Screening of potential filamentous fungi Aspergillus sp for biotransformation of quercetin

The major active compounds of mistletoe plant are flavonoid in the glycosides form (quercetin-3-O-rhamnoside) rather than as aglycon (quercetin). Both of quercetin and quercetin-3-O-rhamnoside is well know have wide range biological activities, however quercetin act propenderant function than glicoside. The objective of the present study was to select Aspergillus strains with a potential to perform the biotransformation of quercetin-3-O-rhamnoside converted to be quercetin. Ten Aspergillus strains were cultured in potato dextrose broth using shaker incubator for seven days with and without additional quercetin-3-O-rhamnosides as the substrate, then extracted with ethyl acetate. The extracts were analyzed by TLC and LC-MS/MS. Initially, quercetin-3-O-rhamnoside were extracted from mistletoe (Dendrophthoe curvata (Blume) Miq.) leaf and purified by using solvent-solvent extractions, and elucidation determined based on serial spectrometry data. From the different fungi screened, Aspergillus LS04-3, LS05-3, and LS05-4 showed an extra peak, peak at 3.83 – 4.55 minute in LC-MS/MS and compared to its control, which was confirmed as quercetin. Furthermore, isolation of ethyl acetate extract of LS04-3 with addition of substrate, afforded a bright yellow crystal with MW 446 coincided as quercetin based on MS and compared with a standard. In conclusion LS05-3 (A. versiclor), LS05-4 (A. niger) and especially LS04-3 (A. ascueletus) are valuable microorganism used for flavonol biotransformation.