Anti-allergenic activity of polymethoxyflavones from Kaempferia parviflora

• The 13 polymethoxyflavones from Kaempferia parviflora suppressed antigen-induced degranulation of RBL-2H3 cells.
• 5-hydroxy-3,7,4′,-trimethoxyflavone and 5,3′-dihydroxy-3,7,4′-trimethoxyflavone had potent inhibitory effects.
• These flavones suppressed degranulation due to Ca2+ influx, phosphorylation of PLCγ1, and translocation of FcεRI.

The inhibitory effects of 13 polymethoxyflavones (PMFs) obtained from Kaempferia parviflora extracts were evaluated on RBL-2H3 cell degranulation. These flavones suppressed antigen-induced degranulation in RBL-2H3 cells. 5-Hydroxy-3,7,4′,-trimethoxyflavone (KP02) and 5,3′-dihydroxy-3,7,4′,-trimethoxyflavone (KP10) showed potent inhibitory activities. KP10 significantly suppressed calcium ionophores, such as A23187 and 2,5-ditert-butylhydroquinone, which promoted calcium influx from the outside of cells and from the endoplasmic reticulum, respectively. However, these activities did not fully explain the PMFs' effects. Immunoblot analysis of KP02 and KP10 showed that the inhibitory effects were attributable to the downregulation of PLCγ1 kinase phosphorylation in the signaling pathways involved in degranulation. The phosphorylation levels of Syk were also suppressed by the addition of KP10. KP02 and KP10 treatment to the cells did not affect the high affinity IgE receptor (FcεRI) levels inside RBL-2H3 cells, but they suppressed the FcεRI levels in the plasma membrane. Therefore, K. parviflora PMFs have multiple degranulation mechanisms to suppress RBL-2H3 cells and would be beneficial for alleviating type I allergy symptoms.