Bioassay-guided investigation of the anti-inflammatory principles from the stem and root barks of Citrus medica L. var. sarcodactylis SWINGLE has led to the isolation of a new coumarin, namely citrumedin-B (1) and thirty known compounds. The anti-inflammatory components were xanthyletin (2), nordentatin (3), atalantoflavon (4) and lonchocarpol A (5) which displayed potent nitric oxide (NO)-reducing activity in microglial cells. The structure of this new compound was completely elucidated using a combination of 2D NMR techniques (correlation spectroscopy (COSY), nuclear Overhauser effect spectroscopy (NOESY), heteronuclear multiple quantum coherence (HMQC) and heteronuclear multiple bond connectivity (HMBC)) and HR-electrospray ionization (ESI)-MS analyses. The known compounds were identified by comparison of their spectroscopic and physical data with those reported in the literature. These results can be inferred from the treatment of allergic response and inflammatory properties of Citrus medica L. var. sarcodactylis SWINGLE in traditional Chinese medicine.