| Summary: | Tyrosinase inhibitors are gaining attention due to their iitriodora exmportant role in inhibiting melanin production. Tyrosinase inhibitors are widely used in the cosmetic industries. However, some of the well-known inhibitors are reported to be harmful and can cause undesirable side effects. Thus, application of natural ingredients in formulation has garnered massive attention among consumers to promote health and safe lifestyle. Backhousia citriodora was first introduced in Malaysia by Qzen (M) Sdn. Bhd. in 2009, in the form of stem cuttings. In this study, the extract of B. citriodora was evaluated for its biological activities. 2,2-diphenyl-1-picrylhydrazyl assay of the extract exhibited good potential for further development as antioxidant agent with IC50 values of 53.94 mg/ml, compared to ascorbic acid (83.98 mg/ml) and trolox (77.59 mg/ml). In addition, the inhibitory effect of B. citriodora extract on melanogenesis was evaluated using B16F1 melanoma cell. The cytotoxicity study was carried out using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, water soluble tetrazolium salt assay and Sulforhodamine B assay. The cell viabilities treated with B. citriodora extract with concentration at 0.03125 - 0.10 % (v/v) showed no significant effect to the cell compared to the non-treated cell. This indicates that B. citriodora extract is non-cytotoxic to the cells under the experimental condition used. Melanogenesis measured in a-MSH-induced B16F1 melanoma cells revealed that by B. citriodora extract treatment at 0.0625 - 0.10 % (v/v), the secreted melanin and intracellular melanin were significantly reduced in dose dependent manner. It can be also deduced that the inhibitory effect of B. citriodora extract is stronger than kojic acid and arbutin (positive control used). Furthermore, cellular tyrosinase activity exhibited a similar profile to melanin content. These results showed that B. citriodora extract has the ability to suppress cellular melanin synthesis in B16F1 cells.
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