Anti-diabetic, anti-inflammatory activities and toxicology of yacon (Smallanthus sonchifolius, Asteraceae)

Abstract

Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson (Asteraceae) is a perennial herb popularly known as yacón. It is originary of the Andes, where its tuberous roots are used as food and its leaves are used in the folk medicine for the treatment of diabetes. Yacón is sold in many countries for its inulin and fructan-reserving tuberous roots, while the leaves are commercialized to prepare medicinal teas. The hypoglycemic activity of the aqueous extract of the leaves of this plant has been demonstrated in a recent study. Further studies had shown that extracts of this plant reduce the glucose production in hepatocytes of rats and present antioxidant activity in vitro. Studies carried out in our laboratory have demonstrated that the in vitro anti-inflammatory activity is due to the inhibition of the transcription factor NF-κB by sesquiterpene lactones isolated from the leaf rinse extract. Phytochemical investigations of the foliar extracts have shown the presence of phenolic compounds, sesquiterpene lactones, kaurane-type diterpenes and flavonoids. There is a great amount of sites in the Internet recommending the use of yacón for the treatment of diabetes. Its utilization as food or in the traditional medicine is growing in some countries, including Brazil. However, studies on the medicinal efficacy of specimens cultivated in Brazil are scarce, while studies which prove the lack of toxicity both in prolonged and in large amount use of the tea of the leaves are do not exist. It has been shown that compounds in the leaves of yacón present in vitro anti-inflammatory activity, however this activity was poorly investigated and there are not any studies concerning this activity in vivo. Thus, the aim the present work is to evaluate the antidiabetic effect of the yacón on Brazilian growth conditions, to analyze if the extracts present toxicity as well as to better explore its anti-inflammatory action. Moreover, the characterization of the main compounds responsible for the biological activities of yacón will be carried out.