Antioxidant activity and phenolic content of extracts from different Pterospartum tridentatum populations growing in Portugal

In the present study, aerial parts of Pterospartum tridentatum plants, collected in three locations in Portugal, at different vegetative stages, were evaluated for their total phenolic content and the antioxidant activity of aqueous extracts. The influence of the seasonal variation in the yield and composition of the extracts was evaluated, in order to select the most appropriate harvest season. Among the populations assayed, the extraction yields have some differences with the harvest period but the highest yield extraction was obtained in the flowering season, using flowers (19.4g/100g plant dry mass) and the lowest extraction yield was also obtained in the same period but using stems. The antioxidant activity of the solid extracts of Pterospartum tridentatum aerial parts, was determined by the radical scavenging activity method using 2,2-diphenyl-1-picrylhydrazyl radical (DPPH). The greatest DPPH radical scavenging activity was observed in the flowering period (3.6 mMTrolox/Kg dry mater), but no significant differences for the dormancy period. According to these results, we can choose the harvest season more favorable. The total phenolic content (TP) of the extracts was evaluated by measuring the absorbance at 280 nm and the values ranged from 270.7 to 402.9 mg gallic acid equivalents per g dry matter. The vegetative stage did not influence this total phenolic content. From preliminary experiments, it is also anticipated a significant antimicrobial activity of the solid extracts against bacteria and fungus