Antioxidant And Antimicrobial Activities Of Averrhoa carambola L. Fruits

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Department of Botany (Herbal Sciences), Birla College

An attractive fruit of Oxalidaceae, the carambola (Averrhoa carambola L.) also known as Golden Star had attained the status of a popular commercial crop in the United States. The unique star shaped and rich golden colour, in addition to its use as a fresh fruit and in jelly making, provide a considerable market potential as a garnish for salads and drinks. In western countries, the fruit is generally eaten at a ripe stage when it is yellow. However, in some Asian countries the green mature fruit is relished and consumed as fresh and in pickle preparation. In Ayurveda many medicinal uses of ripe fruits are also discussed.

The purpose of the present study was to evaluate Averrhoa carambola L. fruits as potential source of natural antioxidant and antimicrobial agents. Polyphenols and ascorbic acid content were determined as indicators for the presence of antioxidant compounds in fruits of Averrhoa carambola L. Antioxidant activities were determined by Ferric reducing antioxidant power and nitric oxide scavenging activity. Antimicrobial activity of different solvent extracts was also analysed against various Gram positive and Gram negative bacteria.

Nitric oxide radicals generated from sodium nitroprusside was found to be inhibited by Averrhoa carambola L. fruit extracts at various stages of ripening. However, the scavenging of nitric oxide by the extract was dependent on concentration and stages of ripening. The IC50 value for young, half ripe and ripe fruit was found to be 300, 250 and 250 ?g/ml respectively.
The reducing power of Averrhoa carambola L. fruit extracts increased with increasing amount of sample. Methanolic and water extracts of fruits showed antimicrobial activity against Escherichia coli, Salmonella typhi (Gram negative), staphylococcus aureus and Bacillus cereus (Gram positive).

Key words: - Averrhoa carambola L., antioxidant activity, antimicrobial activity