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.