Chapter 17 Naturally Occurring OxygenContaining Compounds

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Chapter 17Naturally Occurring Oxygen-Containing
Compounds

• Spring 2009
• Terry Bunde

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Lipids

• Neutral Lipids
• Fats and Oils Triacylglycerols
• Waxes Fatty alcohol-Fatty acid esters
• Sterols cholesterol
• Fatty Acid Esters FAME
• Terpenes isoprene derivatives

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Lipids

• Polar Lipids
• Phosphatidic Acid - PA
• Phosphatidyl Choline - PC
• Phosphatidyl Ethanolamine PE
• Phosphatidyl Serine PS
• Phopshatidyl Inositol PI
• Phosphatidyl Glycerol PG
• Cardiolipin

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Phospholipids
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Lysophospholipids
Hydrolysis catalyzed by phospholipase B
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Triacylglycerols

• Triesters of glycerol (propane-1,2,3-triol) and
  long chain carboxylic acids (also called fatty
  acids)
• Alkyl chains have one, two, or more double bonds
  in cis configuration, methylene interrupted
  double bonds non conjugated
• Exist as liquids or semisolids or solids
  depending upon chain length and the number of
  double bonds in the side chains

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Fatty Acids

• Caproic acid (C60)
• Caprylic acid (C80)
• Capric acid (C100)
• Lauric acid (C120)
• Myristic acid (C140)
• Palmitic acid (C160)
• Stearic acid (C180)
• Oleic acid (C181) (?9, ?9)
• Linoleic acid (C182) (?9,12, ?6)
• Linolenic acid (C183) (?9,12,15, ?3)

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Reactions of Triacylglycerols

• Saponification
• Base catlyzed hydrolysis of the three esters to
  form glycerol and three sodium salts of the fatty
  acids (also called soaps)
• Transesterification (FAME) (FAEE)
• Base or acid catalyzed conversion of the fatty
  acid groups to methyl or ethyl esters and glycerol

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Transesterification Reagents

• Sodium hydroxide and methanol sodium methoxide
• HCl or H2SO4 and methanol with heating
• BF3 (10-20) in methanol

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Biodiesel SynthesisTransesterification
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Biodiesel Preparation

• Prepare sodium methoxide by combining sodium
  hydroxide and methanol with stirring
• Heat vegetable oil to 40 degrees C
• Combine methoxide and fat and stir for 20-60
  minutes
• Separate the upper FAME layer in a separatory
  funnel or by centrifugation

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Biodiesel Continued

• Remove upper layer (biodiesel) and run the
  following tests
• FT-IR by placing one drop between two NaCl
  windows in a beta cell
• H-NMR by running the sample (0.8 mL) neat with
  10 TMS
• Refractive Index of the FAME fraction
• GC separation of FAME

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FT-IR
T
Wavenumber cm-1
Biodiesel, synthetic sample (neat liquid)
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H-NMR
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GC Separation
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GC FAME Composition
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GC FAME Tallow
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Biodiesel Characteristics
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Structures Formed from Amphipathic Compounds

• Soap bubbles in water
• Monolayers on water
• Micelles in water
• Bilayer membranes in water
• Bilammellar vesicles liposomes
• All driven by entropy effects which are
  collectively called hydrophobic bonding

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Amphipathic Lipids
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Singer-Nicolson Model for Membranes

• Sea of lipids in the bilayer membrane
• Proteins floating in the sea of lipids
• Proteins can span the membrane integral
  proteins
• Proteins can float in one leaflet peripheral
  proteins
• Lipids can move both within a leaflet and can
  also flip from one leaflet to the other

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Singer-Nicolson Membrane
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Cell Membrane
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Terpene Synthesis

• Terpenes called non-saponifiable lipids
• Formed from a single metabolic intermediate
  isopentyl pyrophosphate
• Condensation reactions can occur in three ways
• Head to head linkage
• Head to tail linkage
• Tail to tail linkage

