## 3 Results
### In Vitro Anti-Elastase and Collagen Activity of the Mixture of Melastoma Leaf Extracts  
Human skin is a complex structure that provides various important functions, including thermoregulation and protection against harmful substances. For instance, under normal conditions, the skin produces enzymes, such as elastase and collagenase, at a normal rate through the aging process. However, overexposure to ultraviolet radiation and harmful pollution results in enzymes that are produced at a faster rate following faster degradation of elastin and collagen, which are the main basis of the extracellular matrix (ECM) of the dermis [32]. Additionally, the imbalance of ROS on the skin can interact with protein, DNA, and lipids and alter their cellular functions, thus causing premature aging and other skin-related disorders [33]. Therefore, more research is needed to determine the inhibitors of these enzymes that can be used in cosmetics and medications to protect the skin from aging.  
In this study, the in vitro inhibitory potential of bioactive compounds from the optimum mixture of _Melastoma_ extract was carried out against elastase and collagenase enzymes. Prior to the analysis, the elastase inhibitory activity was determined by inhibition of the studied sample with the neutrophil elastase enzyme, which is a purified human neutrophil elastase combined with synthetic peptides as substrate molecules. Meanwhile, the collagenase inhibitory activity was determined by inhibition of the studied sample with the MMP-1 enzyme (interstitial collagenase) combined with synthetic peptides as substrates molecules. In this study, a slope of remaining activity for the tested sample against the control (without sample) was determined and the percentage and inhibition percentage were obtained by subtracting the obtained value from 100.  
From the results in Table 8, the elastase reduction activity of the optimum mixture of _Melastoma_ extract gave a good R\({}^{2}\) (0.9508), showing that it is not significantly different between the studied sample and positive inhibitor. Based on the results, the studied sample exhibited 27.78% in remaining elastase activity when compared to the positive control (elaststinal), which was recorded to have 27.77% (Figure 7). Moreover, Table 8 also revealed that there was about 72.22% inhibition of the elastase enzyme by an optimum mixture of the _Melastoma_ extract versus the positive inhibitor, which exhibited 72.23% inhibition. Meanwhile, for collagenase inhibition activity, it can be seen that the optimum mixture of the _Melastoma_ extract exhibited 29.13% remaining collagenase activity compared to the positive inhibitor (20.43%) (Table 9, Figure 7). It also shows that there was about 70.87% inhibition of collagenase activity by an optimum mixture of the _Melastoma_ extract versus the positive inhibitor, which exhibited 79.57% inhibition. From the results, the higher percentage inhibition activity for both elastase and collagenase enzymes by optimum _Melastoma_ extract can be supported by the bioactive compounds that are present in the _Melastoma_ leaf. For instance, rutin and quercetin compounds that are found in the leaf can significantly inhibit or slow down the generation of enzymes and radical activities. Moreover, an optimum mixture of _Melastoma_ extract exhibited numerous terpenoid compounds that can increase the rate of inhibition enzyme activity, as it was previously reported that terpenoid compounds in plant extracts can act as natural inhibitor agents [32]. Therefore, it is interesting to note that the optimum mixture of the _Melastoma_ extract demonstrated good anti-elastase and anti-collagenase activity against premature skin aging.