Journal
JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
Volume 58, Issue 17, Pages 9492-9497Publisher
AMER CHEMICAL SOC
DOI: 10.1021/jf101748j
Keywords
Kluyveromyces lactis; lactase; hydroquinone; acceptor reaction; galactosylation; DPPH assay; Tyrosinase inhibition; MTT assay
Funding
- Korea government (MEST) [2009-0090(125)]
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Hydroquinone galactoside (HQ-Gal) as a potential skin whitening agent was synthesized by the reaction of lactase (beta-galactosidase) from Kluyveromyces lactis, Aspergillus oryzae, Bacillus circulans, and Thermus sp. with lactose as a donor and HQ as an acceptor. Among these lactases, the acceptor reaction involving HQ and lactose with K. lactis lactase showed a higher conversion ratio to HQ-Gal (60.27%). HQ-Gal was purified using butanol partitioning and silica gel column chromatography. The structure of the purified HQ-Gal was determined by nuclear magnetic resonance, and the ionic product was observed at m/z 295 (C12H16O7Na)(+) using matrix assisted laser desorption ionization time-of-flight mass spectrometry. HQ-Gal was identified as 4-hydroxyphenyl-beta-D-galactopyranoside. The optimum conditions for HQ-Gal synthesis by K. lactis determined using response surface methodology were 50 mM HQ, 60 mM lactose, and 20 U mL(-1) lactase. These conditions produced a yield of 2.01 g L-1 HQ-Gal. The half maximal inhibitory concentration (IC50) of diphenylpicrylhydrazyl scavenging activity was 3.31 mM, indicating a similar antioxidant activity compared to beta-arbutin (IC50 = 3.95 mM). The K-i value of HQ-Gal (0.75 mM) against tyrosinase was smaller than that of beta-arbutin (K-i = 1.97 mM), indicating its superiority as an inhibitor. HQ-Gal inhibited (23%) melanin synthesis without being significantly toxic to the cells, while beta-arbutin exhibited only 8% reduction of melanin synthesis in B16 melanoma cells compared with the control. These results indicate that HQ-Gal may be a suitable functional component in the cosmetics industry.
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