• YAKHAK HOEJI
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• v.45 no.2
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• pp.214-219
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• 2001

Nineteen hydrolysable tannins isolated from the Euphorbia helioscopia (Euphorbiaceae) were tested for the inhibitory effect on mushroom tyrosinase activity in vitro. Inhibitory effect of gallotannin group exhibited more potent than that of phenolcarboxylic acid and ellagitannin groups against the enzyme activity. The inhibitory activity by pentagalloyl glucose on mushroom tyrosinase was more potent ($IC_{50}$/, 4.9 $\mu$M) than that of kojic acid ($IC_{50}$/, 8.7 $\mu$M).

• Journal of Life Science
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• v.16 no.3 s.76
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• pp.396-399
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• 2006

Crude extract prepared from sweet potato possessed inhibitory activity toward mushroom tyrosinase. The inhibitory activity was dependent upon the addition amount of sweet potato extract. After heating the sweet potato extract at $95^{\circ}C$ for 20 min, its inhibitory activity retained 37.3%. Its optimum activity was shown at pH ranges of 5.0-7.0. The tyrosinase inhibitory activity was disappeared by dialysis, which suggests the inhibitory activity of sweet potato extract is caused by some compounds of low molecular weight.

• Korean Journal of Pharmacognosy
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• v.35 no.4 s.139
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• pp.380-383
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• 2004

The purpose of this study was to evaluate mushroom Tyrosinase inhibitory activity of Cuscuta japonica Choisy and C. australis R.Be. The experimental materials were expressed juice from their stems and flowers, both water and ethanol extracts, their seeds, and two kinds of commercially available cosmetic packing Wontosa and Bupjetosa (made from seeds of C. japonica). The 50% inhibitory concentration $(IC_{50})$ of C. Japonica juice was 5.4 mg/ml. However, C. australis juice showed negligible mushroom tyrosinase inhibitory activity. The $IC_{50}$ of water extracted C. japonica seed was $54.0\;{\mu}g/ml$, water extracted product of Wontosa $50.0\;{\mu}g/ml$ and Bupjetosa $40\;{\mu}g/ml$. The $IC_{50}$ of ethanol extracted C. japonica seed was $10\;{\mu}g/ml$, Wontosa $10\;{\mu}g/ml$ and Bupjetosa $20\;{\mu}g/ml$.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.23 no.3
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• pp.115-121
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• 1997

To identify inhibitors of melanogenesis, we compared the effects of 5 compounds on mushroom tyrosinase, human melanocytic tyrosinase activity and melanin content. The cytotoxicyty of the components were also tested on cultured human melanoctes. Kojic acid showed marked inhibitory effect both on mushroom and human tyrosinase activity. This action of kijic acid is stronger than that of ascorbic acid. Arbutin inhibited human tyrosinase activity of cultured melanocytes although it had slightly inhibitory effect on mushroom tyrosinase activity. Azelaic acid had no effect on human tyrosinase activity. Melanin production was inhibited significantly by kojic acid and tranexamic acid. MTT assay showed that all of the compounds were non-cytotoxic to melanocytes at the concentrations tested. These results suggest that the effect of kojic acid on cultured meanocytes involve inhibition of tyrosinase activity and melanogenesis without affection the cell number.

• Korean Journal of Korean Medical Institute of Dermatology and Aesthetics
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• v.1 no.1
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• pp.91-97
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• 2005

(1) Objectives: To discover natural skin-lightening agents, we have evaluated the inhibitory activity of EtOH extracts from 20 medicinal plants against mushroom tyrosinase. (2) Methods: Tyrosinase activity was determined by the dopachrome method using L-tyrosine as the substrates. (3) Results: Of the plant extracts tested, the extracts of 4 plants, Albizzia julibrissin, Curcuma longa, Anethum graveolens and Sophora flavescens, exhibited potent inhibitory activity (> 50%) in mushroom tyrosinase assay. Four plant extract, extracts of Agrimonia pilosa, Paeonia moutan, Magnolia obovata and Eugenia caryophyllata also showed relatively strong inhibitory (> 40%) against mushroom tyrosinase. (4) Conclusion: These active medicinal plants may be useful for the development of skin-whitening agents. Since the active medicinal plants may contain effective tyrosinase inhibitors even more than kojic acid, further study to identify the active constituents from the plants is expected.

• Journal of Microbiology and Biotechnology
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• v.16 no.12
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• pp.1977-1983
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• 2006

Kaempferol was isolated and identified from the methanol extract of the flowers of Impatiens balsamina. Kaempferol showed inhibitory activity against mushroom tyrosinase with an $ID_{50}$ of 0.042 mM. Inhibition kinetics, as determined using a Lineweaver-Burk plot, showed kaempferol to be a competitive inhibitor of mushroom tyrosinase with a $K_i$ value of 0.011 mM. The lag phase of tyrosine hydroxylation catalyzed by mushroom tyrosinase clearly increased on increasing the concentration of kaempferol. In addition to its tyrosinase inhibiting activity, kaempferol strongly inhibited melanin production by Streptomyces bikiniensis, in a dose-dependent manner, without inhibiting cell growth. For comparative purposes, the tyrosinase inhibitory activity of kaempferol was also assayed versus quercetin, a positive standard.

