Aritalab:Lecture/Biochem/Extraction

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Natural product chemistry starts with

  • Extraction, and
  • Separation & Purification.

抽出

Like dissolves like

Solvent for extraction is chosen to share similar polarity with the target compound.

  • terpenoid, steroid (alicyclics and aromatics)
    → low polarity solvent (e.g. hexane)
  • saccharide, glycoside, amino acid
    → high polarity solvent (e.g. water)
  • both
    → methanol

Polarity (極性)

H2O > methanol > ethanol > acetone > ether > chloroform > benzene > cyclohexane

分離と精製

Chromatography separates target compounds using their physico-chemical difference in adsorption or partition between stationary and mobile phases.

normal phase
  • polarity of stationary phase > polarity of mobile phase
  • silica gel + organic solvent
  • cyclohexane, benzene, chloroform, ether, acetone, ethanol, methanol
reverse phase
  • polarity of stationary phase < polarity of mobile phase
  • coated silica beads + water
  • water + acetonitrile, water + methanol, water + tetrahydrofuran (THF)

(High Performance)
Liquid Chromatography
Gas Chromatography
Adsorption-type
吸着型
Liquid-solid type (LSC)

silica gel, alumina, or porous polymers are used as adsorbent.

hydrophobic:
  • polystyrene gel, polymethyl methacrylate (PMMA)
hydrophilic:
  • polyhydroxy ethylmethacrylate gel, polyvinyl alcohol gel

 Gas-solid type (GSC)

Packed column has 2∼4 mm diameter and 30∼60 cm length, and is filled with diatomite, silica and silicon oil.

Partition-type
分配型
Liquid-liquid type (LLC) uses coated-silica beads.

Hydrophobic
  • octadecylsil (ODS), phenylmethyl, dichlorophenyl, octyl
Hydrophilic
  • aminopropyl, nitrophenol, acrylamido, propylalcohol

Gas-liquid type (GLC)

Capillary column has 0.2 mm diameter and > 25 m length, whose inside part is coated with silicon oil.

シリカへの吸着度合い

-COOH > -OH > -NH2 > -C=O > -OCH3 > -Cl

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