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

OR-31

Free radical scavenging and tyrosinase inhibition activities of fermented

Thai rice for cosmeceuticals

1,2 1 1,2
Aranya Manosroi , Warintorn Ruksiriwanich , 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,
Chiang Mai University, Chiang Mai 50200, Thailand
*E-mail : pmpti005@chiangmai.ac.th

Rationale: Khaow Maak, is a Thai folk wisdom dessert, made from the fermented rice. The starch molecule in
the rice seeds is fermented to monosaccharide, alcohol and acid by Look Pang, a mixture of yeasts and molds. The
characteristics of the fermented rice product are acidic sweet taste and may have free radical scavenging and
tyrosinase inhibition activities.
Objective : This study has investigated the free radical scavenging and tyrosinase inhibition activities of the sap
from various varieties of rice (Oryza sativa L. var. indica) were investigated in order to evaluate their applications
in cosmeceuticals.

Methods: White plain rice, purple plain rice, brown plain rice, white glutinous rice and purple glutinous rice were
fermented with Look Pang that contained yeasts and molds for 8 days. Then, the sap was collected at initially and
everyday for 7 days. The collected sap was tested for free radical scavenging and tyrosinase inhibition activities,
using modified DPPH method and enzymatic assay of tyrosinase activity, respectively.

Result: The fermentation duration for the maximum free radical scavenging and tyrosinase inhibition activities of
the fermented glutinous rice was 3 days, whereas that of the plain rice was 6 days. Free radical scavenging activity
of sap from the fermented brown plain rice gave about 2 and 10 times higher activity than those from the purple
rice (plain and glutinous rice) and polished rice (white plain and glutinous rice), respectively. However, brown
plain rice gave about 25 and 70 times lower activity than those of the standard vitamin C and vitamin E,
respectively. Brown rice may contain higher amount of gamma-oryzanol, ferulic acid and vitamin E in the rice
brans which have anti oxidative activity than other rice. For tyrosinase inhibition activity, sap from the fermented
purple plain rice gave the highest activity, which was about 2 times higher than those of the purple glutinous rice
and brown plain rice, and about 10 times higher than that of the polished rice (white plain and glutinous rice). This
effect may be from the high contents of anthocyanin in the purple rice brans. Nevertheless, the highest tyrosinase
inhibition activity of purple plain rice was lower than the standard vitamin C and kojic acid for about 25 and 70
times, respectively. The commercial product derived from sap of the fermented Japanese rice showed 21 times
lower antioxidant activity than the Thai brown rice and 12 times lower tyrosinase inhibition activity than those of
the Thai purple plain rice, respectively.

Conclusion: This study has provided the preliminary information for the potential of sap from the fermented Thai
rice for cosmeceuticals in anti-aging application.