Chemical Defense of Yacón (Smallanthus sonchifolius) Leaves against Phytophagous Insects: Insect Antifeedants from Yacón Leaf Trichomes

Abstract

<jats:p>Yacón is a perennial crop with high insect resistance. Its leaves have many glandular trichomes, which may be related to pest resistance. In order to collect the constituents of glandular trichomes, leaves were rinsed using dichloromethane (DCM) to obtain the rinsate, and the plant residues were subsequently extracted by DCM to obtain a DCM extract containing the internal constituents of yacón leaves. Biologic evaluations revealed that insect antifeedant activity was stronger for the rinsate than for the DCM extract against the common cutworm. The major constituents of rinsate were isolated by silica gel flash chromatography and were identified as sesquiterpene lactones (SLs), uvedalin (1) and enhydrin (2) and uvedalin aldehyde (3), collectively known as melampolides. Although SLs 1 and 2 exhibited remarkably strong insect antifeedant activity, SL 3 and reduced corresponding derivatives (4 and 5) of 1 and 2 exhibited moderate insect antifeedant activity. Additionally, the two analogs, parthenolide (6) and erioflorin (7) showed moderate insect antifeedant activity. The results indicate that the substituent patterns of SLs may be related to the insect antifeedant activities. The insect antifeedant activities of SLs 1 and 2 were similar to that of the positive control azadirachtin A (8), and thus these natural products may function in chemical defense against herbivores.</jats:p>

Quantification of Enhydrin and Uvedalin in the Ethanolic Extract of Smallanthus sonchifolius Leaves Validated by the HPLC Method

“…Sesquiterpene lactones, enhydrin, and uvedalin are active compounds in yacon leaves that have various activities. These compounds are collected in glandular trichomes on the leaf’s surface [ 21 ]. Rinse extraction is a suitable method for extracting compounds on a leaf’s surface.…”

“…The enhydrin and uvedalin compounds are the chemotype and subtype compounds used in determining the quality of yacon leaf extract as a traditional medicinal ingredient [ 19 ]. They are mostly stored in the trachoma glandular on the leaf’s surface [ 21 ]. However, the content of these two compounds can deviate depending on the growth location.…”

The identification of potato genotype diversity based on morpho-agronomy and nutritional traits in the highland areas of Papua, Indonesia

“…There is an indication that many glandular trichomes are related to pest resistance. According to Tsunaki and Morimoto (2020), a secondary metabolite isolated from the trichomes of Smallanthus sonchifolius (Poepp. & Endl.)…”