and plant products. Many of the phenolics have been shown to contain high levels of antioxidant activities (Rice-Evans, Miller, & Paganga, 1996). This information has led to the determination of the total phenolic content of the sample understudy. Furthermore, several studies have
Conclusion
This study showed that among the methanol, hexane and ethyl acetate extracts of A. occidentale, the methanol extract possess significant antioxidant activities and their potency is in the order of methanol > ethyl acetate > hexane. Overall, the methanol extract of A. occidentale is the most potent in scavenging the DPPH and ABTS radicals, superoxide anion and nitric oxide as well as in reducing ferric ions whereas the hexane extract contained the weakest antioxidants. In addition, the antioxidant
Acknowledgements
This research project was supported by the fundamental grant (FP004/2003C) from University of Malaya, Kuala Lumpur, Malaysia.
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