Objective To investigate the effects of friedelin (terpenoid) and 8-hydroxyisocapnolactone-2-3-diol (coumarin) with concentration 10 μM, 30 μM, and 100 μM on inhibiting mast cells (MCs) degranulation. Methods The investigation was performed in vitro by administering each compound into rat peritoneal MCs and rat basophilic leukemia-2H3 cells followed by activation with 50 μg/mL of compound 48/80 or 1 μM of ionomycin. The concentration of histamine released from each group was measured by a high-performance liquid chromatography-fluorometry system with post-column derivatization using o-phthalaldehyde. Results 8-Hydroxyisocapnolactone-2-3-diol inhibited degranulation of compound 48/80 activated-rat peritoneal MCs with the histamine release percentages of 74.57%, 72.21% and 51.79% when the 10 μM, 30 μM and 100 μM concentrations were used, respectively. Where as about 81% histamine was released by the control group. Degranulation inhibition ability was also observed in ionomycin-activated rat basophilic leukemia-2H3 cells. In contrast, friedelin failed to inhibit degranulation in either cell type. The inhibition of 8-hydroxyisocapnolactone-2-3-diol was not related to the depletion of histamine synthesis as implied by the total histamine measurement. Conclusions These results exhibit the promising of 8-hydroxyisocapnolactone-2-3-diol is a potential parent structure for developing a MCs stabilizer.