Technical Abstract: Bioassay-guided isolation and purification of the ethyl acetate extract of Moringa oleifera fruits yielded three new phenolic glycosides; 4-[(2'-O-acetyl-a-L-rhamnosyloxy) benzyl]isothiocyanate (1), 4-[(3'-O-acetyl-a-L-rhamnosyloxy)benzyl]isothiocyanate (2), and S-methyl-N-{4-[(a-L-rhamnosyloxy)benzyl]}thiocarbamate (3), together with five known phenolic glycosides (4–8). The structures of the new metabolites were determined on the basis of spectroscopic analyses including 1D- and 2D-NMR and mass spectrometry. The anti-inflammatory activity of isolated compounds was investigated with the lipopolysaccharide (LPS)–induced murine macrophage RAW 264.7 cell line. It was found that 4-[(2'-O-acetyl-a-L-rhamnosyloxy)benzyl]isothiocyanate (1) possessed potent NO–inhibitory activity with an IC50 value of 1.67 µM, followed by 2 (IC50 = 2.66 µM), 4 (IC50 = 2.71 µM), and 5 (IC50 = 14.4 µM), respectively. Western blots demonstrated these compounds reduced LPS-mediated iNOS expression. In the concentration range of the IC50 values, no significant cytotoxicity was noted. Structure–activity relationships following NO-release indicated: (1) the isothiocyanate group was essential for activity, (2) acetylation of the isothiocyanate derivatives at C-2' led to higher activity, and (3) acetylation of the thiocarbamate derivatives reduced activity. These data indicate compounds 1, 2, 4 and 5 are responsible for the reported NO–inhibitory effect of Moringa oleifera fruits, and further studies are warranted.