ArgTX-636, a polyamine isolated from spider venom: A novel class of melanogenesis inhibitors.

To discover new molecules with an inhibitory activity of melanogenesis a hundred of scorpions, snakes, spiders and amphibians venoms were screened for their capacity to inhibit mushroom tyrosinase using 3,4-l-dihydroxyphenylalanine (l-DOPA) as substrate. The Argiope lobata spider venom proved to be the most active. HPLC fraction containing Argiotoxine-636 (ArgTX-636), a polyamine known for its numerous biological activities, was found to also show a good regulation activity of melanogenesis by inhibiting DOPA and 5,6-dihydroxyindole-2-carboxylic acid (DHICA) oxidases activities, wore by tyrosinase (TYR) and tyrosinase-related protein 1 (TRP-1), respectively. Our results demonstrate that ArgTX-636 reduced the mushroom tyrosinase activity in a dose-dependent way with a maximal half inhibitory concentration (IC