13C nuclear magnetic resonance studies of sesquiterpenes, anisatin and neoanisatin

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

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.

A prezizaane sesquiterpene from Illicium angustisepalum

The prezizaane sesquiterpene angustisepalin has been isolated from the aerial parts of Illicium angustisepalum, and its structure determined by 2D-NMR spectroscopy. Angustisepalin is formally the 10-benzoyl ester of neomajucin, previously reported from Illicium majus.