Two Unusual Rearranged Flavan Derivatives from Narcissus tazetta var. chinensis

Abstract Two unusual rearranged flavan derivatives with a rare bicyclo[3.3.1]non‐3‐ene‐2,9‐dione ring, tazettone A ( 1 ) and tazettone B ( 2 ), together with five known flavans, 3 – 7 , were isolated from the bulbs of Narcissus tazetta var. chinensis Roem . The structures of two new compounds were elucidated by spectroscopic analyses, including 1D‐ and 2D‐NMR spectroscopy. All of the isolated compounds were evaluated for their cytotoxicities against four human tumor cell lines A549, HCT116, SK‐BR‐3, and HepG2. Compounds 1 and 2 were almost inactive against all tested cell lines, while compounds 3 – 7 exhibited moderate or weak cytotoxicities against the tested cell lines.