New sesquiterpene glycoside ester with antiprotozoal activity from the flowers of Calendula officinalis L

Continued chromatographic investigation of Calendula officinalis flowers led to the isolation of two sesquiterpenes, including one new, viridiflorol-10-O-beta-quinovopyranoside-2`-O-(3``-methyl-2``-pentenoate) (1), along with a previously reported compound viridiflorol-10-O-beta-fucopyranoside-2`-O-(3``-methyl-2``-pentenoate) (2). The new compound 1 was tested for antiprotozoal activity against Leishmania donovani Amastigote/THP1 and Trypanosoma brucei and it showed IC50 values of 3.57 and 7.84 mu g/mL, respectively, while compound 2 exhibited no activity at the highest concentration tested 10 mu g/mL.