• Antioxidant and genoprotective activity of selected cucurbitaceae seed extracts and LC–ESIMS/MS identification of phenolic components

      Yasir, Muhammad; Sultana, Bushra; Nigam, Poonam S.; Owusu-Apenten, Richard K.; University of Agriculture, Faisalabad, Pakistan; University of California; Ulster University (Elsevier, 2015-11-30)
      Cucurbitaceae are one of most widely used plant species for human food but lesser known members have not been examined for bioactive components. The purpose of this study was to evaluate the antioxidant and genoprotective activities from three cucurbitaceae seeds extracts and to identify phenolic components by LC–ESIMS/MS analysis. From the results, the yield of seeds extract was 20–41% (w/w) and samples had 16–40% total phenols as gallic acid equivalents (GAE). Compared with methanol solvent, using acidified methanol led to increased extraction yield by 1.4 to 10-fold, higher phenolic content (149.5 ± 1.2 to 396.4 ± 1.9 mg GAE/g), higher DPPH radical quenching and enhanced enoprotective activity using the pBR322 plasmid assay. LC–ESI-MS/MS analysis led to identification of 14–17 components, based on authentic standards and comparison with literature reports, as mainly phenolic acids and esters, flavonol glycosides. This may be the first mass spectrometric profiling of polyphenol components from cucurbitaceae seeds.
    • A universally calibrated microplate ferric reducing antioxidant power (FRAP) assay for foods and applications to Manuka honey

      Bolanos de la Torre, Angelica A. S.; Henderson, Terence; Nigam, Poonam S.; Owusu-Apenten, Richard K.; ONIRIS, Ecole Nationale Vétérinaire; Ulster University; University of Chester; (Elsevier, 2014-11-07)
      The ferric reducing antioxidant power (FRAP) assay was recently adapted to a microplate format. However, microplate-based FRAP (mFRAP) assays are affected by sample volume and composition. This work describes a calibration process for mFRAP assays which yields data free of volume effects. From the results, the molar absorptivity (ε) for the mFRAP assay was 141,698 M−1 cm−1 for gallic acid, 49,328 M−1 cm−1 for ascorbic acid, and 21,606 M−1 cm−1 for ammonium ferrous sulphate. The significance of ε (M−1 cm−1) is discussed in relation to mFRAP assay sensitivity, minimum detectable concentration, and the dimensionless FRAP-value. Gallic acid showed 6.6 mol of Fe2+ equivalents compared to 2.3 mol of Fe+2 equivalents for ascorbic acid. Application of the mFRAP assay to Manuka honey samples (rated 5+, 10+, 15+, and 18+ Unique Manuka Factor; UMF) showed that FRAP values (0.54–0.76 mmol Fe2+ per 100 g honey) were strongly correlated with UMF ratings (R2 = 0.977) and total phenols content (R2 = 0.982)whilst the UMF rating was correlated with the total phenols (R2 = 0.999). In conclusion, mFRAP assay results were successfully standardised to yield data corresponding to 1-cm spectrophotometer which is useful for quality assurance purposes. The antioxidant capacity of Manuka honey was found to be directly related to the UMF rating.
    • A universally calibrated microplate ferric reducing antioxidant power (FRAP) assay for foods and applications to Manuka honey

      Bolanos de la Torre, Angelica A. S.; Henderson, Terence; Nigam, Poonam S.; Owusu-Apenten, Richard K.; Ulster University (Elsevier, 2014-11-07)
      The ferric reducing antioxidant power (FRAP) assay was recently adapted to a microplate format. However, microplate-based FRAP (mFRAP) assays are affected by sample volume and composition. This work describes a calibration process for mFRAP assays which yields data free of volume effects. From the results, the molar absorptivity (ε) for the mFRAP assay was 141,698 M−1 cm−1 for gallic acid, 49,328 M−1 cm−1 for ascorbic acid, and 21,606 M−1 cm−1 for ammonium ferrous sulphate. The significance of ε (M−1 cm−1) is discussed in relation to mFRAP assay sensitivity, minimum detectable concentration, and the dimensionless FRAP-value. Gallic acid showed 6.6 mol of Fe2+ equivalents compared to 2.3 mol of Fe+2 equivalents for ascorbic acid. Application of the mFRAP assay to Manuka honey samples (rated 5+, 10+, 15+, and 18+ Unique Manuka Factor; UMF) showed that FRAP values (0.54–0.76 mmol Fe2+ per 100 g honey) were strongly correlated with UMF ratings (R2 = 0.977) and total phenols content (R2 = 0.982)whilst the UMF rating was correlated with the total phenols (R2 = 0.999). In conclusion, mFRAP assay results were successfully standardised to yield data corresponding to 1-cm spectrophotometer which is useful for quality assurance purposes. The antioxidant capacity of Manuka honey was found to be directly related to the UMF rating