Cytotoxic and Antimalarial Amaryllidaceae Alkaloids from the Bulbs of Lycoris radiata

Phytochemical investigation of the 80% ethanol extract of the bulbs of Lycoris radiata resulted in the isolation of five new Amaryllidaceae alkaloids: (+)-5,6-dehydrolycorine (1), (+)-3α,6β-diacetyl-bulbispermine (2), (+)-3α-hydroxy-6β-acetyl-bulbispermine (3), (+)-8,9-methylenedioxylhomolycorine-N-oxide (5), and 5,6-dihydro-5-methyl-2-hydroxyphenanthridine (7), together with two known compounds, (+)-3α-methoxy-6β-acetylbulbispermine (4) and (+)-homolycorine- N-oxide (6). Structural elucidation of all the compounds were 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. Alkaloid 1 showed potent cytotoxicity against astrocytoma and glioma cell lines (CCF-STTG1, CHG-5, SHG-44, and U251), as well as HL-60, SMMC-7721, and W480 cell lines with IC(50) values of 9.4–11.6 μM. Additonally, compound 1 exhibited antimalarial activity with IC(50) values of 2.3 μM for D-6 strain and 1.9 μM for W-2 strain of Plasmodium falciparum.