Inhibitory effects of adlay bran (Coix lachryma-jobi L. var. ma-yuen Stapf) on chemical mediator release and cytokine production in rat basophilic leukemia cells.

BACKGROUND

Adlay (Job's tears, Coix lachryma-jobi L. var. ma-yuen Stapf) has long been used in China to treat rheumatism.

OBJECTIVE

We investigated the anti-allergic effects of adlay bran on rat basophilic leukemia (RBL)-2H3 cells.

METHODS

To evaluate the anti-allergic effects of adlay bran, the release of histamines and cytokines were measured using ELISA. To explore the mechanism of these effects, the protein expression levels were determined using western blotting.

RESULTS

A 40.8μg/mL concentration of the ethyl acetate fraction of the ethanolic extracts of adlay bran (ABE-EtOAc) effectively inhibited mast cell degranulation. The 40-100% EtOAc/Hex subfractions of ABE-EtOAc inhibited histamine release with an IC(50) of 71-87μg/mL. Moreover, the ABE-EtOAc subfractions suppressed the secretion of interleukin (IL)-4, IL-6 and tumor necrosis factor-α in the RBL-2H3 cells, indicating that adlay bran can inhibit cytokine secretion in the late phase of the allergic reaction. In addition, adlay bran reduced the intracellular production of reactive oxygen species, inhibited the phosphorylation of Akt and decreased the expression of protein kinase C. Furthermore, six phenolic acids and one flavone were isolated. Of these compounds, luteolin showed the most potent inhibitory activity (IC(50)=1.5μg/mL).

CONCLUSIONS

Adlay bran extract reduced the release of histamines and cytokines and suppressed the production of Akt. These combined effects influenced the signal transduction in RBL-2H3 cells, thereby revealing the mechanisms of the anti-allergic effects of adlay.