Photoisomerization of TransResveratrol

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Photoisomerization of Trans-Resveratrol

• By Alle Taylor and Caitlin Nealon

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Trans-Resveratrol

• Compound found naturally in grapes and nuts
• Phenolic antioxidant
• High concentration in Japanese Knotweed
• Thought to slow age-related deterioration and
  functional decline
• Cardiovascular Function

http//upload.wikimedia.org/wikipedia/commons/a/a7
/Fallopia_japonica_MdE_2.jpg
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Photochemistry Photoisomerization

• Photochemistry is involved in important
  biochemical processes
• Photosynthesis
• Photochemical Reaction
• Reactant ? Reactant ? Product
• Photoisomerization Interconversion between
  isomers by photoexcitiation
• Diabatic Process The products are dictated by
  the interactions of two potential energy surfaces

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Experimental

• A 120µM solution of Trans-Resveratrol prepared
• The solution was irradiated and measurements were
  taken at 3, 8, 18, 33, and 48 minutes.
• Analysis was done by UV-Vis spectroscopy and NMR
  spectroscopy
• Percent Conversion over time from the trans to
  the cis isomer was determined.

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3
Time 0 min
6
4
2
3
6
5
2
1
2
4
5
6
1
3
6
Time 3 min
4
3
4a
5a
5
1
3a
6a
2
6
1a
2a
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Table 1 Integration Values for Trans and Cis
Isomers during Irradiation
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Table 1 Integration Values for Trans and Cis
Isomers during Irradiation
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Time 33 min
3a
2a
6a
1, 1a

6
5a
2
3
4a
4
5
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UV-Vis
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Calculating Molar Absorptivity for the trans
isomer

• Equation

Atotal etransbctrans ecisbccis
At t 0 all Trans so
etrans A/bc 2.43/(1cm)(120µM) 2.0281 x 10-4
M-1cm-1
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Percent Conversion

• Using the NMR data conversion of trans to cis
  was calculated

ftrans PItrans/PItrans PIcis
PI Peak Integration
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Table 2 Calculations of Conversion
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Graph of Conversion vs. Time
Series 1 Trans Series 2 Cis
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Concentration of Cis and Trans Isomers

• From percent conversion the concentration of both
  the cis and trans isomers were determined.

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Calculation of Molar Absorptivity Coefficient of
the cis isomer

• Using conversion at t 3 the ecis was
  calculated

ecis Atrans etransbctrans/bccis 2.07
(0.0203 63.492)/56.508 0.0138µM-1cm-1
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Figure 1 Determination of Rate Constant
m -0.0619 k 0.0619
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Acknowledgments and References

• Thank you to Dr. Yousef for his help and the rest
  of the intermediate lab II class!
• National Institutes of Health, "Resveratrol Found
  to Improve Health, But Not Longevity in Aging
  Mice on Standard Diet." NIH News. Thursday, July
  3, 2008. National Institute on Aging. 5 Apr 2009