## 3 Results and Discussion
### Evaluation of Antiviral Activity of C. myrrha (T.Nees) Engl. Resin Extracts
As illustrated in Figure 5, over 50% of the virus RNA inhibition was revealed in 50 ug/mL of fumoeudesma-1,3-diene and 70 ug/mL of curzerene. Low concentrations of fumoudesma-1,3-diene (2.5-30 ug/mL) and curzerene (over 60 ug/mL) only affect up to 50% of virus inhibition [16]. The results of the present study are consistent with those of the previous studies [16]. The effects of viral RNA inhibition in the aqueous solution with the _C. myrrha_ (T.Nees) Engl. resin extracts coated with biochar were lower than those in only _C. myrrha_ (T.Nees) Engl. resin extracts. This may be attributed to the low binding concentration of terpenoids into biochar and the lower concentration of terpenoids compared with only _C. myrrha_ (T.Nees) Engl. resin extracts. These effects of viral RNA inhibition through biochar can be easily solved by increasing the amount of biochar added and enhancing terpenoid quantity binding with the activation and functionalization of  
Figure 4: Concentration of terpenoids (i.e., furanoeudesma-1,3-diene and curzerene) in solution before and after adsorption of _C. myrrha_ (T.Nees) Engl. resin extracts onto RH-BC. Conditions: 50 mg of biochar was mixed with 1 mL of the extract solution in a shaking incubator at 25 °C for 24 h at 120 rpm and dried at 60 °C for 24 h. The experiment was conducted in triplicate and the error bars represent the 95% confidence interval. A, B, C and D indicate group classified from [PERSON]’s test. The same letter means that there is no significant difference between the data. biochar. Therefore, _C. myrrha_ (T.Nees) Engl. resin extract-coated biochars (e.g., RH-BC and WD-BC) with different properties (feedstock (e.g., RH-BC; rice husk and WD-BC; and wood powder), BET surface area (i.e., RH-BC; 205.6 m\({}^{2}\)/g and WD-BC; and 211.1 m\({}^{2}\)/g), and functional groups on the surface) were evaluated for their antiviral activity (Table S1 and Figure S4). The Brunauer-Emmett-Teller (BET) surface areas of RH-BC and WD-BC were similar; however, their functional groups were different (Figure S4). Accordingly, we deduced the differences in the adsorption capacity of terpenoids onto the biochar. To confirm terpenoid binding, changes in the functional groups on the surface of the RH-BC were analyzed before and after precipitation (e.g., adsorption) using FTIR. As shown in Figure 6, 875 cm\({}^{-1}\), 1049 cm\({}^{-1}\), 1375 cm\({}^{-1}\), 1430 cm\({}^{-1}\), 1740 cm\({}^{-1}\), 2930 cm\({}^{-1}\), and 3200-3400 cm\({}^{-1}\) peaks, indicating CO\({}_{3}\)\({}^{2-}\)-, C-O stretching, C=O carboxylate ion stretching, C-H bending, C=O group, -CH group, and OH group in RH-BC and _C. myrrha_ resin extract-coated RH-BC appeared [35; 65]. Among them, the peaks at 875 cm\({}^{-1}\) and 1049 cm\({}^{-1}\), indicating CO\({}_{3}\)\({}^{2-}\)- and C-O stretching, had decreased and the peak at 1740 cm\({}^{-1}\) indicated an increase in the C=O group. Hence, these results (e.g., the increase in the C=O group) imply that the terpenoids, such as furanoeudesma-1,3-diene and curzerene, bind with the functional groups (e.g., CO\({}_{3}\)\({}^{2-}\) and C-O stretching) on the surface of RH-BC or the \(\pi\)-\(\pi\) interaction on the surface area. As shown in the XPS results, C1s, O1s, Si2s, and Si2p peaks appeared in the survey scans of the RH-BC and _C. myrrha_ (T.Nees) Engl. resin extract-coated RH-BC (Figure 7). In the comparison between RH-BC and _C. myrrha_ (T.Nees) Engl. resin extract-coated RH-BC, the C1s, O1s, Si2s, and Si2p peaks decreased after coating, indicating that various compounds in the _C. myrrha_ (T.Nees) Engl. resin extracts were bound to the surface of RH-BC. These peak intensities (e.g., C1s, O1s, Si2s, and Si2p) were similar at 25, 50, and 100 \({}^{\circ}\)C, although they slightly decreased at 200 \({}^{\circ}\)C. These phenomena can be attributed to the volatility of various compounds in the _C. myrrha_ resin extracts at high temperatures (200 \({}^{\circ}\)C).