RESUMEN
The effect of antioxidants, temperature, packaging materials and storage periods was investigated in medium shelled walnut kernels (Hamdan) variety. The kernels were mechanically dried (40 °C), standardized and treated with butylated hydroxylanisole and butylated hydroxytoluene in combination at concentrations (0.015%) each. Then packed in laminates under vacuum and high density polyethylene non vacuum packaging materials and stored under ambient and refrigerated temperature conditions (4 °C) for a period of 9 months. All tested extracts possessed appreciable antioxidant potential. The bioactive compounds were identified by using chromatographic techniques (GC-MS and LC-MS). Before storage dried kernels exhibited high values of total phenols (31.23 mgGAE/gm), DPPH (215.13 µmol TAEg-1) and low value of non enzymatic browning (0.63 OD). Walnuts packed in laminates under vacuum and refrigerated conditions exhibited higher values of total phenols, total flavonoids, DPPH and subsequently lower change in non-enzymatic browning reactions throughout the experiment. After 90 days of storage maximum loss in total phenols and DPPH value and highest value of non enzymatic browning was observed in high density polyethylene non vacuum packaging materials under ambient temperature. The major phenolic components identified by GC/MS and LC/MS analysis were linoleic acid, oleic acid, hexadecanoic acid, epicatechin, quercetin, epicatechin and ellagic acid respectively. This study validates the antioxidant potential of the walnut kernels and the positive relationship between total phenolic content, total flavonoids and antioxidant activity.
RESUMEN
INTRODUCTION: Nuclear factor (erythroid-derived 2)-like factor 2 (Nrf2) is a transcription factor that regulates expression of many detoxification enzymes. Nrf2-antioxidant responsive element (Nrf2-ARE) signalling pathway can be a target for cancer chemoprevention. Glycyrrhiza glabra, common name, 'liquorice', is used as a sweetening and flavouring agent, and traditionally, to treat various ailments, and implicated to chemoprevention. However, its chemopreventive property has not yet been scientifically substantiated. OBJECTIVE: To assess the ability of liquorice root samples to induce Nrf2 activation correlating to their potential chemopreventive property. METHODS: The ability of nine methanolic extracts of liquorice root samples, collected from various geographical origins, to induce Nrf2 activation was determined by the luciferase reporter assay using the ARE-reporter cell line, AREc32. The antioxidant properties were determined by the 2,2-diphenyl-1-picryhydrazyl (DPPH) and the ferric-reducing antioxidant power (FRAP) assays. RESULTS: All extracts exhibited free-radical-scavenging property (RC50 = 136.39-635.66 µg/mL). The reducing capacity of ferrous ion was 214.46-465.59 µM Fe(II)/g. Nrf2 activation indicated that all extracts induced expression of ARE-driven luciferase activity with a maximum induction of 2.3 fold relative to control. These activities varied for samples from one geographical location to another. CONCLUSIONS: The present findings add to the existing knowledge of cancer chemoprevention by plant-derived extracts or purified phytochemicals, particularly the potential use of liquorice for this purpose. Copyright © 2016 John Wiley & Sons, Ltd.