11 research outputs found
R06. Identification of the Cellular Pathways Targeted by Two Antifungal Natural Products Using RNA-Seq Analysis
Corresponding author (NCNPR): Ameeta Agarwal, [email protected]://egrove.olemiss.edu/pharm_annual_posters/1005/thumbnail.jp
Synthesis of Natural Acylphloroglucinol-Based Antifungal Compounds against <i>Cryptococcus</i> Species
Thirty-three natural-product-based
acylphloroglucinol derivatives
were synthesized to identify antifungal compounds against <i>Cryptococcus</i> spp. that cause the life-threatening disseminated
cryptococcosis. In vitro antifungal testing showed that 17 compounds
were active against <i>C. neoformans</i> ATCC 90113, <i>C. neoformans</i> H99, and <i>C. gattii</i> ATCC 32609,
with minimum inhibitory concentrations (MICs) in the range 1.0–16.7
μg/mL. Analysis of the structure and antifungal activity of
these compounds indicated that the 2,4-diacyl- and 2-acyl-4-alkylphloroglucinols
were more active than <i>O</i>-alkyl-acylphloroglucinols.
The most promising compound found was 2-methyl-1-(2,4,6-trihydroxy-3-(4-isopropylbenzyl)phenyl)propan-1-one
(<b>11j</b>), which exhibited potent antifungal activity (MICs,
1.5–2.1 μg/mL) and low cytotoxicity against the mammalian
Vero and LLC-PK1 cell lines (IC<sub>50</sub> values >50 μg/mL).
This compound may serve as a template for further synthesis of new
analogues with improved antifungal activity. The findings of the present
work may contribute to future antifungal discovery toward pharmaceutical
development of new treatments for cryptococcosis
Chloramphenicol Derivatives with Antibacterial Activity Identified by Functional Metagenomics
A functional metagenomic approach identified novel and diverse soil-derived DNAs encoding inhibitors to methicillin-resistant Staphylococcus aureus (MRSA). A metagenomic DNA soil library containing 19 200 recombinant Escherichia coli BAC clones with 100 Kb average insert size was screened for antibiotic activity. Twenty-seven clones inhibited MRSA, seven of which were found by LC-MS to possess modified chloramphenicol (Cm) derivatives, including three new compounds whose structures were established as 1-acetyl-3-propanoylchloramphenicol, 1-acety1-3-butanoyl-chloramphenicol, and 3-butanoyl-1-propanoylchloramphenicol. Cm was used as the selectable antibiotic for cloning, suggesting that heterologously expressed enzymes resulted in derivatization of Cm into new chemical entities with biological activity. An esterase was found to be responsible for the enzymatic regeneration of Cm, and the gene trfA responsible for plasmid copy induction was found to be responsible for inducing antibacterial activity in some clones. Six additional acylchloramphenicols were synthesized for structure and antibacterial activity relationship studies, with 1-p-nitrobenzoylchloramphenicol the most active against Mycobacterium intracellulare and Mycobacterium tuberculosis, with MICs of 12.5 and 50.0 mu g/mL, respectively.Identification of anti-microbial agents from metagenomic clone
Antibacterial Prenylated Acylphloroglucinols from <i>Psorothamnus fremontii</i>
Psorothatins A–C (<b>1</b>–<b>3</b>),
three antibacterial prenylated acylphloroglucinol derivatives, were
isolated from the native American plant <i>Psorothamnus fremontii</i>. They feature an unusual α,β-epoxyketone functionality
and a β-hydroxy-α,β-unsaturated ketone structural
moiety. The latter forms a pseudo-six-membered heterocyclic ring due
to strong intramolecular hydrogen bonding, as indicated by the long-range
proton–carbon correlations in the NMR experiments. Psorothatin
C (<b>3</b>) was the most active compound against methicillin-resistant <i>Staphylococcus aureus</i> and vancomycin-resistant <i>Enterococcus
faecium</i>, with IC<sub>50</sub> values in the range 1.4–8.8
μg/mL. The first total synthesis of <b>3</b> described
herein permits future access to structural analogues with potentially
improved antibacterial activities
Bacillusin A, an Antibacterial Macrodiolide from <i>Bacillus amyloliquefaciens</i> AP183
Bioassay-guided fractionation of
the organic extracts of a <i>Bacillus amyloliquefaciens</i> strain (AP183) led to the discovery
of a new macrocyclic polyene antibiotic, bacillusin A (<b>1</b>). Its structure was assigned by interpretation of NMR and MS spectroscopic
data as a novel macrodiolide composed of dimeric 4-hydroxy-2-methoxy-6-alkenylbenzoic
acid lactones with conjugated pentaene-hexahydroxy polyketide chains.
