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Journal of Thai Traditional & Alternative Medicine Vol. 6 No. 2 May-August (Supplement) 2008 ÒÛ˜

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Antioxidative and tyrosinase inhibition activities of extracts from

Thai Lanna medicinal plants

1,2 1 1,2
Aranya Manosroi , Pensak Jantrawut , Jiradej Manosroi
1
Faculty of Pharmacy, Chiang Mai University, Chiang Mai 50200, Thailand
2
Natural Products Research and Development Center (NPRDC), Institute for Science and Technology Research and Development,
Faculty of Pharmacy, Chiang Mai University, Chiang Mai 50200, Thailand

Principles and rationale: Thai Lanna was an independent country for over 700 years ago including 7 provinces
of the northern part in Thailand. It has its own folklore medicines, which some of them are still currently used by

the Thais. Many Thai Lanna medicinal plant recipes have shown the evidences of anti-aging.

Objective: The objective of this study was to investigate the antioxidative and tyrosinase inhibition activities of
the 15 selected Thai Lanna medicinal plants in order to get the information for the further development of anti-
aging products.

Methods: Different solvents and extraction temperatures were used to prepare the plant extracts. Antioxidative
and tyrosinase inhibition activities of the extracts were investigated by the three methods of an in vitro scavenging

assays using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, a chelating assay using the ferrous iron-ferrozine
complex and a modified dopachrome method using tyrosine as a substrate. The IC values of these assays were
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determined in comparing to the standard antioxidants, chelating agents and whitening agents.

Results: The extract prepared by an aqueous maceration with sonication of Dischidia major exhibited the highest
scavenging activity with the IC value of 0.016 ± 0.001 mg/ml in comparing to the standard antioxidants vitamin
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C, vitamin E and butylated hydroxyl toluene (BHT) which gave the IC values of 0.014 ± 0.001, 0.038 ± 0.002
50
o
and 0.049 ± 0.002 mg/ml, respectively. The Cyperus rotundus extract prepared by soxhlet extraction (70 C) and
Cassia fistula extract prepared by methanolic maceration with sonication showed the highest chelating and
tyrosinase inhibition activity with the IC values of 0.094 ± 0.001 and 0.076 ± 0.001 mg/ml in comparing to
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EDTA and kojic acid which gave the IC values of 0.079 ± 0.001 and 0.030 ± 0.001 mg/ml, respectively.
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Conclusion: The resulting three potential Thai Lanna medicinal plants, Dischidia major, Cyperus rotundus and

Cassia fistula were selected for further development of anti-aging cosmeceuticals.

Acknowledgements: Thailand Research Fund (TRF) under the RGJ-PhD program and Natural Products Research
and Development Center (NPRDC), Institute for Science and Technology Research and Development, Chiang Mai
University, Chiang Mai 50200, Thailand.