Phytotoxic Neocassane Diterpenes fromEragrostis plana

Abstract

Five new neocassane-like diterpenes (1–5) were isolated from the roots of Eragrostis plana. Their structures were elucidated by spectroscopic data, and the absolute configurations of the representative compounds neocassa-12(17),15-dien-3-one (2) and neocassa-12(13),15-diene-3,14-dione (5) were assigned by vibrational circular dichroism. The phytotoxic activity of compounds 3, 4, and 5 was evaluated against the germination and growth of Ipomoea grandifolia and Euphorbia heterophylla. Compound 4 exhibited the most potent activity for growth variables, resulting in the smallest radicle length of I. grandifolia and in the smallest aerial part length of E. heterophylla. Compound 5 reduced the germination speed index more effectively than the herbicide glyphosate (Roundup).

Biology of the invasive species Eragrostis plana in Southern Brazil: What have we learned and how may this help us manage it?

“…Additional work seeking to isolate the compounds responsible for E. plana allelopathy resulted in eight neocassane diterpenoids (Favaretto et al, 2019; Klein Hendges et al, 2020). Three of these, isolated from E. plana roots, were phytotoxic in Ipomoea grandifolia (Dammer) O'Donnell and Euphorbia heterophylla L. In addition, the three compounds together inhibit weed growth ( Lemna paucicostata L.) and one exhibited fungicidal activity against Colletotrichum fragariae , C. acutatum , and C. gloeosporioides (Favaretto et al, 2019).…”

“…Of the five remaining terpenes, one demonstrated powerful phytotoxic activity on the growth of I. grandifolia roots and E. heterophylla shoots. Likewise, another compound reduced the germination index of E. heterophylla even more effectively than the glyphosate herbicide (Klein Hendges et al, 2020). Moreover, allelopathic potential increases with nitrogen fertilisation, and phenolic compound concentration increases in the reproductive stage (Cecchin et al, 2017).…”

Vibrational Circular Dichroism for the Assignment of Absolute Configuration of Natural Products in Brazil

“…VCD was also proven to be a powerful technique to distinguish epimeric terpenes. A good example is the case of neocassane diterpenes from Eragrostis plana Nees, Poaceae (Hendges et al 2020). ,15-dien-3-one (7) had its relative configuration determined by NMR experiments; however, the configuration at C-13 remained unassigned (Fig.…”