Background and objectives: Dracocephalum species are mentioned in Iranian traditional medicine for enhancement of cognitive performance. In the present study, the acetyl cholinesterase inhibitory and butyryl cholinesterase inhibitory activities as well as the anti-oxidant and anti-tyrosinase effects of three Iranian Dracocephalum species (D. kotschyi,...

In the present paper, we report the synthesis and pharmacological evaluation of a new series of azo compounds with different groups (1-naphthol, 2-naphthol, and N,N-dimethylaniline) and trifluoromethoxy and fluoro substituents in the scaffold. All synthesized compounds (5a-5f) showed the most potent mushroom tyrosinase inhibition (IC₅₀ values in the range of 4.39 ± 0.76-1.71 ± 0.49 µM), compara...

tyrosinase has been recognized as a major autoantign in human vitiligo. here we have shown that experimental autoimmune vitiligo can be induced by intradermal injection of mushroom tyrosinase emulsified in complete freund’s adjuvant in c57bl/6 mice. the onse of vitiligo was characterized by hair hypopigmentation and total melanocyte depletion in the basal layer of the epidermis. our results con...

A series of phosphonic analogues of tyrosine and 3,4-dihydroxyphenylalanine (dopa) were synthesized in order to study their interaction with mushroom tyrosinase. 1-Amino-2-(3,4-dihydroxyphenyl)ethylphosphonic acid and 1-amino-2-(3,4-dimethoxyphenyl)ethylphosphonic acid turned out to be substrates for mushroom tyrosinase with Km values of 3.3 mM and 9.3 mM respectively. Shortening of the alkyl c...

Tyrosinase, which usually catalyzes the conversion of o-diphenols to o-benzoquinones, catalyzed an unusual oxidative dimerization of 1,2-dehydro-N-acetyldopamine to a benzodioxan derivative. The identity of the product was confirmed by UV, IR spectra, and NMR studies. During the oxidation, generation of a transient reactive intermediate could be witnessed by its characteristic visible absorptio...

In searching for tyrosinase inhibitors from plants using L-3,4-dihydroxyphenylalanine (L-DOPA) as a substrate, quercetin was found to be partially oxidized to the corresponding o-quinone under catalysis by mushroom tyrosinase (EC 1.14.18.1). Simultaneously, L-DOPA was also oxidized to dopaquinone and both o-quinones were further oxidized, respectively. The remaining quercetin partially formed a...

The tyrosinase inhibitory activity of methanol extracts of the leaves of 39 plant species growing on the seashore of Iriomote island (Okinawa, Japan) was investigated. The extracts of Hibiscus tiliaceus, Carex pumila, and Garcinia subelliptica showed potent activity among them. The inhibitors in the extract of Garcinia subelliptica were purified by assay-guided fractionation to give two biflavo...