2 research outputs found
MDN-0185, an Antiplasmodial Polycyclic Xanthone Isolated from <i>Micromonospora</i> sp. CA-256353
A potent antiplasmodial polycyclic
xanthone, MDN-0185 (<b>1</b>), was isolated from an unidentified
species of the genus <i>Micromonospora</i>. The planar structure
of <b>1</b> was
established as a seven-ring polycyclic xanthone with partial structures
very similar to two known natural products, namely, xantholipin and
Sch 54445. Using ROESY correlations, the relative stereochemistry
of the two independent stereoclusters of compound <b>1</b> could
be determined. Mosher analysis and comparison of the specific rotation
of compound <b>1</b> with that of xantholipin allowed the determination
of its absolute configuration. Compound <b>1</b> exhibited an
IC<sub>50</sub> of 9 nM against <i>Plasmodium falciparum</i> 3D7 parasites
Isolation and Structural Elucidation of Cyclic Tetrapeptides from <i>Onychocola sclerotica</i>
Three new cyclic tetrapeptides (<b>1</b>ā<b>3</b>) have been isolated from the crude fermentation extract
of <i>Onychocola sclerotica</i>. The planar structures of <b>1</b>ā<b>3</b> were elucidated by detailed spectroscopic
analyses using one- and two-dimensional NMR experiments and high-resolution
mass spectrometry. The absolute configuration of the amino acid residues
in each cyclotetrapeptide was established by Marfeyās method.
Compounds <b>1</b>ā<b>3</b> displayed activity
as cardiac calcium channel blockers (Cav1.2) but did not inhibit the
hERG potassium channel and were not cytotoxic. These peptides are
the first secondary metabolites ever reported from fungi of the order
Arachnomycetales