Turmeric sesquiterpenoids: expeditous resolution, comparative bioactivity, and a new bicyclic turmeronoid

An expeditious strategy to resolve turmerone, the lipophilic anti-inflammatory principle of turmeric (Curcuma longa), into its individual bisabolane constituents (ar-, α-, and β-turmerones, 2−4, respectively) was developed. The comparative evaluation of these compounds against a series of anti-inflammatory targets (NF-κB, STAT3, Nrf2, HIF-1α) evidenced surprising differences, providing a possible explanation for the contrasting data on the activity of turmeric oil. Differences were also evidenced in the profile of more polar bisabolanes between the Indian and the Javanese samples used to obtain turmerone, and a novel hydroxylated bicyclobisabolane ketol (bicycloturmeronol, 8) was obtained from a Javanese sample of turmeric. Taken together, these data support the view that bisabolane sesquiterpenes represent an important taxonomic marker for turmeric and an interesting class of antiinflammatory agents, whose strict structure−activity relationships are worth a systematic evaluation.