Aritalab:Lecture/Biochem/Extraction

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