Isolation, characterization and biological activities of phenolics from the roots bark of Morus alba

An undescribed coumarin–limonene hybrid (morusalin A, 1), an unreported steppogenin–limonene hybrid (morusalin B, 2), and three undescribed isoprenylated flavonoids (morusalins C–E, 3–5), along with forty-one known ones (6–46), were isolated from the dried roots bark of Morus alba. Their structures with absolute configurations were elucidated by detailed interpretation of NMR spectroscopy, mass spectrometry, single-crystal X-ray diffraction, and ECD calculations. In addition, all these isolated compounds were assayed for their inhibitory activity against lipopolysaccharide (LPS)-induced nitric oxide (NO) production in murine macro-phage RAW 264.7 cells and for their cytotoxic activities against human colon cancer (HCT 8) and hepatoma (HepG 2) cells. Moreover, a biosynthetic pathway for the formation of compounds 1–6 is also proposed.