It has long been known that mushrooms contain unique physiologically active substances. However, in practice, it is not easy to identify useful bioactive substances. At Tottori University, we are constructing a mushroom extract library centered on rotting fungi. In the process, our laboratory succeeded in isolating an unprecedented level of highly active tyrosinase inhibitor from Matsuouji (Scientific Name: Neolentinus lepideus), and we also determined the structure of this mushroom. We welcome consultations from cosmetics companies that are interested in this compound, as well as companies that are interested in exploring, developing, and commercializing new physiologically active substances using the Tottori University's Mushroom Extract Library. Melanin is a substance that is produced in the skin and causes spots and freckles in addition to being a pigment for hair. Therefore, one of the important issues in whitening cosmetics is how much melanin production can be suppressed. Melanin is known to be biosynthesized from “tyrosine”, an amino acid, as a starting material via L-dopa and dopaquinone. An oxidase called “tyrosinase” works in the process of converting tyrosine to L-dopa and L-dopa to dopaquinone. Tyrosinase inhibitors such as arbutin and hydroquinone are often used in whitening cosmetics because it is possible to suppress the production of melanin by inhibiting the action of tyrosinase. Hydroquinone is structurally similar to tyrosine and L-dopa and competitively binds to tyrosinase with its natural substrate, thereby inhibiting tyrosinase from acting on tyrosine and L-dopa. This is called “competitive inhibition”. Arbutin is also a glycoside of hydroquinone and acts as a tyrosinase inhibitor as well. Tottori University has a lot of mushroom strains at the Fungus/Mushroom Resource and Research Center (FMRC), and in order to make effective use of them, regarding mushrooms such as natural fruiting bodies and cultured fruiting bodies and mycelium culture solutions, etc. Mushroom Extract Library is under construction. Mushroom extracts selected from this Mushroom Extract Library were tested for tyrosinase inhibitory activity. After adding the mushroom extract to the solution containing L-dopa, add tyrosinase and observe the color (absorbance) after the reaction. When tyrosinase works effectively, dopaquinone (and dopachrome) is produced, so the activity of tyrosinase can be measured by measuring the absorbance at its absorption peak. Absorbance at 475 nm is lower when tyrosinase is inhibited. As a result of doing this for several kinds of mushroom extracts, it was confirmed that Matsuoji has particularly high tyrosinase inhibitory activity. Moreover, we have identified two compounds as active ingredients (tyrosinase inhibitors) in Matsuouji. We have applied for patents on these two compounds. It has been confirmed that the tyrosinase inhibitory activity of these compounds has an order of magnitude lower IC50 value (in other words, higher activity) than the known hydroquinone and arbutin. In this way, it is no exaggeration to say that the tyrosinase inhibitors identified and confirmed by our laboratory are epoch-making, exhibit extremely high inhibitory activity, and are expected to be used as whitening ingredients in whitening cosmetics.