Iridoid Glycosides from the Twigs of Sambucus williamsii var. coreana and Their Biological Activities

Six new iridoid glycosides, sambucusides A-F (1-6), and two known derivatives (7 and 8) were isolated from a methanol extract of the twigs of Sambucus williamsii var. coreana. Their chemical structures were elucidated by spectroscopic methods, including NMR (¹H and ¹³C NMR, ¹H-¹H COSY, HMQC, HMBC, and NOESY) and HRMS. All isolated compounds (1-8) were evaluated for their antiproliferative activities against four human cancer cell lines (A549, SK-OV-3, SK-MEL-2, and Bt549). Their effects on nitric oxide (NO) production in lipopolysaccharide (LPS)-activated BV-2 cells and their neuroprotective effects through induction of nerve growth factor (NGF) in C6 glioma cells were also examined. Compounds 2, 3, and 5 showed cytotoxic effects (IC₅₀ 1.3-8.7 μM) against the SK-MEL-2 and Bt549 cell lines and inhibitory effects on NO production (IC₅₀ of 0.9, 1.3, and 1.2 μM, respectively). Compounds 2, 4, and 8 exhibited NGF-releasing effects (147.0 ± 5.8%, 158.7 ± 5.2%, and 152.6 ± 7.3%, respectively).