Phytochemical investigation on the barks of Betula platyphylla var. japonica (Betulaceae) was carried out, resulting in the isolation and identification of three new triterpenoids, 27-O-cis-caffeoylcylicodiscic acid (1), 27-O-cis-feruloylcylicodiscic acid (2), and 27-O-cis-caffeoylmyricerol (3), along with six known triterpenoids, obtusilinin (4), winchic acid (5), 27-O-trans-caffeoylcylicodiscic acid (6), uncarinic acid E (7), myriceric acid B (8), and 3-O-trans-caffeoyloleanolic acid (9). The structures of the new compounds were elucidated by extensive spectroscopic methods, including 1D- and 2D-NMR, and HR-ESI-MS. All of the isolated compounds were evaluated for cytotoxicity against four human tumor cell lines (A549, SK-OV-3, SK-MEL-2, and Bt549). Compounds 2, 6, 8, and 9 exhibited potent cytotoxicity against all of the tumor cells tested (IC50 < 10.0 μm), while compounds 3, 4, 5, and 7 showed moderate cytotoxicity against all of the tumor cells tested (IC50 < 20.0 μm).
Keywords: Betula platyphylla; Betulaceae; Cytotoxic activities; Triterpenoids.
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