竹叶黄酮的酶促酰化、分离与结构鉴定

研究了固定化脂肪酶B（Novozmy 435）在低水分含量的叔戊醇溶剂中催化竹叶黄酮与硬脂酸的酰化反应。反应条件:竹叶黄酮与硬脂酸酸摩尔比1∶5,脂肪酶用量50g/L,机械搅拌转速200r/min,反应温度50℃,反应时间72h。后经液液萃取,薄层层析（TLC,UV 254nm）,硅胶柱层析分离纯化,薄层层析展开剂配比为氯仿/甲醇/冰乙酸（7∶1∶0.05,v/v/v）,柱层析洗脱剂配比为氯仿/甲醇/冰乙酸（10∶1∶0.05,v/v/v）;洗脱液合并相同组分,得到两种黄酮苷酰化物单体。对纯化后的组分采用红外光谱（IR）、质谱（ESI-MS）、核磁共振（1H-NMR、13C-NMR）进行结构鉴定和表征,确定产物分别为异牡荆苷-6″-硬脂酸酯和异荭草苷-6″-硬脂酸酯,说明反应表现出高度选择性。 

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.