Two new flavonoids from Dracaena usambarensis Engl.
Investigations of the root extract of Dracaena usambarensis Engl. for anticancer principles led to the characterization of one new homoisoflavonoid, (3S)-3,4ʹ,5,6-tetrahydroxy-7-methoxyhomoisoflavanone (1) and a new retrodihydrochalcone, 4ʹ,4-dihydroxy-2,3-dimethoxydihydrochalcone (2) along with six previously reported compounds, including two homoisoflavonoids, 7-O-methyl-8-demethoxy-3-hydroxy-3,9-dihydropunctatin (3) and loureiriol (4); a phenolic amide, 3-(4ʹʹʹ-hydroxyphenyl)-N-[2ʹ-(4ʹʹ-hydroxyphenyl)-2ʹ-methoxyethyl]acrylamide (5); a spirostane, 25S-spirosta-1,4-dien-3-one (6) and two steroids, stigmasterol (7) and stigmasterol 3-O-β-D-glucopyranoside (8). The structures of 1-8 were determined using spectroscopic and spectrometric techniques. The absolute configurations of compounds 1 and 3 were achieved using circular dichroism spectroscopy. Using the resazurin reduction assay and doxorubicin as reference anticancer drug, 1 showed moderate cytotoxicity against drug sensitive CCRF-CEM but was inactive against all the other tested drug sensitive, resistance phenotypes and normal cells. The crude extract and 2-8 were inactive in the preliminary screening against CCRF-CEM and drug resistant CEM/ADR5000 cell lines. Interestingly, the activity of the standard drug, doxorubicin was comparable to those of inactive compounds against CEM/ADR5000 cells. Future studies should focus on structure modifications of 1-3, in order to obtain more potent analogues.
Circular dichroism, Absolute configuration, Natural products, Pharmaceutical