## 3 Results and Discussion
### Melanin Content Assay and Tyrosine Activity  
The biosynthesis of melanin plays an important role in the pigmentation of the skin [41]. Vitiligo is a disease caused by depigmentation of cells in the epidermis and decreased melanin biosynthesis in skin epidermal cells, a complex process regulated by tyrosinase  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sample** & **Sample Concentration** & **Sample** & **C. albicans** & _E. coli_ & _S. aureus_ \\  & **(\(\upmu\)g/mL)** & **Amount (\(\upmu\)L)** & **(mm ZOI)** & **(mm ZOI)** & **(mm ZOI)** \\ \hline Ampicillin & 4.88 & 20 & NT & 12.5 & 10 \\ Amphoterican B & 5 & 20 & 15 & NT & NT \\ _B. haynesii_ XJB-5 & 50 & 20 & 11.5 & 15 & 14 \\ _B. proteolyticxis_ XJB-16 & 50 & 20 & 11 & NA & 16 \\ _B. haltolerans_ XJB-35 & 50 & 20 & 10.5 & 17.5 & 18 \\ _B. safensis_ XJB-71 & 50 & 20 & 8.5 & 12.5 & 14 \\ _P. mutagenesis_ XJB-7 & 50 & 20 & 12 & 10 & 16 \\ _L. fastiformis_ XJB-17 & 50 & 20 & 10 & NA & 16 \\ _S. Intelists_ XJB-66 & 50 & 20 & 9.5 & 15 & 17 \\ _L. alexenkovybala_ XJB-12 & 50 & 20 & 10.5 & 8.5 & 18 \\ _P. alvei_ XJB-14 & 50 & 20 & 14 & 13 & 14 \\ _P. aggglomerans_ XJB-62 & 50 & 20 & 11 & 11 & 12 \\ \hline \hline \end{tabular}  
NA—not active; NT—not tested.  
\end{table}
Table 3: In vitro antimicrobial activity (zone of inhibition) of crude extracts of endophytic bacteria from the medicinal plant _V. anthelmintica_.  
enzymes [42]. Many natural products isolated from the medicinal plant _V. anthelmintica_ have been used for the treatment of pigmentation disorders [43,44]. Previous studies have reported that crude extracts and pure natural compounds obtained from endophytic microorganisms of _V. anthelmintica_ are involved in the regulation of melanin synthesis and tyrosinase activity [19,45]. In the present study, we investigated the influence of secondary metabolites produced by endophytic bacteria in the stem of _V. anthelmintica_. Our results showed that crude extracts of only six endophytic bacteria, _B. halotolerans_ XJB-35, _B. haynesii_ XJB-5, _B. proteolytic_ XJB-16, _L. fusiformis_ XJB-17, _L. adecarboxylylata_ XJB-12, and _P. agglomerans_ XJB-62, demonstrated increased melanin synthesis (226.1 \(\pm\) 16.57%, 197.5 \(\pm\) 18.65%, 168.3 \(\pm\) 17.5%, 164.5 \(\pm\) 15.68%, 152.7 \(\pm\) 7.989%, and 145.6 \(\pm\) 7.373%, respectively) in murine B16 cell, at a concentration of 50 uM, compared with the positive control 8-MOP (129.9 \(\pm\) 4.179%). According to the testing data (Figure 3A and Table 4), only four bacterial endophytes exhibited stronger increased melanin synthesis and tyrosinase activity at different concentrations compared to the positive control (8-MOP 50 uM, 129.9 \(\pm\) 4.179%). Therefore, we treated them again with various concentrations. The crude extract of _B. halotolerans_ XJB-35 exhibited powerful melanin synthesis inhibition with 14g/mL, 138.6 \(\pm\) 7.638%; 10 ug/mL, 161.5 \(\pm\) 3.751%; and 50 ug/mL, 229.9 \(\pm\) 6.737% concentrations, respectively. The endophytic bacteria _B. haynesii_ XJB-5 (1 ug/mL, 185.6 \(\pm\) 12.51%; 10 ug/mL, 191.5 \(\pm\) 76.61%; and 50 ug/mL, 198.2 \(\pm\) 18.65%) (Figure 4), _L. fusiformis_ XJB-17 (1 ug/mL, 129.3 \(\pm\) 10.02%; 10 ug/mL, 139.8 \(\pm\) 1.822%; 50 ug/mL, 183.8 \(\pm\) 7.762%), and _B. proteolytic_ XJB-16 (1 ug/mL, 118.8 \(\pm\) 11.50%; 10 ug/mL, 138.1 \(\pm\) 7.450%; 50 ug/mL, 179.0 \(\pm\) 2.288%) increased melanin synthesis by up to 1.5 fold compared with 8-MOP (50 uM, 132.0 \(\pm\) 2.818%) (Figure 3B and Table 5) depending on the concentration. Four selected bacterial strains also increased tyrosinase activity as well as melanin synthesis in a dose-dependent manner (Figure 3C). All results were compared with the positive control 8-MOP (50 uM, 124.1 \(\pm\) 3.172%).