Angewandte
Chemie
DOI: 10.1002/anie.201405990
Natural Products
Hot Paper
Forazoline A: Marine-Derived Polyketide with Antifungal In Vivo
Efficacy**
Thomas P. Wyche, Jeff S. Piotrowski, Yanpeng Hou, Doug Braun, Raamesh Deshpande,
Sean McIlwain, Irene M. Ong, Chad L. Myers, Ilia A. Guzei, William M. Westler,
David R. Andes, and Tim S. Bugni*
Abstract: Forazoline A, a novel antifungal polyketide with
in vivo efficacy against Candida albicans, was discovered using
LCMS-based metabolomics to investigate marine-invertebrate-
associated bacteria. Forazoline A had a highly unusual and
unprecedented skeleton. Acquisition of 13C–13C gCOSY and
13C–15N HMQC NMR data provided the direct carbon–carbon
and carbon–nitrogen connectivity, respectively. This approach
represents the first example of determining direct 13C–15N
connectivity for a natural product. Using yeast chemical
genomics, we propose that forazoline A operated through
a new mechanism of action with a phenotypic outcome of
disrupting membrane integrity.
The high mortality rate[2] combined with the continued rise in
fungal resistance to current therapeutics[4] demonstrates the
ever-present need for new therapeutics.
As part of a drug discovery program to discover novel
antifungal therapeutics, we analyzed a collection of marine-
invertebrate-associated bacteria using LCMS-based metab-
olomics in conjunction with disc diffusion assays. Metabolo-
mics methodology has shown great promise for streamlining
the discovery of novel natural products[5] and overcoming
historic barriers such as the high rate of rediscovery of known
compounds.[6]
Using metabolomics-based strategies which we previously
published,[5] we analyzed LCMS profiles of 34 marine-derived
bacterial extracts by principal component analysis (PCA) and
identified the strain WMMB-499, an Actinomadura sp.
cultivated from the ascidian Ecteinascidia turbinata (Herd-
man, 1880), as a metabolic outlier. After fermentation and
subsequent purification, WMMB-499 was found to produce
three distinct classes of novel compounds. The first class,
halogenated electrophilic polyketides halomadurones A–D
which activate the Nrf2-ARE pathway, was recently de-
scribed.[7] Forazoline A (1) and B (2), described herein,
represented the second novel class. The third class was
represented by a potent antibiotic, which is still under study.
Forazoline A (1) was the lead antifungal agent with a highly
unusual and unprecedented structure. Forazoline A (1)
F
ungal infections result in over 1.5 million deaths annually
worldwide and cost $12 billion to treat.[1] Candida spp. are the
most common fungal infections, especially in intensive care
units, in solid-organ transplant patients, and in blood- and
marrow-transplant patients.[2] Of the more than one hundred
known Candida spp., Candida albicans is the most common
cause of fungal-born human disease.[2] C. albicans causes
various infections, including candidiasis, which affects about
400000 people per year, with an astonishingly high mortality
rate between 46 and 75%.[2]
While amphotericin B has remained the standard for
treatment of severe systemic fungal infections, it suffers from
low solubility and is associated with dose-limiting toxicity.[3]
[*] T. P. Wyche, Dr. Y. Hou, D. Braun, Prof. Dr. T. S. Bugni
Pharmaceutical Sciences Division
J.P., I.O., and S.M. are funded by the DOE Great Lakes Bioenergy
Research Center (DOE BER Office of Science DE-FC02-07ER64494).
C.M. and R.D. are supported by grants from the National Institutes
of Health (1R01HG005084-01A1, 1R01M104975-01,
University of Wisconsin-Madison, Madison, WI 53705 (USA)
E-mail: tbugni@pharmacy.wisc.edu
R01HG005853), a grant from the National Science Foundation (DBI
0953881), and by the CIFAR Genetic Networks Program. We would
like to thank the Analytical Instrumentation Center at the University
of Wisconsin-Madison for the facilities to acquire spectroscopic
data. This study made use of the National Magnetic Resonance
Facility at Madison, which is supported by NIH grants P41RR02301
(BRTP/NCRR) and P41M66326 (NIGMS). Additional equipment
was purchased with funds from the University of Wisconsin, the
NIH (RR02781, RR08438), the NSF (DMB-8415048, OIA-9977486,
BIR-9214394), and the USDA. We would like to thank D. Demaria for
assistance with collection and Dr. R. McClain for assistance with
ICP-AES. The yeast deletion collection was kindly provided by
Charlie Boone. CD data were obtained at the University of
Wisconsin-Madison Biophysics Instrumentation Facility, which was
established with support from the University of Wisconsin and
grants BIR-9512577 (NSF) and S10RR13790 (NIH).
Dr. J. S. Piotrowski, S. McIlwain, I. M. Ong
Great Lakes Bioenergy Research Center
University of Wisconsin-Madison, Madison, WI 53726 (USA)
R. Deshpande, C. L. Myers
Department of Computer Science and Engineering, University of
Minnesota-Twin Cities, Minneapolis, MN 55455 (USA)
Dr. I. A. Guzei
Department of Chemistry, University of Wisconsin-Madison
Madison, WI 53706 (USA)
Dr. W. M. Westler
Department of Biochemistry, University of Wisconsin-Madison
Madison, WI 53706 (USA)
Prof. Dr. D. R. Andes
School of Medicine, University of Wisconsin-Madison
Madison, WI 53705 (USA)
Supporting information for this article is available on the WWW
[**] We acknowledge financial support from the University of Wisconsin-
Madison School of Pharmacy. This work was also funded by the
NIH, NIGMS Grant R01 GM092009, and in part by R01 GM104192.
Angew. Chem. Int. Ed. 2014, 53, 1 – 5
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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