Chemical characterization and biological activities of phenolic-rich fraction from cauline leaves of Isatis tinctoria L. (Brassicaceae) growing in Sicily, Italy

The present work focused on the evaluation of the antioxidant and cytotoxic activities of the phenolic-rich fraction (ItJ-EAF) obtained from cauline leaves collected in January from Isatis tinctoria L. (Brassicaceae) grown wild around Acireale (Sicily, Italy). The total phenolic, flavonoid and condensed tannin contents of the fraction were determined spectrophotometrically, whereas the phenolic profile was assessed by HPLC-PDA-ESI-MS analysis. A total of 20 compounds were positively identified and 12 out of them were never previously reported in I. tinctoria leaves. The fraction exhibited good radical scavenging activity in DPPH test (IC50 = 0.6657 ± 0.0024 mg/mL) and reducing power (3.87 ± 0.71 ASE/mL), whereas, it neither showed chelating activity nor was able to counteract H2O2 induced oxidative stress damage in Escherichia coli. The anti-proliferative effect was evaluated in vitro on two human anaplastic thyroid carcinoma cell lines (CAL-62 and 8505C) by MTT assay. At the highest tested concentration ItJ-EAF significantly reduced (80%) the growth of CAL-62 cells. No cytotoxicity against Artemia salina was observed. It can be concluded that I. tinctoria cauline leaves represent a source of phenolic compounds which could be potentially used as chemopreventive or adjuvant agents against cancer.