Preventing ultraviolet light-induced damage: the benefits of antioxidants

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Abstract
Extracts of fruit peels contain antioxidants that protect the bacterium Escherichia coli against damage induced by ultraviolet light. Antioxidants neutralise free radicals, thus preventing oxidative damage to cells and deoxyribonucleic acid. A high survival rate of UV-exposed cells was observed when grapefruit or grape peel extract was added, compared to UV-exposed cells without extract. This laboratory activity can be used to introduce the scientific method to GCSE or Alevel biology students and equivalent, in which they formulate the hypothesis, identify the controlled, independent and dependent variables and design control set-ups. Students are also exposed to microbiological techniques such as the maintenance of aseptic conditions, serial dilution and plating of bacteria. Safety issues and proper disposal of bacterial cultures are also highlighted. Statistical analysis using the t-test revealed that differences in the mean number of colonies from UV-treated and non-UV-treated cultures in the controls were statistically significant at α=0.05, suggesting that UV was lethal to E. coli. However, when fruit peel extracts were added, differences in the mean number of colonies were statistically insignificant, indicating that cells survived the UV treatment when antioxidants were present. Recycling fruit peels to obtain medically important substances is a potential application of this investigation.