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-β-quinovopyranoside-2`-O-(3``-methyl-2``-pentenoate) (1), along with a previously reported compound viridiflorol-10-O-β-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 µg/mL, respectively, while compound 2 exhibited no activity at the highest concentration tested 10 µg/mL.