Highly oxidized sesquiterpenes from the fruits of Illicium lanceolatum A. C. Smith

Abstract

Ten undescribed highly oxidized sesquiterpenes and six known sesquiterpenes were isolated from H₂O-soluble part of the fruits of Illicium lanceolatum A. C. Smith. The structures of undescribed compounds were elucidated by interpretation of spectroscopic data, and the absolute configurations of 2α-hydroxyneoanisatinic acid, (1R,5R,6S,7R,9R,10R)-3,4-dehydro-12-hydroxy-floridanolide, and (1R,4S,5R,6S,7S,9S)-1-deoxy-13-hydroxymerrilactone B were determined by the single-crystal X-ray diffraction analysis. Illilanceolatin A was the first example of a seco-prezizaane type sesquiterpene with a hemiacetal moiety located at C-10. 2α-Hydroxyneoanisatinic acid and anisatinic acid were two naturally occurring undescribed seco-prezizaane type sesquiterpenes with a 5/5/6 tricyclic carbon skeleton. Plausible biosynthetic pathways of the isolated polycyclic and highly oxidized sesquiterpenes derived from the intermediate allo-cedrane were proposed. (1R,5R,6S,7R,9R,10R)-3,4-dehydro-12-hydroxy-floridanolide, 1,3-dihydroxyneoanisatin, and 2α-hydroxyneoanisatin displayed neuroprotective effects with protection rates of 19.9, 22.7 and 24.3% at 10 μM, respectively. Additionally, the preliminary acute toxicity of anisatinic acid was also evaluated.

Keywords: Acute toxicity; Illicium lanceolatum A. C. Smith (Illiciaceae); Illilanceolatin A; Neuroprotective effects; Seco-prezizaane sesquiterpenes.