1 research outputs found
Antibacterial Labdane Diterpenoids from Vitex vestita
A large-scale in vitro screening
of tropical plants using an antibacterial
assay permitted the selection of several species with significant
antibacterial activities. Bioassay-guided purification of the dichloromethane
extract of the leaves of the Malaysian species Vitex
vestita, led to the isolation of six new labdane-type
diterpenoids, namely, 12-epivitexolide A (<b>2</b>), vitexolides
B and C (<b>3</b> and <b>4</b>), vitexolide E (<b>8</b>), and vitexolins A and B (<b>5</b> and <b>6</b>), along
with six known compounds, vitexolides A (<b>1</b>) and D (<b>7</b>), acuminolide (<b>9</b>), 3Ī²-hydroxyanticopalic
acid (<b>10</b>), 8Ī±-hydroxyanticopalic acid (<b>11</b>), and 6Ī±-hydroxyanticopalic acid (<b>12</b>). Their
structures were elucidated on the basis of 1D and 2D NMR analyses
and HRMS experiments. Both variable-temperature NMR spectroscopic
studies and chemical modifications were performed to investigate the
dynamic epimerization of the Ī³-hydroxybutenolide moiety of compounds <b>1</b>ā<b>4</b>. Compounds were assayed against a
panel of 46 Gram-positive strains. Vitexolide A (<b>1</b>) exhibited
the most potent antibacterial activity with minimal inhibitory concentration
values ranging from 6 to 96 Ī¼M, whereas compounds <b>2</b> and <b>6</b>ā<b>9</b> showed moderate antibacterial
activity. The presence of a Ī²-hydroxyalkyl-Ī³-hydroxybutenolide
subunit contributed significantly to antibacterial activity. Compounds <b>1</b>ā<b>4</b> and <b>6</b>ā<b>9</b> showed cytotoxic activities against the HCT-116 cancer cell line
(1 < IC<sub>50</sub><i>s</i> < 10 Ī¼M) and human
fetal lung fibroblast MRC5 cell line (1 < IC<sub>50</sub><i>s</i> < 10 Ī¼M for compounds <b>1</b>,<b> 2</b>,<b> 7</b>,<b> 8</b>, and <b>9</b>)