• YAKHAK HOEJI
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• v.45 no.5
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• pp.522-528
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• 2001

Tyrosinase plays an important role in the process of melanin biosynthesis, and it is a biochemical target enzyme for skin-whitening agents and the remedy for disturbances in pigmentation. We have screened 25 natural plant extracts for inhibitory effects against DOPA oxidase activity of tyrosinase. For the inhibitory effect against DOPA oxidase activity of tyrosinase, the recombinant human tyrosinase and the purified mushroom tyrosinase were used. Each of the dried plants extracted with methanol, and then the extracts were subjected to sequential fractionations with methylene chloride, ethyl acetate, n-butanol and water, respective The methylene chloride fractions of Angelica tenuissima, Nardostachys chinensis, Bombyx mop and Saposhnikovia divaricata, and the n-butanol fraction of Bombyx mori notably inhibited the human tyrosinase activity as well as mushroom tyrosinase activity (more than 90% inhibition). This study suggests that the above extracts have a potential as whitening agents as single ingredients or in combination with other of the extracts.

• YAKHAK HOEJI
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• v.42 no.4
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• pp.353-358
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• 1998

The MeOH extract of the bark of Paeonia moutan showed potent inhibitory effect on the mushroom tyrosinase activity in vitro. The activity-guided fractionation of t he MeOH extract resulted in the isolation of three active compounds. The chemical structures of these compounds were elucidated by chemical and spectroscopic evidence as catechin, 1,2,3,6-tetra-O-galloyl-${\beta}$-D-glucose and 1,2,3,4,6-penta-0-galloyl-${\beta}$-D-glucose, respectively. Among them, the inhibitory activity by 1,2,3,6-tetra-galloyl-${\beta}$-D-glucose on mushroom tyrosinase was more potent $(IC_{50}=3.5\;{\mu}M)$ than that of kojic acid $(IC_{50}=8.7\;{\mu}M)$ ,but catechin enhanced the mushroom tyrosinase activity 50% in the concentration of 34.5M.

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.151.2-151.2
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• 2003

For the purpose of the development of a skin-whitening agent, Sophora flavescens was evaluated for tyrosinase inhibitory activity and its active principles were identified followed activity-guided isolation. The ethanol extract and dichloromethane fraction from S. flavescens showed significant inhibition of mushroom tyrosinase. From the dichloromethane fraction, three known prenylated flavonoids, sophoraflavanone G, kuraridin, and kurarinone, were isolated. Compared with kojic acid ($IC_50$=20.5 $\mu$M), these compounds possessed more potent tyrosinase inhibitory activity. (omitted)

• Korean Journal of Pharmacognosy
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• v.30 no.4
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• pp.397-403
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• 1999

Tyrosinase plays an important role in the process of melanin polymer biosynthesis. Therefore, the enzyme inhibitors have been of great concern as cosmetics to have skin-whitening effects on the local hyperpigmentation. During the search for new inhibitory compounds on melanin polymer biosynthesis from natural sources, MeOH extracts of 589 higher plants were tested for the inhibitory effect on tyrosinase activity by the muschroom tyrosinase assay in vitro. Among plants tested, the leaves of Cercis chinensis exhibited potent inhibitory effect on mushroom tyrosinase activity. Subsequently seven active compounds were isolated from the ethyl acetate soluble part of acetone extract of the leaves of C. chinensis by the activity guided fractionation monitoring the inhibitory effect on tyrosinase activity. Their chemical structures were identified as $kaempferol-3-0-{\alpha}-L-rhamnoside$, quercitrin, $myricetin-3-0-{\alpha}-L-rhamnoside$, myricetin-3-0-(2'-O-galloyl)- ${\alpha}$ -L-rhamopyranoside (desmanthin), (-)-epicatechin-3-0-gallate, (-)-epigallocatechin-3-0-gallate, and methyl gallate on the basis of the speculation of spectral data and chemical reaction. Among the flavonol rhamnosides, myricetin-3-0-(2'-O-galloyl)- -L-rhamnoside(desmanthin) showed most potent inhibitory effect on tyrosinase activity and the structure of B-ring in flavonol moiety was related to the activity. (-)-Epigallocatechin-3-O-gallate having pyrogallol group in flavan-3-ol moiety exhibited more potent inhibitory effect than (-)-epicatechin-3-0-gallate having catechol group in flavan-3-ol moiety on mushroom tyrosinase activity.