Purified Compounds from Phyllanthus amarus Schum. & Thonn. Inhibit Mast Cell Degranulation via Modulation of Syk/PLCγ Signaling

Phyllanthus amarus has long been used in traditional medicine and contains diverse bioactive compounds with potential pharmacological properties. This study aimed to purify the compounds from P. amarus and investigate their inhibitory effects on mast cell degranulation in vitro. It was found that the ethyl acetate fraction from P. amarus possesses potential inhibitory effects on mast cell degranulation. Subsequently, three compounds, including 3,3′,4-tri-O-methylellagic acid (P1), ethyl brevifolincarboxylate (P2), and 4′,4′′′-di-O-methyl cupressuflavone (P3), were purified and identified. These compounds significantly inhibited mast cell degranulation via decreasing histamine release and IL-4 and TNF-α production from the activated mast cells without any cytotoxicity. Furthermore, Western blot analysis confirmed that these compounds suppressed phosphorylation of Syk and PLCγ, suggesting inhibition of the degranulation-related signaling cascade. These findings provide preliminary in vitro evidence that purified constituents from P. amarus may inhibit mast cell degranulation, potentially in association with modulation of Syk/PLCγ signaling, and support further mechanistic and in vivo investigations.