Enzymatic acylation,isolation and identification of flavonoid glycosides from bamboo leaves

Immobilised Candida Antarctica lipase B( Novozmy 435) was used to acylate flavonoid glycosides from bamboo leaves in tert- amyl alcohol,with stearic acid as acyl donors at low moisture content.The optimum reaction condition was as follows: a molar ratio of flavonoid glycosides from bamboo leaves to Stearic acid of 1 ∶ 5,50 g / L lipase,stirring speed was 200 r / min,50℃ and reaction time was 72 h.After Liquid- liquid extraction,the products of esterification reactions were subjected to thin- layer chromatography( TLC,UV 254nm),a silica gel column( 700mm× 35 mm,i.d.),the developing solvent ratio was chloroform / methanol / acetic acid( 7∶1∶0.05,v / v / v),and eluted with chloroform / methanol / acetic acid( 10 ∶ 1 ∶ 0.05,v / v / v). Then combine fractions had the same value of retardation factor Rf,two types of acylated flavonoids were obtained. The purified products were analyzed by IR,ESI- MS,1H- NMR and13C- NMR and the two types of acylated flavonoids were isoorientin-6″- stearate and isovitexin-6″-stearate.The enzyme showed strong selectivity for acylation of glycosides.