Compound <b>1</b> showed potent antibacterial activities against
methicillin-resistant <i>Staphylococcus aureus</i> and vancomycin-resistant <i>Enterococcus faecium</i> with minimum inhibitory concentrations
in a range of 0.6 to 1.2 μg/mL. The biosynthetic significance
of this unique class of antibiotic compounds is briefly discussed
LC-MS- and <sup>1</sup>H NMR Spectroscopy-Guided Identification of Antifungal Diterpenoids from <i>Sagittaria latifolia</i>
Antifungal screening of small-molecule
natural product libraries
showed that a column fraction (CF) derived from the plant extract
of <i>Sagittaria latifolia</i> was active against the fungal
pathogen <i>Cryptococcus neoformans</i>. Dereplication analysis
by liquid chromatography–mass spectrometry (LC-MS) and proton
nuclear magnetic resonance spectroscopy (<sup>1</sup>H NMR) indicated
the presence of new compounds in this CF. Subsequent fractionation
of the plant extract resulted in the identification of two new isopimaradiene-type
diterpenoids, <b>1</b> and <b>2</b>. The structures of <b>1</b> and <b>2</b> were determined by chemical methods and
spectroscopic analysis as isopimara-7,15-dien-19-ol 19-<i>O</i>-α-l-arabinofuranoside and isopimara-7,15-dien-19-ol
19-<i>O</i>-α-l-(5′-acetoxy)arabinofuranoside,
respectively. Compound <b>1</b> exhibited IC<sub>50</sub> values
of 3.7 and 1.8 μg/mL, respectively, against <i>C. neoformans
and C. gattii</i>. Its aglycone, isopimara-7,15-dien-19-ol (<b>3</b>), resulting from acid hydrolysis of <b>1</b>, was
also active against the two fungal pathogens, with IC<sub>50</sub> values of 9.2 and 6.8 μg/mL, respectively. This study demonstrates
that utilization of the combined LC-MS and <sup>1</sup>H NMR analytical
tools is an improved chemical screening approach for hit prioritization
in natural product drug discovery
Biological evaluation of phytoconstituents from <i>Polygonum hydropiper</i>
<p>Fourteen compounds including vanicoside B (<b>1</b>), vanicoside F (<b>2</b>), vanicoside E (<b>3</b>) and 5,6-dehydrokawain (<b>4</b>), aniba-dimer-A (<b>5</b>), 6,6′-((1<i>α</i>,2<i>α</i>,3<i>β</i>,4<i>β</i>)-2,4-diphenylcyclobutane-1,3-diyl)bis(4-methoxy-2<i>H</i>-pyran-2-one) (<b>6</b>), (+)-ketopinoresinol (<b>7</b>), isorhamnetin (<b>8</b>), 3,7-dihydroxy-5,6-dimethoxy-flavone (<b>9</b>), isalpinin (<b>10</b>), cardamomin (<b>11</b>), pinosylvin (<b>12</b>), 2-desoxy-4-<i>epi</i>-pulchellin (<b>13</b>) and <i>β</i>-sitosterol (<b>14</b>) were isolated from dichloromethane-soluble portion of <i>Polygonum hydropiper</i>. By using Alamar blue assay, compounds <b>2</b>, <b>7</b>, <b>8</b>, <b>11</b> and <b>12</b> were found to be active against <i>Trypanosoma brucei</i> with IC<sub>50</sub> values in the range of 0.49–7.77 μg/mL. Cardamomin (<b>11</b>) had most significant activity against <i>T. brucei</i> with IC<sub>50</sub>/IC<sub>90</sub> values of 0.49/0.81 μg/mL compared to the positive control DFMO (IC<sub>50</sub>/IC<sub>90</sub>: 3.02/8.05 μg/mL). Furthermore, in antimalarial, antimicrobial, anti-inflammatory, PPAR and cytotoxic assays, some compounds have demonstrated moderate inhibitory potentials.</p
UPLC-MS-ELSD-PDA as a Powerful Dereplication Tool to Facilitate Compound Identification from Small-Molecule Natural Product Libraries
The generation of natural product
libraries containing column fractions,
each with only a few small molecules, using a high-throughput, automated
fractionation system, has made it possible to implement an improved
dereplication strategy for selection and prioritization of leads in
a natural product discovery program. Analysis of databased UPLC-MS-ELSD-PDA
information of three leads from a biological screen employing the
ependymoma cell line EphB2-EPD generated details on the possible structures
of active compounds present. The procedure allows the rapid identification
of known compounds and guides the isolation of unknown compounds of
interest. Three previously known flavanone-type compounds, homoeriodictyol
(<b>1</b>), hesperetin (<b>2</b>), and sterubin (<b>3</b>), were identified in a selected fraction derived from the
leaves of <i>Eriodictyon angustifolium</i>. The lignan compound
deoxypodophyllotoxin (<b>8</b>) was confirmed to be an active
constituent in two lead fractions derived from the bark and leaves
of <i>Thuja occidentalis</i>. In addition, two new but inactive
labdane-type diterpenoids with an uncommon triol side chain were also
identified as coexisting with deoxypodophyllotoxin in a lead fraction
from the bark of <i>T. occidentalis.</i> Both diterpenoids
were isolated in acetylated form, and their structures were determined
as 14<i>S</i>,15-diacetoxy-13<i>R</i>-hydroxylabd-8(17)-en-19-oic
acid (<b>9</b>) and 14<i>R</i>,15-diacetoxy-13<i>S</i>-hydroxylabd-8(17)-en-19-oic acid (<b>10</b>), respectively,
by spectroscopic data interpretation and X-ray crystallography. This
work demonstrates that a UPLC-MS-ELSD-PDA database produced during
fractionation may be used as a powerful dereplication tool to facilitate
compound identification from chromatographically tractable small-molecule
natural product libraries