# Optimizing Nigella Oil Extraction Temperature for Sustainable Production
## 3 Results and Discussion
### Thymoquinone  
The superimposed HPLC chromatograms of TQ obtained from one replicate of an oil sample screw pressed at different temperatures (40-80 \({}^{\circ}\)C) have been shown in Figure 1 as an example. Variations in TQ content in response to extraction temperature were observed \begin{table}
\begin{tabular}{c c c c} \hline
**Oil Extraction** & **TPC** & **FRAP** & **CUPRAC** \\
**Temperature** & **(mg GAE/100 g)** & **(mg TE/100 g)** & **(mg TE/100 g)** \\ \hline Extraction at 40 \({}^{\circ}\)C & 90.4 \(\pm\) 7.7 a & 414.9 \(\pm\) 27.2 a & 411.4 \(\pm\) 19.5 a \\ Extraction at 50 \({}^{\circ}\)C & 89.4 \(\pm\) 5.0 a & 409.1 \(\pm\) 17.3 a & 380.4 \(\pm\) 28.4 a \\ Extraction at 60 \({}^{\circ}\)C & 89.9 \(\pm\) 8.9 a & 493.9 \(\pm\) 46.6 b & 410.3 \(\pm\) 19.4 a \\ Extraction at 70 \({}^{\circ}\)C & 85.8 \(\pm\) 8.5 a & 422.1 \(\pm\) 31.2 a & 391.8 \(\pm\) 38.7 a \\ Extraction at 80 \({}^{\circ}\)C & 81.1 \(\pm\) 2.0 a & 389.0 \(\pm\) 6.7 a & 417.0 \(\pm\) 39.6 a \\ \hline \end{tabular} Values \(\pm\) SD (\(n=5\)) with different letters along the column are statistically different (\(p<0.05\)).  
\end{table} 
Table 2: Chemical characteristics in Nigella oil extracted with screw press machine at different temperatures. in the present study, with concentrations ranging between 1027.4 and 1244.7 mg/100 g (Table 3). The lowest value of TQ was observed when extraction was conducted at 80 \({}^{\circ}\)C, while the higher value was found at 50 \({}^{\circ}\)C.  
Notably, the total TQ content in oil extracted at 50 \({}^{\circ}\)C showed no significant difference to that at 40 \({}^{\circ}\)C (1228.2 mg/100 g) and 60 \({}^{\circ}\)C (1171.7 mg/100 g). This sensitivity of TQ to temperature variations has been well-reported in the literature [18; 60; 61]. [PERSON] et al. [60] and [PERSON] et al. [62] reported that TQ has a melting point between 49 and 50 \({}^{\circ}\)C and starts decomposing at 65 \({}^{\circ}\)C, with complete degradation occurring around 213 \({}^{\circ}\)C. Given its medicinal importance, the stability of TQ has been extensively investigated by many researchers [27; 28; 63]. [PERSON] et al. and [PERSON] et al. [28] observed significant degradation of TQ under acidic, basic, oxidation, and UV light conditions. For example, [PERSON] et al. [28] noted rapid degradation under light exposure, regardless of pH and solvent type. Additionally, [PERSON] and [PERSON] [63] reported that prolonged light exposure leads to the gradual conversion of TQ to dithymoquinone (70-80%), which further undergoes redox reactions to give other degradation products. Optimizing extraction temperature to achieve maximum concentration of important phytoconstituents, such as TQ, without compromising the oil yield is crucial from a sustainability perspective. Since the present study observed the direct proportion and inverse proportion of oil yield and TQ, respectively, with the extraction temperature, balancing these factors is essential for sustainable production. By optimizing extraction processes to maintain high TQ content while maximizing oil yield, we can ensure efficient resource utilization and minimize waste. Furthermore, TQ has been widely recognized for its potent antioxidant properties by many researchers [64; 65; 66]. However, the present findings contrast with these reports. Despite the highest and the lowest values of TQ being observed in oils extracted at 40 \({}^{\circ}\)C and 80 \({}^{\circ}\)C, respectively, the present study found that the TPC and antioxidant capacity were  
Figure 1: HPLC chromatogram of Nigella oil extract (oil screw pressed at 40–80 \({}^{\circ}\)C).