Objective: Our country contains a large number of medical and aromatic plants with rich flora. Nowadays phytotherapy research has become popular. The purpose of this study was to evaluate the antioxidant and antimicrobial capacities, and tyrosinase inhibitory effect of methanolic extracts of Dactylorhiza osmanica.

Material and Method: The antioxidant properties of extract were investigated using in vitro antioxidant assay methods such as total phenolic content (TPC), ferric reducing antioxidant power (FRAP), and the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity assay. Enzyme inhibitory effect was tested aganist tyrosinase. The phenolic composition of extract was investigated by means of reverse phase-high performance liquid chromatography (RP-HPLC). Antimicrobial activity was tested using the disc diffusion method. Tyrosinase inhibitor activity was tested to colorimetrically.

Results: The total phenolic content value is 11.2 ± 0.472 mg gallic acid per gram sample, FRAP value is 240 ± 2.645 μM Trolox/g sample, and IC₅₀ value for DPPH assay has been found as 0.708 ± 0.010 mg/mL. Phenolic compounds were identified as gallic acid, proto-catechuic acid, proto-catechuic aldehyde, p-hydroxy benzoic acid, chlorogenic acid, caffeic acid, vanillin, p-coumaric acid, syringaldehyde, ferulic acid, and benzoic acid. The IC50 value of the extract was not significant in determining tyrosinase inhibitor activity. The extract displayed moderate antibacterial activity against an acid-fast bacterium (M. smegmatis), some Gram pozitive (S. aureus and B. cereus) and Gram negatif (Y. pseudotuberculosis) bacteria.

Conclusion: According to the results of the present study, D. osmanica can be considered as a potential source for developing new pharmaceuticals.