Alkaloids from Lycoris aurea and their cytotoxicities against the head and neck squamous cell carcinoma

Phytochemical investigation of the 80% EtOH extract of the bulbs of Lycoris aurea led to the isolation of six new alkaloids, 2-demethyl-isocorydione (1), 8-demethyl-dehydrocrebanine (2), 1-hydroxy-anhydrolycorin-7-one (3), (+)-1,2-dihydroxy-anhydrolycorine N-oxide (4), 5,6-dihydro-5-methyl-2-hydroxyphenanthridine (5), and (+)-8-hydroxy-homolycorine-α-N-oxide (6), and together with two known compounds, isocorydione (7) and anhydrolycorin-7-one (8). Structural elucidation of all the compounds was performed by spectral methods such as 1D and 2D ((1)H-(1)H COSY, HMQC, and HMBC) NMR spectroscopy, in addition to high resolution mass spectrometry. All the alkaloids were in vitro evaluated for their cytotoxic activities against seven tumor cell lines of the head and neck squamous cell carcinoma and anti-inflammatory activities. Compounds 1, 2, 6, and 7 exhibited significant cytotoxicities against all the tested cell lines. Moreover, alkaloids 1, 2, and 7 possessed selective inhibition of Cox-2 (>85%).