Antioxidant Properties of Cultivated Edible Mushroom, Agaricus bisporus, in Kenya.
Muna, Grace Adoyo
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Mushroomshave been widely used as food or food ingredients in many food products for a long time. Button mushrooms (Agaricus bisporus) grow widely in topic and subtropicalareas. Prevalence of oxidative cellular damage caused by reactive free radicals has raised interests from the global scientific and clinical community. Compelling epidemiological evidence exists for the link between consumption of antioxidantrich diet and a reduced risk of free radical-induced diseases. However, in the recent years, the restriction in the use of synthetic antioxidants, due to their toxicity and carcinogenicity, has caused an increased interest towards natural antioxidantsources. The general assumption is that edible cultivated mushrooms in Kenyaare rich in natural source of antioxidants. One such mushroom is the Agaricus bisporus that has been selected in this study. The main objective of the study was to evaluatethe antioxidant activity and levels of ethanoic and hot water extracts from Agaricus bisporus mycelium and fruiting body. The phytochemicals present in Agaricus bisporus ..were tested using standard procedures described by Krishnaiah et at (2009)and revealed that phenols, tannins, polyphenol, saponin, flavanoids, cardiac glycosides,terpenoids, reducing sugars; and alkanoids are present in all extracts. Phylobataninsterolsand anthoquinone were absent in MHWE. The total antioxidant activity was analysed using 1,l-diphenyl-z-picrylhydrazyl, hydroxyl, superoxide radicalscavenging and reducing power assays, along with total phenolic, ~-carotene lycopene,flavanoid and ascorbic acid concentrations in mycelium and fruiting body hot water and ethanoic extracts. Total phenolic, ~-carotene, lycopene, flavanoid and ascorbicacid composition of Agaricus bisporus extracts was analysed by calometric assaysdescribed by Barros et at (2008) with some modification and found to contain (40.26 04.61 mg/ml), (48.99 - 2.86 mg/g), (67.82 - 11.87 mg/g), (93.8 - 17.2 mg/g), and (11.62 - 10.22 mg/g), respectively. The mineral elemental analysis done using EDXRF (energy. dispenser x-ray fluorescence analytical method revealed that the samples contain zinc (42.9mg/l), iron (33-48.5 mg/l), copper (18-24 mg/l) and manganese(7.5-9 mg/l). The extracts showed more scavenging activity on hot water Hydroxyl radical and reducing power of ethanol extract. Generally the mycelium extractswere more effective raC\icalscavengers than the fruiting bodies. Due to the above characteristics, Agaricus bisporus mushroom could be considered a food complementwith antioxidative activity in the diet for the health benefits they present.