Nitrite Measurement and Cell Viability Assay. The methods
were essentially the same as reported previously.20 To assess the effects
on LPS-induced NO production, compounds 15 (purity >98% as
checked by their 1H NMR), the two positive controls aminoguanidine
(a specific inhibitor of iNOS) and Nω-nitro-L-arginine (L-NNA, a
nonselective NOS inhibitor), or vehicle (0.1%, DMSO) was added in
the presence of LPS (200 ng/mL) to the RAW 264.7 cells. Both
inhibitors were purchased from Sigma-Aldrich Chemical Co., and the
purity of each compound was more than 98%. The nitrite concentration
in the culture medium was determined spectrophotometrically as an
index of NO production. The Alamar Blue assay was used to examine
whether the amount of the test specimens used in this study caused cell
damage. Results are expressed as percentage of inhibition calculated
versus vehicle plus LPS-treated cells.