A novel dimeric melampolide was isolated from the leaf rinse extract of Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson (Asteraceae), an Andean medicinal plant popularly known as yacón. Dimeric sesquiterpene lactones are rare in Asteraceae, especially melampolides. In addition, eight known melampolides and a new ester derivative were also isolated. All compounds were detected in glandular trichomes collected from the leaves and were analysed by HPLC. The anti-inflammatory properties of uvedalin, a known melampolide isolated in this study, were assessed in vitro by analyzing its effect on the DNA binding of the transcription factor NF-κB. These results were compared to those previously reported for the closely related melampolide enhydrin. Our data demonstrated that NF-κB DNA binding was inhibited in leukaemia and macrophage cells at an uvedalin concentration of 2.5 and 5 μM, respectively.

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A simple, reliable and rapid reversed-phase HPLC-PAD procedure for the characterisation and quantitative determination of the anti-diabetic sesquiterpene lactone enhydrin (1) from Smallanthus sonchifolius (yacón) has been evaluated and validated. The approach focused on the analysis of various leaf rinse extracts, as well as the glandular trichomes of intact leaves, in which 1 was the major compound detected. The best sample preparation of a rinse extract yielded 0.67 mg/mL of 1, whilst a rapid rinse of a small piece of one dried leaf gave 0.09 mg/mL of 1; the highest concentration obtained from a glandular extract was 0.07 mg/mL. The dried leaves of S. sonchifolius were found to contain a total of 0.97% of 1.