Microbial Transformation of Galangin Derivatives and Cytotoxicity Evaluation of Their Metabolites

Abstract

Galangin (1), 3-O-methylgalangin (2), and galangin flavanone (3), the major bioactive flavonoids isolated from Alpinia officinarum, were biotransformed into one novel and four known metabolites (4–8) by application of the fungal strains Mucor hiemalis and Absidia coerulea as biocatalysts. Their structures were characterized by extensive spectroscopic analyses including one- and two-dimensional nuclear magnetic resonance spectroscopy and mass spectrometry. Compounds 1–7 were evaluated for their cytotoxic activities against cancer cell lines using the MTT assay. The new compound 3-O-methylgalangin-7-O-β-D-glucopyranoside (6) exhibited the most potent cytotoxic activity against MCF-7, A375P, B16F10, B16F1, and A549 cancer cell lines with the IC50 values at 3.55–6.23 μM.

Microbial Transformation and Biological Activities of the Prenylated Aromatic Compounds from Broussonetia kazinoki

“…The corresponding proton signals at δ H 4.50 (1H) and 3.69–3.19 (6H) were observed in the 1 H NMR spectrum. All of these data were consistent with previous reports on the d -glucose moiety [ 19 , 24 , 25 ], and the glucose was determined to be in a β-configuration by the large coupling constant (7.1 Hz) of the anomeric proton signal at δ H 4.50 (H-1‴). The significantly downfield-shifted aromatic proton signal at δ H 6.81 (H-2″) suggested the glucose moiety was attached to C-3″ through an ether linkage.…”

“…788.3983) in its HRFDMS spectrum, which was one glucose unit higher than that of 6 , indicating that two glucose units had been introduced into the molecule of 1 . The additional proton signals at δ H 4.64, 4.51 and 3.71–3.18 (12H), as well as the carbon signals at δ C 103.5, 101.5, 77.1, 76.9, 76.8, 75.8, 73.5, 73.4, 69.7, 69.6, 60.7, and 60.7 observed in the 1 H and 13 C NMR spectra of 7 , indicated the presence of two D-glucose residues [ 24 , 25 ]. The glucose units were identified as β-glucose by their large coupling constants (6.5 Hz and 6.6 Hz) of the anomeric proton signals δ H 4.64 and 4.51, respectively.…”

“…The culture fermentation was carried out according to the usual two-stage procedure [ 24 , 25 , 26 ]. In the screening studies, the actively growing microbial cultures were inoculated in 250 mL flasks containing 50 mL of media and incubated in a temperature-controlled shaking incubator with gentle agitation (200 rpm) at 25 °C for one day.…”

“…The cytotoxic activities of all the compounds ( 1 – 11 ) were evaluated using the MTT assay [ 24 , 28 ]. Briefly, the A375P (human melanoma), B16F10 and B16F1 (mouse melanoma) cell lines obtained from the Korean Cell Line Bank (Seoul, Korea) were cultured in Dulbecco’s Modified Eagle’s Medium (DMEM) (Gibco, CA, USA) containing penicillin (100 units/mL)-streptomycin (100 µg/mL) (Gibco, CA, USA) and 5% heat-inactivated fetal bovine serum (FBS) (Welgene, Korea) in a humidified chamber with 5% CO 2 at 37 °C.…”

Biotransformation of (−)-α-Bisabolol by Absidia coerulea

“…Microbial transformation is a well-established green technique with high selectivity and efficiency to produce new and unique derivatives of bioactive substrates which are difficult to acquire by chemical synthesis under mild conditions [ 20 , 21 ]. It has been reported that microbial transformation of sesquiterpenes can result in derivatives with enhanced biological activities [ 22 , 23 ].…”