Paliasanines A-E, 3,4-Methylenedioxyquinoline Alkaloids Fused with a Phenyl-14-oxabicyclo[3.2.1]octane Unit from Melochia umbellata var. deglabrata

Abstract

Five new quinoline alkaloids, paliasanines A-E (<b>1</b>-<b>5</b>), and 17 known compounds (<b>6</b>-<b>22</b>) were isolated from a methanol extract of <i>Melochia umbellata</i> var. <i>deglabrata</i> leaves. Their chemical structures were elucidated by analysis of HRMS and 1D and 2D NMR spectroscopic data. Compounds <b>1</b>-<b>5</b> are the first naturally occurring 3,4-methylenedioxyquinolines incorporating an oxabicyclo[3.2.1]octane unit. Compounds <b>6</b> and <b>7</b> displayed selective cytotoxicity (IC₅₀ 5.9-8.4 μM) against A549 and MCF-7 cell lines, while compounds <b>1</b>-<b>5</b> were not active. Compounds <b>1</b>-<b>3</b> did not exhibit an anti-HIV effect in MT4 cells, although the related quinolone derivative waltherione A exhibited significant activity. These preliminary results indicate that the 3-methoxy-4-quinolone skeleton might be preferred for both antiproliferative and anti-HIV activities.

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