## 2 Results
### Antioxidant Activity  
The analysis of the antioxidant results revealed that CD showed potential for preserving antioxidant constituents in _S. crispus_ despite the long dying duration of 150-180 min. Samples dried using CD at 40 \({}^{\circ}\)C (2,2'-azinobis(3-ethylbenzthiazole-6-sulfonic acid) (ABTS): 5.08, and ferric-reducing antioxidant power (FRAP): 5.98 \(\upmu\)M Trolox/100 g dry weight (dw)), and CD at 60 \({}^{\circ}\)C (ABTS: 4.67, and FRAP: 5.67 \(\upmu\)M Trolox/100 g dw) achieved the highest antioxidant values that were significantly higher than those of FD (ABTS: 3.57, and FRAP: 4.48 \(\upmu\)M Trolox/100 g dw). The long exposure to heat and oxygen did not reduce the antioxidant activity. In previous studies, antioxidant activities and polyphenol contents in heat-treated peppermint, oregano, _Artemisia annua_, and various Lamiaceae herbs, such as rosemary, marjoram, oregano, sage, thyme, and basil [10, 11], increased, indicating that phenolic compounds at a partial state of oxidation are exposed to oxygen and may show a high antioxidant activity. CPD-VMFD (50 \({}^{\circ}\)C, 9 W/g) and CD at 50 \({}^{\circ}\)C produced the lowest ABTS, FRAP, and total phenolic content (TPC). A good agreement between these values is shown in Table 1. We assumed that degradative enzymes in _S. cripus_ could achieve optimum activity at 50 \({}^{\circ}\)C. Therefore, phenolic and antioxidant compounds were likely degraded. Both drying methods which operated at the same temperature of 50 \({}^{\circ}\)C consistently yielded samples with low antioxidant activities and TPC values. It was observed that the FRAP values of fresh samples were lower than those of some dried samples. Thermal treatment in drying may have caused an easier release of cell constituents from plant cells [12]. This is because heat is known to exert modifications to the microstructure of plant cells, thereby reducing plant cell integrity [13]. This allows for the easy exit of antioxidants from plant cells to the extraction solvent. This is in agreement with past studies which reported that dried \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Drying** & \multicolumn{2}{c}{**Antioxidant Activity (\(\upmu\)M Trolox/100 g dw)**} & \multicolumn{2}{c}{**Total Phenolic Content**} \\ \cline{2-4}
**Method** & **ABTS** & **FRAP** & **(mg/100 g dw)** \\ \hline Fresh & 6.10 \(\pm\) 0.56 a & 4.96 \(\pm\) 0.31 a & 1222.33 \(\pm\) 75.87 a \\ FD & 3.57 \(\pm\) 0.37 b & 4.48 \(\pm\) 0.20 a,c & 873.63 \(\pm\) 13.86 b \\ VMD 6 W/g & 3.97 \(\pm\) 0.07 b,c & 4.85 \(\pm\) 0.07 a & 898.88 \(\pm\) 16.56 b \\ VMD 9 W/g & 4.47 \(\pm\) 0.21 c,e & 5.61 \(\pm\) 0.34 b & 904.05 \(\pm\) 41.90 b \\ VMD 12 W/g & 3.46 \(\pm\) 0.35 b & 3.88 \(\pm\) 0.09 c & 830.37 \(\pm\) 21.28 b,c \\ CPD-VMFD & 2.65 \(\pm\) 0.23 d & 3.09 \(\pm\) 0.32 d & 734.45 \(\pm\) 47.93 c,e \\ CD, 40 \({}^{\circ}\)C & 5.08 \(\pm\) 0.10 e & 5.98 \(\pm\) 0.21 b & 1051.32 \(\pm\) 25.36 d \\ CD, 50 \({}^{\circ}\)C & 2.55 \(\pm\) 0.00 d & 2.99 \(\pm\) 0.17 d & 675.23 \(\pm\) 12.02 e \\ CD, 60 \({}^{\circ}\)C & 4.67 \(\pm\) 0.17 c,e & 5.67 \(\pm\) 0.10 b & 1086.71 \(\pm\) 46.76 d \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Effect of drying methods and parameters on the antioxidant activity and total phenolic content (TPC) of _Strobulanthes crispus_ leaves. leaves have the tendency to show increased bioactivity [14; 15]. Furthermore, loss of moisture that occurs in leaves during drying, which is categorized as abiotic stress, may have caused the formation and accumulation of phenolic compounds, thereby increasing the overall antioxidant activity [16]. Additionally, the increase in antioxidant activity in dried leaves compared to fresh leaves may be the result of Maillard reaction, producing Maillard reaction products (MRPs), with antioxidant power [17]. Table 1 also shows the TPC of fresh and dried _S. crispus_. The TPC value obtained from the fresh sample was 1222 mg/100 g dw, comparable with the TPC value of 1262 mg/100 g dw described in a previous study [2].