Bioactive constituents of Helianthus tuberosus (Jerusalem artichoke)

In a cytotoxicity-guided study using the MCF-7 human breast cancer cell line, nine known compounds, ent-17-oxokaur-15(16)-en-19-oic acid (1), ent-17-hydroxykaur-15(16)-en-19-oic acid (2), ent-15β-hydroxykaur-16(17)-en-19-oic acid methyl ester (3), ent-15-nor-14-oxolabda-8(17),12E-dien-18-oic acid (4), 4,15-isoatriplicolide angelate (5), 4,15-isoatriplicolide methylacrylate (6), (+)-pinoresinol (7), (−)-loliolide (8), and vanillin (9) were isolated from the chloroform-soluble subfraction of a methanol extract of the whole plant of Helianthus tuberosus collected in Ohio, USA. This is the first time that diterpenes have been isolated and identified from this economically important plant. The bioactivities of all isolates were evaluated using the MCF-7 human breast cancer cell line as well as a soybean isoflavonoid defense activation bioassay. The results showed that two germacrane-type sesquiterpene lactones, 5 and 6, are cytotoxic agents. While compounds 2, 3, 5 and 6 blocked isoflavone accumulation in the soybean, the norisoprenoid (−)-loliolide (8) was somewhat stimulatory of these defense metabolites.

Graphical abstractNine compounds, including three ent-kaurane diterpenoids, and an ent-norlabdane diterpenoid, were isolated from the methanol extract of the whole plant of Helianthus tuberosus. Among these compounds, two sesquiterpene lactones, 4,15-isoatriplicolide angelate (5), and 4,15-isoatriplicolide methylacrylate (6), showed cytotoxicity against the MCF-7 cell line. In a soybean isoflavonoid defense activation bioassay, 5 and 6, as well as two ent-kaurane diterpenoids 2 and 3, blocked isoflavone accumulation, while the norisoprenoid (−)-loliolide (8) showed a stimulatory effect to these defense metabolites .