Seasonal variation in phenolic composition and antioxidant and anti-inflammatory activities of Calamintha nepeta (L.) Savi

Calamintha nepeta (L.) Savi (Lamiaceae) is a small culinary and medicinal aromatic herb, native to the Mediterranean region, traditionally used for its diaphoretic, expectorant, febrifuge and stomachic properties. In order to carry out a thorough chemical and biological screening of the plant and to explore phenophase influence on its polyphenol content, samples of the plant were collected at different phases during its life cycle (July/October 2012 and January/April 2013). Each sample, previously extracted using a hydroalcoholic solution, was analyzed for its phenol contents through LC-DAD-ESI-MS/MS techniques. Acacetin and caffeic acid derivatives were the main constituents and the relative abundance of each identified metabolite seemed to be strongly collection time dependent. The evaluation of the antioxidant capacity of the investigated hydroalcoholic extracts was carried out performing different tests. Relative Antioxidant Capacity Index (RACI) was also calculated. Although extract from the summer collection exerted the highest antioxidant capability in cell-free systems, when cytoprotective and anti-inflammatory activities were assessed, extract from the winter collection was the most active sample. In particular, it was capable to inhibit COX-2 synthesis by 40.10%; dexamethasone, used as positive control, exerted a similar activity. Comparing phenol profiling data to bioactivity ones, it was highlighted that the winter extract contained an amount of acacetin and its derivatives nearly four times than those of caffeic acid derivatives.