Reactive oxygen species (ROS)-induced cell damage is inevitable and severe and is involved in numerous diseases, including cancer. Reducing oxidative stress is an important strategy of chemoprevention. Anthocyanins are naturally occurring flavonoids that show multiple benefits including free radical scavenging activities. Our objective was to study the anthocyanins isolated from eggplant peel on antioxidant effectiveness as compared to other delphinidin derivatives in cell-free systems and HT-29 and HCT-116 cell lines.The delphinidin-3-(p-coumaroylrutinoside)-5-glucoside (nasunin) from eggplants was purified with Amberlite XAD-7HP, Sephadex LH-20 and preparative HPLC, and analyzed via LC-MSn. The deacylated nasunin was obtained by alkaline hydrolysis. Other 5 non-acylated delphinidin-derviatives were purchased for a total of 7 delphinidin derivatives: delphinidin (dp), dp-3-glucoside, dp-3-rutinoside, dp-3,5-diglucoside, dp-3-rutinoside-5-glucoside (deacylated nasunin), dp-3-sambubioside, delphinidin-3-(p-coumaroylrutinoside)-5-glucoside (nasunin). Cyanindin and pelargonidin were used as reference anthocyanins.  All Dp-derivatives were evaluated for their direct antioxidant activity (HOSC, hydroxyl radical scavenging capacity; ORAC, oxygen radical absorbing capacity), cellular reactive oxygen species (ROS) level, DNA damage and protein expression of NAD(P)H: quinone oxidoreductase 1 (NQO1), ?-glutamylcysteine ligase (? -GCL) and glutathione reductase (GSR)  in HT-29/HCT-116.Delphinidin derivatives including nasunin did not show a high ability to scavenge free radicals in ORAC or HOSC assay compared to pelargonidin and cyanidin derivatives in vitro. Additionally, Delphinidin aglycon exhibited the lowest antioxidant values among tested delphinidin derivatives. Delphinidin-derivatives significantly stimulated the GSR expression in both cell lines, to a great extend in HT-29.  Except for dp-3-sambubioside, all others appeared to protect the DNA from menadione-induced damage.The results showed delphinidin derivatives appeared to be potent radical scavengers in vitro via increasing of GSR expression and protecting DNA damage.  The eggplant peel could be considered as a source of potent antioxidants and as a potential natural colorant. However, further research in different systems will be needed in future.

Effect of glycosylation and acylation patterns of delphinidin derivatives on their antioxidant activities in cell free system and HT-29 and HCT-116 cell lines

246th National Meeting (2013)

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