Separation of Aloins A and B from Aloe Vera Exudates by High Speed Countercurrent Chromatography

Abstract

Aloin is the main anthraquinone in aloe leaf, which occurs naturally as a mixture of two diastereoisomers, aloin A and aloin B, and currently served as one of the important control constituents in most of the commercial aloe products. High speed countercurrent chromatography (HSCCC) has been employed for the preparative separation of individual isomers combined with preseparation on silica gel chromatography. Three solvent systems composed of chloroform‐methanol‐water (4:2:3), ethyl acetate‐methanol‐water (5:1:5), and butanol‐ethyl acetate‐water (1:3:4) have been used in HSCCC. 6 g of extract of dry aloe leaf exudates yielded 202 mg of aloin A (>98%) and 140 mg aloin B (>96%). Their structures have been confirmed by FAB‐MS and ¹HNMR through gradient enhanced nuclear overhauser effect spectroscopy (Goesy).

Keywords:

• Aloe vera
• Aloins A and B
• High speed countercurrent chromatography

Acknowledgments

The authors thank National Natural Science Foundation of China and Beijing Municipal Education Committee for financial support. We also thank Dr. X.Z. Yan of National Center of Biomedical Analysis, Academy of Military Medical Sciences (Beijing) for their FAB‐MS and NMR analysis.