title: Enzymatic synthesis and characterization of hydroquinone galactoside using Kluyveromyces lactis lactase.
abstract: 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 Ki value of HQ-Gal (0.75 mM) against tyrosinase was smaller than that of beta-arbutin (Ki=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.
authors.affiliation: Interdisciplinary Program of Graduate School for Bioenergy and Biomaterials, Chonnam National University, Gwangju 500-757, Republic of Korea.
authors.forename: Go-Eun
authors.initials: GE
authors.lastname: Kim
authors.forename: Jin-Ha
authors.initials: JH
authors.lastname: Lee
authors.forename: Sun-Hwa
authors.initials: SH
authors.lastname: Jung
authors.forename: Eun-Seong
authors.initials: ES
authors.lastname: Seo
authors.forename: Sheng-De
authors.initials: SD
authors.lastname: Jin
authors.forename: Ghahyun J
authors.initials: GJ
authors.lastname: Kim
authors.forename: Jaeho
authors.initials: J
authors.lastname: Cha
authors.forename: Eui-Joong
authors.initials: EJ
authors.lastname: Kim
authors.forename: Ki-Deok
authors.initials: KD
authors.lastname: Park
authors.forename: Doman
authors.initials: D
authors.lastname: Kim
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D005697:Galactosides / Q000138:chemical synthesis*; D006873:Hydroquinones / Q000138:chemical synthesis* / Q000737:chemistry; D007716:Kluyveromyces / Q000201:enzymology*; D043322:Lactase / Q000378:metabolism*; D051379:Mice; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D005697:Galactosides; D006873:Hydroquinones; D043322:Lactase