Under the sea: An unusual antibiotic iodinated compoundChristine Jasmin*, Serge Lavoie*, David Brumley‡, and Julia Kubanek‡,*

*School of Biological Sciences, ‡ School of Chemistry and Biochemistry, Aquatic Chemical Ecology Center, Georgia Institute of Technology, Atlanta, 30332

• In 70-95% of developing countries, traditional medicines are still used for primary care.1

• Bacteria are developing more antibiotic resistance and as a result pose a threat to humans.2

• Marine plant products provide a particular interest, due to the plethora of biodiversity available.

• Marine natural products provide a varied source of halogenated metabolites, particularly in marine macro- and microalgae.3

• Through the investigation of a species of Fijian red algae, Callophycus serratus, the bioactive compound, diiodocallophycoic acid was found.4

• Scale up the isolation of diiodocallophycoic acid• Investigate its possible activity against microbes such as

methicillin-resistant Staphylococcus aureus (MRSA)• Finalize the stereochemical characterization of the compound.

Methods and Materials

Results

Name

Antibacterial MIC

(μg/mL)

MRSA VREF

Bromophycoic acid A 1.6 6.3

Bromophycoic acid B 25 >50

Bromophycoic acid C 6.3 >50

Bromophycoic acid D 12.5 >50

Bromophycoic acid E 6.3 1.6

Bromophycolide A 3.9 3.9

Bromophycolide B 3.9 2.0

Callophycoic acid G 1.6 3.1

Callophycoic acid A >50 0.8

Diiodocallophycoic acid 0.6 NT

1. Robinson, M. M.; Zhang, X.WHO 2011.2. Levy, S.B.; Marshall, B. Nat. Med. 2004, 10, S122-S129.3. Kladi, M.; Vagias, C.; Vassilios, R. Phytochem. Rev. 2004,

3, 337-366.4. Brumley, D. Fijian Macroalgae: A continued source of

novel natural products, 2014.5. Teasdale, M. E.; Shearer, T. L.; Engel, S.; Alexander, T. S.;

Fairchild, C. R.; Prudhomme, J.; Torres, M.; Le Roch, K.; Aalbersberg, W.; Hay, M. E.; Kubanek, J. J. Org. Chem. 2012, 77 (18), 8000–8006.

Acknowledgements

The Kubanek Lab• Ms. Kristy Syhapanha

The ACE REU Program• Dr. Frank Stewart• Dr. Brian Hammer• Dr. Linda Green• Dr. Claire Dell

Introduction

Conclusions

References

Diiodocallophycoic Acid’s Bioactivity

*NT= Not tested

The algae, collection G-0807 from Vitu Levi, Fiji, was extracted in methanol and dichloromethane.5 Through serial fractionations, guided by liquid chromatography mass spectrometry (LCMS) and nuclear magnetic resonance spectroscopy (NMR), the compound (1), was isolated and purified. Using the pure compound, a bioassay was performed against MRSA.

Through 2D NMR analysis techniques used to determine the interactions between different atoms on the compound, the structure of 1 was determined. Using this backbone, along with information from circular dichroism and polarimetry, the 3D structure of the compound was finalized.

• While being structurally similar to previously discovered callophycoic acids, diiodocallophycoicacid uniquely contains iodine atoms

• Diiodocallophycoic acid is a potent antibiotic against MRSA

• Discovery of diiodocallophycoic adds to the wealth of knowledge of compounds derived from natural products with medicinal properties

• High resolution mass of the deprotonated molecular ion was 816.888 g.• Compound (1) showed an optical rotation of -56°(c=0.082 in CHCl3).• Known compounds (2-4) were also isolated

Extraction

Methanol andMethanol:Dichlo-romethane 1:1

Liquid-Liquid partition

Methanol/H2O, Hexanes and Dichloromethane

Solid Phase Extraction

High Performance Liquid Chromatography

0%

50%

100%

50 500 5000

MR

SA S

urv

ival

Concentration (ng/ml)

0100200300400500600700800900

1000

Rel

ativ

e co

nce

ntr

atio

n o

f 1

Fractions

LCMS guides future fractionation Hexane

DCM

MeOH/H O

50%

75%

80%

85%

90%

95%

100%

Solid Phase Extraction % Methanol

International Cooperative Biodiversity Groups

Other Compounds Isolated Alongside 1

Objective

Chemical Shifts (ppm)

2

Liquid-Liquid Partition

NMR verifies purity and provides structural insight

1 is the most potent against MRSA in comparison to other compounds isolated from this genus

Dose Response Curve shows a minimum inhibitory concentration of 0.6 µg/mL against MRSA