In our investigation of in vitro anti-allergic screening of medicinal herbal extracts, the ethyl acetate extract of the root of Wikstroemia indica was observed to inhibit nitric oxide (NO) production in a lipopolysaccharide (LPS) and recombinant mouse interferon-γ (IFN-γ) activated murine macrophage-like cell line, RAW 264.7. Fractionation of the active extract led to the isolation of two new lignan dimer bis-5,5-nortrachelogenin (1) and bis-5,5′-nortrachelogenin (2), and three known lignans. Compound 1 and lirioresinol B (5) inhibited NO production with IC₅₀ values at 48.6 and 53.5 μM, respectively. Compound 5 also showed free radical scavenging effect on 1,1-diphenyl-2-picrylhydrazil (DPPH) at IC₅₀ values at 19.5 μM.