Cytotoxic
Bisbenzylisoquinoline Alkaloids from <i>Stephania epigaea</i>
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Abstract
Six new bisbenzylisoquinoline alkaloids
(<b>1</b>–<b>6</b>) and seven known compounds (<b>8</b>–<b>14</b>) were isolated from the tubers of <i>Stephania epigaea</i>, in addition to the major alkaloid, cepharanthine
(<b>7</b>). The structures of <b>1</b>–<b>6</b> were elucidated
by combined spectroscopic data analysis and chemical methods, with
their configurations determined from their optical rotation values
and confirmed using circular dichroism. Compounds <b>1</b>–<b>6</b> belong to the oxyacanthine type of bisbenzylisoquinoline
alkaloids and have a rare methylenedioxy substituent. Compound <b>1</b>, a dimer composed of benzylisoquinoline and seco-aristolactam
units, represents a new type of bisbenzylisoquinoline alkaloid, while
compounds <b>3</b>–<b>6</b> are bisbenzylisoquinoline <i>N</i>-oxides. These compounds were evaluated for their in vitro
cytotoxicities against six human cancer cell lines (A-549, ECA109,
HL-60, MCF-7, SMMC-7721, and SW480). Cepharanthine (<b>7</b>), the major component of <i>S. epigaea</i>, exhibited
cytotoxicity against all of these cancer cell lines except ECA109,
while its known analogue, <b>10</b>, displayed cytotoxicity
against all six cancer cell lines