NO-releasing derivatives of OA protected hepatocytes from anti-Fas mediated apoptosis. The anti-apoptotic effects of NO-releasing derivatives of OA were evaluated by LDH assays. Briefly, HepG2 cells at 10⁴/well were plated in triplicate in 96-well plates in 4% FCS and 2 μg/ml cycloheximide in Phenol-red free DMEM. The cells were treated with anti-Fas (50 ng/ml for CH-11 or 1.5 μg/ml for DX2) in the presence or absence of indicated concentrations of OA, NCX–1000, or NO-releasing derivatives of OA at 37°C 5% CO₂ for 18 h. Unmanipulated cells or the cells treated with 1% triton X–100 were used as negative or positive controls for cytotoxicity. Their supernatants were harvested and their contained LDH activities were measured by LDH assays using the LDH cytotoxicity detection kit (Roche) and following the manufactory’s instructions at O.D. (490/650). The protective effect (%) was determined by the formula: the protective effect (%) = (1-(O.D experiments-O.D negative controls)/(O.D positive controls-O.D negative controls)) x100. Data present as the mean of three independent experiments and the O.D values of intra-group variations were less than 10%.

NO-releasing derivatives of OA produced low levels of NO in vitro. NO₂⁻ concentrations which represent the quantity of NO were determined by Griess assay. Griess reagent could combine with NO₂⁻ and form the chromophore after 10 min at 30°, the absorbance then was measured at 540nm.

Reagents and conditions: (i) Br(CH₂)_nBr, Et₃N, 50□, 4h (60–73%); (ii) AgOH, NaOH (65%); (iii) HCl ; (iv) Br(CH₂)_nBr (n=3 or 4), Et₃N, 50□, 4h (61–65%).

Reagents and conditions: (i) (CF₃CO)₂O, 2a–2g, <90°C, 6h (70–78%); (ii) THF/CH₃CN, AgNO₃, reflux (67–75%); (iii) KHCO₃, r.t. (90–95%)

Reagents and conditions: (i) (CF₃CO)₂O, 6a–6b, <90°C, 6h (71–73%); (ii) THF/CH₃CN, AgNO_3, reflux (67–73%); (iii) KHCO_3, r.t. (90–95%).