and comprises six species. One of these is Amberboa ramosa JAFRI, which is an annual herbaceous plant found in India and Pakistan. The plant has tonic, aperient, febrifuge, deobstruent, cytotoxic, and antibacterial activities. Previously triterpenoids, flavanoids, steroids, and steroidal glycosides have been reported from this species. Here we report the isolation and structure elucidation of l...

OBJECTIVES Tyrosinase is a key enzyme in pigment synthesis. Overproduction of melanin in parts of the skin results in hyperpigmentation diseases. This enzyme is also responsible for the enzymatic browning in fruits and vegetables. Thus, its inhibitors are of great importance in the medical, cosmetic and agricultural fields. MATERIALS AND METHODS A series of twelve kojic acid derivatives were ...

The aim of the present study is to preliminarily investigate the antimelanogenesis effect of Inonotus obliquus extracts by cell-free mushroom tyrosinase assay. It was found that petroleum ether and n-butanol extracts might contain unknown potential tyrosinase inhibitors, while its ethyl acetate extract might contain some unknown accelerators. Six compounds were isolated and their structures wer...

The loss of tyrosinase, the key enzyme in melanin synthesis, has been implicated in the dedifferentiation of malignant melanocytes. The presence of tyrosinase transcripts and antigenic peptides in melanoma tumors prompted us to investigate whether the basis for the loss of the enzyme was proteolytic degradation. Toward this aim, we followed the kinetics of synthesis, degradation, processing, ch...

Tyrosinase is a ubiquitous enzyme with diverse physiologic roles related to pigment production. Tyrosinase inhibition has been well studied for cosmetic, medicinal, and agricultural purposes. We simulated the docking of tyrosinase and D-(-)-arabinose and found a binding energy of -4.5 kcal/mol for theup-formof D-(-)-arabinose and -4.4 kcal/mol for thedown-form of D-(-)-arabinose. The results of...

The results of the screening of thirty-one species belonging to the lichen family Graphidaceae for their ability to scavenge superoxide and inhibition of tyrosinase and xanthine oxidase activities have been presented. Graphina glaucorufa, Graphina multistriata, Graphina salacinilabiata, Graphis assamensis, Graphis nakanishiana and Phaeographopsis indica showed strong inhibition of tyrosinase an...

Tyrosinase prepared from plant, insect, and marine animal sources catalyzes the oxidation of tyrosine, dihydroxyphenylalanine (dopa), and various structurally similar compounds to darkly colored pigments (2). The enzymatic oxidation of many of the analogues of tyrosine and dopa often proceeds at a faster rate than for tyrosine and dopa themselves (2, 3). The investigation reported here was carr...

A series of quinolines, including chloroquine and quinine, were identified as potent pigmentation inhibitors through screening a compound library in murine melanocytes. Structure-activity relationship analysis indicated that 4-substituted amino groups with a tertiary amine side chain, such as chloroquine, were associated with robust inhibitory activity. In contrast to many previously identified...