Unprecedented Quassinoids from <i>Eurycoma longifolia</i>: Biogenetic Evidence and Antifeedant Effects

Abstract

Six new quassinoids (<b>1</b>-<b>6</b>) were isolated from the roots of <i>Eurycoma longifolia</i>, and their structures with absolute configurations were determined unambiguously by spectroscopic analyses and single-crystal X-ray crystallographic experiments. Compounds <b>1</b> and <b>2</b> are the first members of a new class of quassinoids with an unusual C₂₆ carbon skeleton. Compound <b>6</b> features a C₂₀ cage-like scaffold with an unprecedented densely functionalized 2,5-dioxatricyclo[5.2.2.0^4,8]undecane core. The discovery of the two C₂₆ quassinoids <b>1</b> and <b>2</b> has provided firm evidence for the better understanding the biogenetic process from C₃₀ triterpenoid precursors to quassinoids. Compound <b>5</b> exhibited significant antifeedant activity on the diamondback moth (DBM) larvae and excellent systemic absorption and accumulated properties in <i>Brassica chinensis</i>.