Isolation and characterization of the glycoprotein fraction with a proliferation-promoting activity on human and hamster cells in vitro from Aloe vera gel

Fractions of leaf gel from Aloe barbadensis Mill. were prepared by gel permeation using DEAE Sephadex A-25, Sepharose 6B, and Sephadex G-50 columns. These were then tested by in vitro assays for proliferation of human normal dermal and baby hamster kidney cells. The glycoprotein fraction promoted cell growth, while the neutral polysaccharide fraction did not show any growth stimulation. Moreover, the polar-colored glycoprotein fraction strongly inhibited the in vitro assays. An active glycoprotein fraction (protein 82%, carbohydrate 11%) examined on polyacrylamide gel electrophoresis (PAGE) and SDS-PAGE showed a single band. Its molecular weight was 29 kD on a Sephadex G-50 column and its isoelectric point was pH 6.8. Immunoblotting after SDS-PAGE showed that the glycoprotein was composed of two subunits (14 kD). Deglycosylation of glycoprotein (Pg21-2b fraction) by trifluoromethanesulphonic acid provided a protein band with a molecular weight of 13 kD on SDS-PAGE. The colored glycoprotein fraction was shown on SDS-PAGE to be a mixture with a molecular weight of 18 kD - 15 kD. It was later hydrolyzed with 10 % H2SO4 to produce phenolic substances.