Synthesis and characterization of novel astragalin galactosides using β-galactosidase from Bacillus circulans

Songhee Han, Thi Thanh Hanh Nguyen, Jaewon Hur, Nahyun M. Kim, Seong Bo Kim, Kyeong Hwan Hwang, Young Hwan Moon, Choongil Kang, Byoungsang Chung, Young Min Kim, Tae Sung Kim, Jun Seong Park, Doman Kim

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)


Astragalin (kaempferol-3-O-β-D-glucopyranoside, Ast) is a kind of flavonoid known to have anti-oxidant, anti-HIV, anti-allergic, and anti-inflammatory effects. It has low solubility in water. In this study, novel astragalin galactosides (Ast-Gals) were synthesized using β-galactosidase from Bacillus circulans and reaction conditions were optimized to increase the conversion yield of astragallin. Purified Ast-Gal1 (11.6% of Ast used, w/w) and Ast-Gal2 (6.7% of Ast used, w/w) were obtained by medium pressure chromatography (MPLC) with silica C18 column and open column packed with Sephadex LH-20. The structures of Ast-Gal1 and Ast-Gal2 were identified by nuclear magnetic resonance (NMR) to be kaempferol-3-O-β-D-glucopyranosyl-(1 → 6)-β-D-galactopyranoside and kaempferol-3-O-β-D-glucopyranosyl-(1 → 6)-β-D-galactopyranosyl-(1 → 4)-β-D-galactopyranoside, respectively. The water solubility of Ast, Ast-Gal1, and Ast-Gal2 were 28.2 ± 1.2 mg/L, 38,300 ± 3.5 mg/L, and 38,800 ± 2.8 mg/L, respectively. The SC50 value (the concentration required to scavenge 50% of the ABTS[rad]+ ) of Ast, Ast-Gal1, and Ast-Gal2 were 5.1 ± 1.6 μM, 6.5 ± 0.4 μM, and 4.9 ± 1.1 μM, respectively. The IC50 values (the half maximal inhibitory concentration) of Ast, Ast-Gal1, and Ast-Gal2 against angiotensin converting enzyme (ACE) were 171.0 ± 1.2 μM, 186.0 μM, and 139.0 ± 0.2 μM, respectively.

Original languageEnglish
Pages (from-to)59-67
Number of pages9
JournalEnzyme and Microbial Technology
Publication statusPublished - 2017 Aug

Bibliographical note

Publisher Copyright:
© 2017 Elsevier Inc.


  • ACE inhibition
  • Antioxidant activity
  • Astragalin
  • Astragalin galactoside
  • β-Galactosidase

ASJC Scopus subject areas

  • Biotechnology
  • Bioengineering
  • Biochemistry
  • Applied Microbiology and Biotechnology


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