Antioxidant activity and verbascoside content in extracts from two uninvestigated endemic Plantago spp

This work describes for the first time the antioxidant activity of extracts from wild plants and in vitro cultures of two previously uninvestigated Plantago spp. endemic to Portugal, Plantago algarbiensis Samp. and Plantago almogravensis Franco. The well-known and widely distributed species Plantago lagopus L. was also studied for comparison. Although the extracts from the three species exhibited radical scavenging and iron-reducing properties, the extracts from the two endemic species showed greater activity irrespectively of plant material source. Both P. algarbiensis extracts showed similar antioxidant activity whereas, in the case of P. almogravensis higher activity was observed for extracts from wild plants compared to extracts from in vitro cultures. Liquid chromatography–diode array detection analyses indicate verbascoside as a major constituent of all extracts and the highest content was obtained from in vitro cultures of P. algarbiensis. In addition, a high correlation between the antioxidant activity measured with three methods and the total phenolic content was found, but no correlation was observed between antioxidant activity and verbascoside content. The results suggest that P. algarbiensis and P. almogravensis are sources of health-beneficial phytochemicals and indicate that in vitro cultures represent a promising alternative for the biosynthesis of verbascoside.