Winter wild fennel leaves as a source of anti-inflammatory and antioxidant polyphenols

In the course of a screening program on the seasonal phenol composition of wild Mediterranean medicinal and aromatic plants, broadly used for culinary purposes, Foeniculum vulgare Mill. was the focus of the present study. Hydroalcoholic extracts from fennel freeze-dried leaves, collected in different seasons along 2012 and 2013 years, were quali-quantitatively analyzed through LC/MS/MS techniques. Winter extract contained, beyond several hydroxycinnamoyl quinic acids and flavonol glycosides, two chromone derivatives. Flavonol hexuronides were the main spring sample constituents. Phenol profile differences among the extracts influenced massively their bioactivity. When the antioxidant screening was performed, winter extract effectively scavenged DPPH and ABTS+ and reduced Fe3+. Although all the extracts did not show cytotoxicity, they were differently able to exert cytoprotection in H2O2-oxidized cell systems and to affect COX-2 gene expression in THP-1 cells. The most active one was winter extract, which inhibited COX-2 expression by 40%, whereas spring sample showed a weak pro-inflammatory capability.