Cage-Monoterpenoid Quinoline Alkaloids with Neurite Growth Promoting Effects from the Fruits of <i>Melodinus yunnanensis</i>

Abstract

Meloyunnanines A-C, three alkaloids with an unprecedented skeleton, were isolated from fruits of <i>Melodinus yunnanensis</i>. The structures featuring a caged-6/6/5/6/5/5 ring system were elucidated by the analysis of comprehensive spectroscopic and X-ray data. Biosynthetically, meloyunnanines A-C were assigned to monoterpenoid quinoline alkaloids (MQAs), derived from monoterpenoid indole alkaloids through oxidation and rearrangement. These compounds together with three known <i>Melodinus</i> MQAs were evaluated for their neurotrophic activity and scandine <i>N</i>⁴-oxide exhibited significant effect.