Forsythia suspensa (Thunb.) Vahl leaves have been consumed in China as a health-promoting functional tea for centuries. Three new polyhydroxytriterpenoid glycosides named suspensanosides A-C (1-3), seven known polyhydroxytriterpenoids (4-10), and 12 known phenolics (11-22) were identified from F. suspensa leaves. Compounds 1-10, 15-17, and 22 have not been found in the Forsythia genus previously, whereas compound 14 was first reported to be isolated from the leaves of F. suspensa. All isolates were tested for their antiproliferative activities on BGC-823 and MCF-7 human tumor cell lines, whereas all phenolics were further investigated for their antioxidant activities by a DPPH assay. The results clearly demonstrate that triterpenoids, especially ursane-type triterpenoids, and the diverse phenolic components are crucial for the beneficial effects of F. suspensa leaves.
Keywords: Forsythia suspensa (Thunb.) Vahl; antioxidant activity; antiproliferative activity; leaves; phenolics; triterpenoids.