Screening of Chinese herbal medicines for antityrosinase activity in a cell free system and B16 cells.
OBJECTIVE
Tyrosinase inhibitors are becoming increasingly important in controlling skin hyperpigmentation. We aimed to screen 50 extracts from traditional Chinese medicines (TCM) for tyrosinase activity-inhibiting agents.


METHODS
The 50 herbal extracts were prepared from 32 herbs and 18 TCM formulas, which are used as folk skin whiteners in China and have not been investigated for their skin-whitening mechanisms. Each herb and formula was extracted with 30% ethanol and water, respectively, and followed by column chromatography for isolating bioactive substances such as saponins, flavonoids and alkaloids for the antityrosinase activity study. Every extract was tested using the cell free mushroom tyrosinase inhibitory assay at 2 mg/ml for the single herb extracts and 1mg/ml for formula extracts. Extracts showing greater than 50% inhibition against mushroom tyrosinase activity were further examined by cellular tyrosinase assay in mouse B16 cells. The cytotoxicity in B16 cells was measured by methyl thiazolyl tetrazolium bromide (MTT) assay.


RESULTS
In the cell-free assay, 10 out of the 50 extracts demonstrated more than 50% inhibition against mushroom tyrosinase activity. These 10 extracts were further assessed by cellular tyrosinase assay, and 6 showed>50% inhibition with IC(50) values <1 mg/ml. The 6 extracts are from 3 herbs namely Ampelopsis japonica, Lindera aggregata, and Polygonatum odoratum, and 3 formulas namely Qian-wang-hong-bai-san, Qiong-yu-gao, and San-bai-tang. As compared with vitamin C, these 6 extracts showed similar or greater ratio of cell growth IC(50) to cellular tyrosinase IC(50). As compared with arbutin, extract from Ampelopsis japonica, Lindera aggregata, Qian-wang-hong-bai-san, or San-bai-tang had a similar, although extract from Polygonatum odoratum or Qiong-yu-gao had a greater, IC(50) value against murine tyrosinase activity.


CONCLUSIONS
From the screening assays we identified three Chinese medicinal herbs and three TCM formulas that have appreciable antityrosinase activity. Further studies are warranted to develop them as skin-whitening agents with convenient dosage forms or to identify active constituents from the extracts as useful leads for the development of skin whiteners.
Ye
Yan
Y
Key Laboratory of Standardization of Chinese Medicines, Ministry of Education, Institute of Chinese Materia Medica of Shanghai University of Traditional Chinese Medicine, Zhangjiang, Shanghai, China.
Chou
Gui-Xin
GX
Mu
Dan-Dan
DD
Wang
Hui
H
Chu
Jian-Hong
JH
Leung
Alexander Kai-Man
AK
Fong
Wang-fun
WF
Yu
Zhi-Ling
ZL
D000363:Agaricales / Q000201:enzymology; D000818:Animals; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004365:Drugs, Chinese Herbal / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D008516:Medicine, Chinese Traditional; D051379:Mice; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors*; D012880:Skin Pigmentation / Q000187:drug effects; D013053:Spectrophotometry
D004365:Drugs, Chinese Herbal; D004791:Enzyme Inhibitors; D014442:Monophenol Monooxygenase