Santolina impressa, a Portuguese endemic species: Inhibition of acetylcholinesterase, antioxidant activity and cell toxicity

Abstract

Santolina impressa Hoffmanns & Link is an endemic Asteraceae species that occurs in the dunes throughout southwestern Portugal, from the estuary of Sado River to Cape Sines [1]. Although the species was used in folk medicine for a wide range of ailments, particularly for digestive disorders [2] no phytochemical data were available. This study aims to evaluate the inhibition of acetylcholinesterase (AChE) and the antioxidant capacity of the aqueous extracts (decoctions) from S. impressa, relating these activities with the extracts chemical composition. Biological activities were assessed before and after in vitro gastrointestinal metabolism by action of gastric and pancreatic artificial juices [3] and, the extracts cytotoxicity was evaluated using Caco-2 cells, a model of intestinal cells. In the decoctions from the aerial parts of S. impressa, chlorogenic acid was one of the main components together with dicaffeoylquinic acids and homoorientin. Decoctions from flowers and leaves/stems showed AChE high inhibition capacity, IC50 of 329 µg/ml and 579 µg/ml, respectively. The antioxidant activity, measured using the DPPH test, gave an effective concentration (EC50) of 12.9 µg/ml and 14.7 µg/ml for flowers and leaves/stems, respectively. Biological activities were kept constant after in vitro gastrointestinal digestion and the HPLC analysis did not indicate any change in the extracts composition. Decoctions did not show toxicity to Caco-2 cells. The high antioxidant activity detected, similar to the antioxidant capacity of standards used in food industry [4] and the AChE inhibition activity found must due to the presence of chlorogenic acid and dicaffeolyquinic acids derivatives [4]. In conclusion, these extracts can pass through the gastrointestinal tract without losing its biological activity and be absorbed in the small intestine without being toxic to the cells. The results reported may explain, in part, the ethnobotanical uses of S. impressa for digestive problems.