Pharmacological activity and quantitative analysis of flavonoids isolated from the flowers of Begonia semperflorens Link et Otto

Begonia semperflorens Link et Otto has been broadly raised up for ornamental purpose as well comestible blossom. As the reproductive structures of phanerogams, flowers contain various secondary metabolites and have many biological activities. Accordingly, we began the contrivance for isolation and analysis of flavonoids contained in B. semperflorens flowers. MeOH extraction of B. semperflorens followed solvent fractionation was prosecuted. Column chromatography of non-polar fraction gave four flavonoids using several resins. Identification of the flavonols were established as quercetin (1), kaempferol (2), astragalin (3), and isoquercetin (4) by interpreting a variety of spectral information. Quercetin (1) and kaempferol (2) inhibited NO production and protected against t-BHP-induced oxidative stress. Kaempferol (2) also protected cell death of glutamate-treated HT22. Quantitative analysis of flavonoid content in B. semperflorens flowers was also performed using HPLC experiment.