Asian Journal
Of Traditional Medicines

Abstract: The effects of the extracts of five Rheum sp. and six anthraquinone aglycones on degranulation in antigen-induced RBL-2H3 cells were investigated by determining the β-hexosaminidase release, a marker of degranulaion, as well as the inhibitory activity of aloe-emodin on intracellular Ca2+ concentration increase in 4.5 µM Fluo 3-AM loaded cells. The results showed that the extracts of R. officinale and R. undulatum potently inhibited degranulation, with IC50 values of 49 and 39 µg/mL, respectively. Aloe-emodin showed the highest inhibitory potency (IC50: 9.7 µM), while other anthraquinone aglycones, emodin, rhein, alizarin, and 2,6-dihydroxyanthraquinone as well as physcion, showed only moderate or weak potency. The structure-activity relationships of the tested anthraquinone aglycones on the inhibition of degranualtion in RBL-2H3 cells were analyzed as well. Further studies indicated that aloe-emodin dose-dependently inhibited the [Ca2+]i increase stimulated by antigen, with an IC50 value of 38 µM 8 min after antigen stimulation. These findings suggest that R. officinale and aloe-emodin are potential anti-allergic agents.

Key words: rhubarb, anthraquinone aglycone, aloe-emodin, RBL-2H3 cell, degranulation, [Ca2+]i