Phenylethanoid Glycosides From <i>Clerodendrum bungei</i> and Their Cytotoxic Activities

One new phenylethanoid glycoside, named bungaside A (1), along with six known phenylethanoid glycosides (2-7), were isolated from the dried aerial parts of Clerodendrum bungei Steud. Their structures were elucidated from extensive spectroscopic analysis and hydrolysis. All the isolates were evaluated for their anti-tumor effects against H460, A549, and HepG2 cancer cell lines. Compound 7 showed moderate activity against all cell lines, with the half-maximal inhibitory concentration (IC₅₀) values ranging from 2.25 to 13.13 µM. Meanwhile, compounds 3 and 6 displayed weak activities on A549 with the IC₅₀ values of 11.61 ± 1.38 and 16.68 ± 1.16 µM. Compounds 3 and 6 displayed moderate activities on H460 with the IC₅₀ values of 5.10 ± 0.12 and 7.23 ± 0.65 µM, respectively. Besides, the preliminary structure-activities relationship showed that the skeleton of phenylethanoid glycosides containing a monosaccharide may have a stronger anticancer effect than their corresponding disaccharides, and the increase in the methylation of the hydroxyl group on the aromatic ring is also an important reason decrease in activity.