## 4 Conclusions  
The simplex-centroid mixture design was found to be the best design for this study, and it was successfully developed for the evaluation of mixtures from different leaf extracts of the Melastomataceae family species in the formulation of the highest antioxidant activity. By using the desirability function, the optimal formulation obtained for each _Melastoma_ extract composed of _M. malabathricum_, _M. hirta_, and _M. decemfidum_ was found to be in the ratio of 3:4:3 mixtures, respectively. In addition, the present study also showed that each _Melastoma_ leaf extract contained a significant bioactive antioxidant compound of rutin and quercetin through the HPLC method. The in vitro anti-collagenase and anti-elastase activity of optimum _Melastoma_ extract exhibited good inhibition activity of more than 70% against both elastase and collagenase enzymes. There could be clear alternatives for the utilization of _Melastoma_ plant mixtures for formulations in the cosmetics industry to overcome and prevent various degenerative diseases, especially aging.  
[PERSON] participated in the design of the study and performed the experiments and statistical analysis. [PERSON], [PERSON], and [PERSON] were involved in the design of the study, supervised the experimental workflow, and helped draft the manuscript. [PERSON] participated in the sequence alignment and drafted the manuscript. All authors read and approved the final manuscript.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample** & **R2** & \
\begin{tabular}{c} **Remaining Elastase** \\ **Activity (\%)** \\ \end{tabular} &
\begin{tabular}{c} **Inhibition of Elastase** \\ **Activity (\%)** \\ \end{tabular} \\ \hline Mixture of _Melastoma_ extract & 0.9508 & 27.78 & 72.22 \\ Inhibitor (elastastinal) & 0.9644 & 27.22 & 72.23 \\ Negative (control) & 0.9881 & 100.00 & 0.00 \\ \hline \hline \end{tabular}
\end{table}
Table 8: Inhibition elastase activity of a mixture of _Melastoma_ leaf extracts.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample** & **R2** & \
\begin{tabular}{c} **Remaining Elastase** \\ **Activity (\%)** \\ \end{tabular} &
\begin{tabular}{c} **Inhibition of Elastase** \\ **Activity (\%)** \\ \end{tabular} \\ \hline Mixture of _Melastoma_ extract & 0.9891 & 29.13 & 70.78 \\ Inhibitor (collagenase) & 0.9829 & 20.43 & 79.57 \\ Negative (control) & 0.9649 & 100.00 & 0.00 \\ \hline \hline \end{tabular}
\end{table}
Table 9: Inhibition collagenase activity of a mixture of _Melastoma_ leaf extracts.  
Figure 7: The percentage of remaining elastase and collagenase activity for a mixture of _Melastoma_ extracts.  
**Funding:** This work was financially supported by the Fundamental Research Grant Scheme (FRGS) under the Ministry of Higher Education, Malaysia (grant number: 5540164), within the project title \"The Antioxidants and Functional Cosmeceuticals Properties of Leaves Melastomataceae Family Species and Its Potential for Stratum Corneum Applications.\"  
**Acknowledgments:** The authors would like to acknowledge the Laboratory of Halal Science Research, Halal Products Research Institute, Universiti Putra Malaysia (UPM), for consultation and expert advice to complete the research work.  
**Conflicts of Interest:** The authors declare that there are no conflict of interest regarding the publication of this paper.