## 2 Materials and Methods
### Synthesis of Chalcone Derivatives
\({}^{13}\)C NMR (100 MHz, CDCl\({}_{3}\)) \(\delta\): 176.63 (s, C4), 162.4 (s, C2), 155.4 (s, C9), 152.5 (s, C4\({}^{\prime}\)), 135.7 (d, C7), 133.8 (d, C2\({}^{\prime}\)), 133.5 (d, C6\({}^{\prime}\)), 133.1 (d, C5), 125.2 (s, C10), 124.6 (d, C6), 118.2 (s, C1\({}^{\prime}\)), 117.9 (d, C8), 116.7 (d, C3\({}^{\prime}\)), 103.9 (d, C3). GC-MS m/z (rel. int.) = 265.26 [M]\({}^{+}\) (10), 261.68 (1), 195.10 (2), 104.19 (10), 90.71 (9), 74.87 (11), 73.05 (100). 2-(anthracen-9-yl)-4H-chromen-4-one (**3**j**): yellow powder (yield 84%). C\({}_{23}\)H\({}_{14}\)O\({}_{2}\). Mp = 193-195 \({}^{\circ}\)C. IR (ATR diamond, cm\({}^{-1}\)) = 3063 (C-H), 1643 (C=O), 1122 (C-O) cm\({}^{-1}\). \({}^{1}\)H NMR (400 MHz, CDCl\({}_{3}\)) \(\delta\): 8.62 (s, 1H, H8\({}^{\prime}\)), 8.40 (dd, \(J_{1}\) = 7.96, \(J_{2}\) = 1.6 Hz, 1H, H5), 8.08 (dd, \(J_{1}\) = 6.7, \(J_{2}\) = 1.5 Hz, 2H, H3\({}^{\prime}\), H6\({}^{\prime}\)), 7.97 (dd, \(J_{1}\) = 7.9, \(J_{2}\) = 1.9 Hz, H10\({}^{\prime}\), H13\({}^{\prime}\)), 7.73 (ddd, \(J_{1}\) = 8.5, \(J_{2}\) = 8.6, \(J_{3}\) = 1.6 Hz, IH, H7), 7.53-7.47 (m, 6H, H6, H8, H4\({}^{\prime}\), H5\({}^{\prime}\), H11\({}^{\prime}\), H12\({}^{\prime}\)), 6.69 (s, 1H, H3). \({}^{13}\)C NMR (100 MHz, CDCl\({}_{3}\)) \(\delta\): 178.1 (s, C4), 163.8 (s, C2), 1 dilutions. An aliquot of each dilution (0.5 mL) was mixed with 0.5 mL of a methanolic solution of 1,1-diphenyl-2-picrylhydrazyl (DPPH) (7.5 mg/250 mL). The mixtures were incubated at room temperature in the dark for 30 min. Using methanol as a blank, the spectrophotometric measurement was performed at 517 nm (A\({}_{517}\)). The radical-scavenging activity was calculated as a percentage of DPPH decoloration using the following formula:  
\[\text{DPPH (\%)}=\left[1-\left(\text{B/A}\right)\right]\times 100 \tag{1}\]  
Where A represents the A value of the control (DPPH solution) and B represents the sample. All of the determinations were performed in triplicate. For each compound, the percentage of DPPH decoloration was plotted against the concentration of each dilution. The concentration that is required to decrease the absorbance of DPPH by 50% was obtained by interpolation, from a linear regression analysis, and expresses the EC\({}_{50}\) value. Quercetin was used as a reference compound. 4.2 ABTS (2-2\({}^{\prime}\)-azino-bis-(3-ethylbenzothazoline-6-sulfonate)) Radical-Scavenging Assay  
ABTS radical cation (ABTS\({}^{+}\)) scavenging assay was determined using the methodology developed by [PERSON] et al. and [PERSON] et al. (2007, 2008) with slight modifications. ABTS was dissolved in water at 7 mM concentration. ABTS radical cation (ABTS\({}^{+}\)) was produced by reacting ABTS stock solution with 2.45 mM potassium persulfate and then the mixture was kept in the dark at room temperature for 16-18 h before use. The ABTS\({}^{+}\) solution (150 \(\upmu\)L) was diluted with methanol to obtain an absorbance at 0.7 \(\pm\) 0.02, which is taken as initial absorbance. Of this solution, 980 \(\upmu\)L was added to 20 \(\upmu\)L of different concentrations of the sample. The mixture was stirred, incubated at room temperature for 30 min, and read at a wavelength of 754 nm, which was taken as the final absorbance. The results are shown as a percentage of inhibition using the following formula:  
\[\text{\% of inhibition}=\left[\left(\text{A1}-\text{A2}\right)/\text{A1} \right]\times 100 \tag{2}\]  
Where A1 is the initial absorbance of the ABTS solution and A2 is the final absorbance of the ABTS solution in the presence of the sample. All of the determinations were performed in triplicate. For each compound, the percentage of inhibition was plotted against the concentration of each dilution. The concentration required to decrease the absorbance of ABTS by 50% was obtained by interpolation, from a linear regression analysis, and expresses the EC\({}_{50}\) value. Quercetin was used as a reference compound.