Tyrosinase inhibitory and antioxidant activities of Orchid (Dendrobium spp.)

Ethanol extracts of the flowers from four Dendrobium species cultivated in Thailand including Sonia, Sonia Pink, Snow Rabbit and Shavin White were prepared using the maceration method at room temperature and their total phenolic and total flavonoid contents together with antioxidant activities using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and phosphomolybdenum assay were studied. The Shavin White extract (5.34 ± 0.30 mgGAE g− 1) showed the highest total phenolic content followed by those of Sonia and Sonia Pink, respectively whereas the Sonia Pink extract (4.01 ± 0.12 mgGAE g− 1) showed the highest total flavonoid content. The Shavin White extract also showed stronger antioxidant activities than Sonia Pink, Snow Rabbit and Sonia, respectively. All ethanolic extracts were evaluated for tyrosinase inhibitory activity using the modified dopachrome assay with L-tyrosine and L-DOPA as substrates. It was found that all extracts showed the strongest inhibition of tyrosinase in the first step (L-tyrosine) of melanin synthesis whereas they showed lower inhibitory activity in the second step (L-DOPA) of melanin synthesis. Consequently, the flowers of Dendrobium species may have dietary and medicinal applications.