title: A strategy for the separation of diterpenoid isomers from the root of Aralia continentalis by countercurrent chromatography: The distribution ratio as a substitute for the partition coefficient and a three-phase solvent system.
abstract: Aralia continentalis (Araliaceae) is widely used as a medicinal plant in East Asia. Previous studies have indicated that diterpenoid isomers (kaurenoic acid, continentalic acid, and ent-continentalic acid) are the major bioactive compounds of this plant. A new strategy was developed to alleviate difficulties in the separation of these isomers from this plant. A three-phase solvent system was applied to separate the isomers, and furthermore, the distribution ratio (Kc) was introduced as a substitute for the partition coefficient (KD). For compounds exhibiting a single equilibrium, their distributions in two immiscible phases were only affected by the partition coefficient of each solute. However, compounds that have a dissociating functional group (e.g., -COOH) are involved in two types of equilibrium in the two-phase system. In this case, the partitioning behaviors of the solutes are greatly affected by the pH of the solution. A mathematical prediction was applied for adjusting the solutions to the proper pH values. To prevent non-used phase (medium phase) waste, both the stationary phase (upper phase) and mobile phase (lower phase) were prepared on-demand without pre-saturation with the application of (1)H NMR. Each fraction obtained was collected and dried, yielding the following diterpenoid isomers from the 50mg injected sample: kaurenoic acid (19.7mg, yield: 39%) and ent-continentalic acid (21.3mg, yield: 42%).
authors.affiliation: College of Pharmacy, Natural Products Research Institute, Seoul National University, Seoul, 151-742, South Korea.
authors.forename: Kyoung Jin
authors.initials: KJ
authors.lastname: Lee
authors.affiliation: College of Pharmacy, Natural Products Research Institute, Seoul National University, Seoul, 151-742, South Korea.
authors.forename: Kwang Ho
authors.initials: KH
authors.lastname: Song
authors.affiliation: College of Pharmacy, Natural Products Research Institute, Seoul National University, Seoul, 151-742, South Korea.
authors.forename: Wonmin
authors.initials: W
authors.lastname: Choi
authors.affiliation: College of Pharmacy, Natural Products Research Institute, Seoul National University, Seoul, 151-742, South Korea. Electronic address: kims@snu.ac.k.
authors.forename: Yeong Shik
authors.initials: YS
authors.lastname: Kim
mesh_terms: D027983:Aralia / Q000737:chemistry*; D002623:Chemistry Techniques, Analytical / Q000295:instrumentation / Q000379:methods*; D003377:Countercurrent Distribution; D004224:Diterpenes / Q000302:isolation & purification; D010936:Plant Extracts / Q000032:analysis / Q000302:isolation & purification*; D018517:Plant Roots / Q000737:chemistry*; D010946:Plants, Medicinal / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry
chemical_list: D004224:Diterpenes; D010936:Plant Extracts; D012997:Solvents; C510689:continentalic acid; C051436:kaurenoic acid
keywords: Aralia continentalis; Countercurrent chromatography; Distribution ratio; Diterpenoid; Three-phase solvent system