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Dimerization
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Biosynthesis of Cholesterol
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HMG-CoA Pathway
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Isoprene Units in Terpenes
Terpenes are made up of isoprene units fused
either head to tail or head to head. Two units
make a monoterpenes, four make a diterpene.
Three units (C15) are called sesquiterpenes.
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Terpenes
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Terpene Derivatives
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Steroid Biosynthesis
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Steroids
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Steroid Derivatives
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Ginko Biloba TerpenesSeparated by GLC-FID
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GC-MS Separation of Citrus Oils
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Possible Separation Methods

• RP-HPLC of citrus extracts or hot pepper extracts
  using isocratic methods with 50 methanol solvent
  and UV 280nm detection
• GC separation of citrus oils using an RP-5 column
  and temperature program
• GC-MS separation of citrus oils (must be volatile
  at 200 C)
• TLC separation of capsaicin in peppers

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Bioassays Employed

• Anti-pyretic activity
• Anti-viral activity
• Anti-tumor activity
• Anti-hypertensive activity
• Anti-bacterial and fungal activity
• Analgesic activity
• Anti-inflammatory activity

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FT-IR Spectrum or Orange Peel Steam Distillation
Extract
Wavenumber cm-1
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Analysis Procedure
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Carbohydrates

• Polyhydroxy aldehydes and ketones
• Stereochemistry almost always D using the Fischer
  D/L system all based on D-glyceraldehyde
• Trioses Tetroses Pentoses Hexoses- Heptoses
  found in nature
• Form stable hemialcetals and hemiketals
• Polymerize by forming acetals and ketals

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Aldohexose Structures
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Nomenclature of Sugars
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Disaccharides
Trehalose
Cellobiose
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Leaving Groups in Metabolic Reactions

• Three kinds of esters are found in metabolic
  reactions
• Phosphate, pyrophosphate esters (pKa2)
• Sulfate esters (pKa -10)
• Carboxylate esters (pKa 5)
• Why are phosphate esters so common?
• The nucleophile can attack EITHER the phosphate
  or the carbon of the ester (p822)

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Sucrose Polyester
Olestra
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Inversion of Sucrose
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Natural Products Lab

• Spring 2009
• Chemistry 224

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Completion of the Vanillin Reduction Laboratory

• Centrifuge the fermentation mixture
• Remove the supernatent and distill to remove the
  ethanol and water. Stop when you have about five
  milliliters.
• Extract the distillation bottoms with an equal
  volume of methylene chloride
• Allow the CH2Cl2 to evaporate and collect the
  crystals
• Obtain a MP, a FT-IR, and maybe H-NMR

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Natural Products Lab

• Extract a natural product mixture from some
  source
• Alcohol tincture method
• Soxhlet extraction in ether/hexane
• Supercritical fluid extraction
• Steam distillation
• Analysis/Separation of extract
• FT-IR, HPLC, TLC, NMR. GC

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Methods of Isolation

• 1. Steam Distillation
• 2. Supercritical Fluid Extraction (CO2)
• 3. Soxhlet Extraction
• 4. Ethyl Alcohol Tinctures
• 5. Olive Oil Tinctures
• 6. Organic Solvent Extraction

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Methods for Separation

• NP-Thin Layer Chromatography
• RP-Thin Layer Chromatography
• Gas Chromatography
• High Performance Liquid Chromatography both NP,
  RP, and ion-exchange
• Liquid-Liquid Extraction
• Solid Phase Extraction

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Possible Lab Extractions

• Ethanol (95) Tincture of dried hot peppers
• Ethanol Tincture of fresh flowers and aromatic
  herbs (rosemary, fennel)
• Soxhlet Extraction (diethyl ether) of nutmeg,
  catnip, cinnamon, whole cloves
• Steam Distillation of citrus rind (orange,
  lemons, limes)
• Supercritical Fluid Extraction dry ice

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Conformation of Structure

• FT-IR of the extract looking for key functional
  groups of anticipated molecules
• FT-NMR (13-C and 1-H) of purified extract (after
  column chromatography, preparative TLC, or solid
  phase extraction)
• UV-Vis of extracted compounds looking for key
  peaks of anticipated compounds