Bioactive 6<i>S</i>‑Styryllactone Constituents of <i>Polyalthia parviflora</i>
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Abstract
Parvistones A–E (<b>1</b>–<b>5</b>), five new styryllactones possessing a rare
α,β-lactone moiety and a 6<i>S</i> configuration,
were isolated from a methanolic extract of <i>Polyalthia parviflora</i> leaves. The structures and the absolute configuration of the isolates
were elucidated using NMR spectroscopy, specific rotation, circular
dichroism, and X-ray single-crystal analysis. Compounds <b>8</b>, <b>9</b>, <b>11</b>, and <b>12</b> were isolated
for the first time. The results were supported by comparing the data
measured to those of 6<i>R</i>-styryllactones. Moreover,
a plausible biogenetic pathway of the isolated compounds was proposed.
The structure–activity relationship of the compounds in an
in vitro anti-inflammatory assay revealed the 6<i>S</i>-styryllactones
to be more potent than the 6<i>R</i> derivatives. However,
the effect was opposite regarding their cytotoxic activity. In addition,
6<i>S</i>-styrylpyrones isolated showed more potent anti-inflammatory
and cytotoxic activity when compared to the 1<i>S</i>-phenylpyranopyrones
obtained