# Ultrasound-Assisted Extraction of \(\beta\)-Asarone from Sweet Flag (_Acorus calamus_) [PERSON]
## 3 Results and Discussions
### The Kinetics of Ultrasonic-Assisted Extraction of \(A\). calamus
However, caution needs to be exercised for heated conventional extraction as \(\beta\)-asarone is known to be volatile. The extraction yields of (Yt) Increase substantially when sonication power was applied for all experiments. The largest increase (2.5-fold) was observed in the 30% sonication power to 1:100 solid-to-solvent ratio experiment. This shows the advantages of applying sonication in the extraction process. The results in Table 1 showed a slight increase in extract yield (Yt) (30% and 50% ultrasound power) in the solid-to-solvent ratio 1:100 experiment when compared to that of the 1:50 experiment, indicating the dominant effect of a higher concentration gradient due to lower solid-to-solvent ratio [37]. However, at 70% ultrasound power, the higher solid-to-sample ratio experiment (1:50) gave a higher extraction yield, indicating the favorable application of ultrasound-assisted extraction in a higher solid-to-solvent ratio. However, it was observed that the variation in ultrasound power does not exert much difference on the extraction yield. This observation proves that efficient energy processing can be achieved even at low sonication power for small-scale extraction of \(\beta\)-asarone from _A. calamus_. Using the kinetic model as represented in Equation (1), we can further analyze the effect of sonication upon the washing- and diffusion-dominance stages of extraction. It was interesting to note that for the 1:100 solid-to-solvent ratio, the rate of washing stage (k\({}_{\rm w}\)) increment was very dependent on the sonication power used. The increments were \(\sim\)1.5-fold (852/569 \(\times\) 10\({}^{-3}\)), \(\sim\)1.4-fold (816/569 \(\times\) 10\({}^{-3}\)) and \(\sim\)1.1-fold (633/569 \(\times\) 10\({}^{-3}\)) for 70%, 50% and 30% ultrasound power applied, respectively. The same trend was observed for the 1:50 solid-to-solvent ratio condition with increments of \(\sim\)1.6 (815/485 \(\times\) 10\({}^{-3}\)), \(\sim\)2.2 (1055/485 \(\times\) 10\({}^{-3}\)), and \(\sim\)1.8 (870/485 \(\times\) 10\({}^{-3}\)) for 70, 50 and 30% ultrasound power applied, respectively. Such observation implies the significant ultrasound influence on the washing stage during the extraction process. Further discussion on the physical effect of sonication on the washing mechanistic stage will be presented in the following section. A similar trend was observed for the rates of diffusion stage (k\({}_{\rm d}\)). For the 1:100 solid-to-solvent ratio, the k\({}_{\rm d}\) were found to increase by \(\sim\)1.3-fold (146/112 \(\times\) 10\({}^{-3}\)), \(\sim\)1.3-fold (142/112 \(\times\) 10\({}^{-3}\)) and \(\sim\)1.1-fold (120/112 \(\times\) 10\({}^{-3}\)) for 70, 50 and 30% ultrasound power applied, respectively. For the 1:50 solid-to-solvent ratio, the k\({}_{\rm d}\) were found to increase by \(\sim\)1.4-fold (141/100 \(\times\) 10\({}^{-3}\)), \(\sim\)1.7-fold (168/100 \(\times\) 10\({}^{-3}\)), and \(\sim\)1.5-fold (148/100 \(\times\) 10\({}^{-3}\)) for 70, 50, and 30% ultrasound power applied, respectively. This could also represent the ability of ultrasound to positively influence the diffusion process.