Chemical Constituents of Primulina eburnea (Gesneriaceae) and Their Cytotoxic Activities

Two new ursane‐type triterpenes, eburnealactones A and B (1 and 2), one new flavonoid, eburneatin A (6), and one new phenylethanoid glycoside, chiritoside D (7), along with 9 known compounds (3–5, 8–13) were isolated from the whole plant of Primulina eburnea. Their structures were elucidated by comprehensive spectroscopic data analysis (IR, UV, NMR, and HR‐ESI‐MS). All the compounds were evaluated for their cytotoxic activities. Compound 1 showed significant cytotoxic activities against MKN‐45 cell lines and 5637 cell lines with the IC50 values of 9.57 μM and 8.30 μM, respectively. Compound 1 exhibited moderate cytotoxic activities against A549 and PATU8988T cell lines with the IC50 values of 30.70 μM and 38.22 μM, respectively. Compound 6 exhibited moderate cytotoxic activities against MKN‐45, HCT116, PATU8988T, 5637 and A‐673 cell lines with the IC50 values of 19.69 μM, 16.44 μM, 18.07 μM, 11.51 μM and 18.15 μM, respectively. Compound 5 showed moderate cytotoxic activities against A549 cell lines with the IC50 values of 24.06 μM.