C-geranyl compounds from Paulownia tomentosa fruits.

Five geranylflavonoids, one prenylated flavonoid, and a simple flavanone were isolated from an ethanolic extract of Paulownia tomentosa fruit. Tomentodiplacol (1), 3'-O-methyl-5'-methoxydiplacol (2), 6-isopentenyl-3'-O-methyltaxifolin (3), and dihydrotricin (4) are reported from a natural source for the first time and 3'-O-methyldiplacone (6) for the first time from the genus Paulownia. The structures of the compounds were determined by mass spectrometry, including HRMS, and by 1D and 2D NMR spectroscopy. The cytotoxicity and DPPH (2,2-diphenyl-1-picrylhydrazyl)-quenching activity of some of these compounds were tested, with diplacone proving to be the best antioxidant, although the most cytotoxic compound.