Flavonoids inhibit both rice and sheep serotonin N‐acetyltransferases and reduce melatonin levels in plants

The plant melatonin biosynthetic pathway has been well characterized, but inhibitors of melatonin synthesis have not been well studied. Here, we found that flavonoids potently inhibited plant melatonin synthesis. For example, flavonoids including morin and myricetin significantly inhibited purified, recombinant sheep serotonin N‐acetyltransferase (SNAT). Flavonoids also dose‐dependently and potently inhibited purified rice SNAT1 and SNAT2. Thus, myricetin (100 μmol/L) reduced rice SNAT1 and SNAT2 activity 7‐ and 10‐fold, respectively, and also strongly inhibited the N‐acetylserotonin methyltransferase activity of purified, recombinant rice caffeic acid O‐methyltransferase. To explore the in vivo effects, rice leaves were treated with flavonoids and then cadmium. Flavonoid‐treated leaves had lower melatonin levels than the untreated control. To explore the direct roles of flavonoids in melatonin biosynthesis, we first functionally characterized a putative rice flavonol synthase (FLS) in vitro and generated flavonoid‐rich transgenic rice plants that overexpressed FLS. Such plants produced more flavonoids but less melatonin than the wild‐type, which suggests that flavonoids indeed inhibit plant melatonin biosynthesis.     

中药石斛黄酮活性成分研究进展

石斛是益胃生津,滋阴补虚的中药,有提高免疫力、抗氧化等功效,含有丰富的黄酮活性成分,具有较高保健价值。从多个石斛中共分离得到89个黄酮活性成分,主要分为黄酮类、黄烷酮类、黄酮醇类3种。其中黄酮类成分40个,苷元类型主要为芹菜素和圣金草素;黄烷酮类成分20个;黄酮醇类成分15个,苷元类型主要为山柰酚和槲皮素。铁皮石斛及个别种还含有二氢黄酮醇类、花色素类、查尔酮类等黄酮类型成分。含有黄酮活性成分的石斛属植物有34个种,铁皮石斛含38个黄酮成分,霍山石斛含28个黄酮成分,紫皮石斛(齿瓣石斛)含19个黄酮成分,大苞鞘石斛含12个黄酮成分,球花石斛含有5个黄酮成分,叠鞘石斛和棒节石斛各含有4个黄酮活性成分。霍山石斛中含有大量以芹菜素为苷元的黄酮活性成分,紫皮石斛中含有多数以山柰酚或槲皮素为苷元的黄酮活性成分。常见的黄酮活性成分有柚皮素、槲皮素、芦丁等,具有抗氧化、降血糖、可改善血液循环、降低胆固醇,对心血管系统具有保护作用等药理活性作用。笔者拟对中药石斛黄酮活性成分的数量、类型、生理功能等研究现状进行了综述,以期推动药用石斛业内对石斛黄酮的关注,有助于挖掘石斛属植物在药效、食品领域的价值。     

Enzymatic synthesis of myricetin 3-O-galactoside through a whole-cell biocatalyst

Objective: Myricetin 3-O-galactoside is an active compound with pharmaceutical potential. The insufficient supply of this compound becomes a bottleneck in the druggability study of myricetin 3-O-galactoside. Thus, it is necessary to develop a biosynthetic process for myricetin 3-O-galactoside through metabolic engineering. Methods: Two genes OcSUS1 and OcUGE1 encoding sucrose synthase and UDP-glucose 4-epimerase were introduced into BL21(DE3) to reconstruct a UDP-D-galactose (UDP-Gal) biosynthetic pathway in Escherichia coli. The resultant chassis strain was able to produce UDP-Gal. Subsequently, a flavonol 3-O-galactosyltransferase DkFGT gene was transformed into the chassis strain producing UDP-Gal. An artificial pathway for myricetin 3-O-galactoside biosynthesis was thus constructed in E. coli. Results: The obtained engineered strain was demonstrated to be capable of producing myricetin 3-O-galactoside, reaching 29.7 mg/L. Conclusion: Biosynthesis of myricetin 3-O-galactoside through engineered E. coli could be achieved. This result lays the foundation for the large-scale preparation of myricetin 3-O-galactoside.     

思茅豆腐柴中的黄酮类化学成分研究

 目的研究民族药物思茅豆腐柴(Premna szemaoensis Pei)中的黄酮类化学成分。方法利用Sephadex LH-20及硅胶等色谱技术进行分离纯化,根据理化性质、光谱数据进行结构鉴定。结果得到7个黄酮类化合物,分别鉴定为5,4'-二羟基- 3,7,3'-三甲氧基黄酮(1),5-羟基-3',4',6,7-四甲氧基黄酮(2),5,4'-二羟基-7-甲氧基黄酮醇(3),5,3'-二羟基-7,4'-二甲氧基黄酮醇(4),3',4',5-三羟基-3,7-二甲氧基黄酮(5),5,7-二羟基-4'-甲氧基黄酮(6),5-羟基-7,3',4'-三甲氧基黄酮醇(7)。结论这7个化合物均为首次从思茅豆腐柴中分离得到。     

胭脂花化学成分的研究Ⅱ

 目的研究报春花科报春花属植物胭脂花(Primula maximowiczii Regel)的化学成分。方法运用多种色谱方法,从胭脂花全草中分离得到9个化合物,通过理化性质和波谱数据鉴定化合物的结构。结果分离得到的化合物结构为:山柰酚3-O-β-D-葡萄糖基(1→2)-β-D-葡萄糖基(1→6)-β-D-葡萄糖苷(1),山柰酚3-O-(2″,6″-二-O-α-L-鼠李糖基)-β-D-半乳糖苷(2),槲皮素3-O-(2″,6″-二-O-α-L-鼠李糖基)-β-D-半乳糖苷(3),山柰酚3-O-β-D-半乳糖苷(4),槲皮素3-O-β-D-半乳糖苷(5),杨梅素3-O-β-D-半乳糖苷(6),山柰酚3-O-(2″,6″-二-O-α-L-鼠李糖基)-β-D-葡萄糖苷(7),槲皮素3-O-(2″,6″-二-O-α-L-鼠李糖基)-β-D-葡萄糖苷(8),樱草苷(9)。结论化合物1为新化合物,化合物2～8为首次从该属植物中分离得到,化合物9为首次从胭脂花中分离得到,同时本实验将化合物9的¹³C-NMR数据补充完整。     

斜方复叶耳蕨的化学成分研究

目的:对斜方复叶耳蕨Arachniodes rhomboidea地上部分进行化学成分分离鉴定。方法:采用不同色谱技术进行分离,用波谱和化学方法确定化合物结构。结果:分离鉴定6个黄酮醇类化合物,分别为山柰酚(1)、山柰素-3-O-α-L-鼠李糖苷(2)、山柰素-3-O-β-D-葡萄糖苷(3)、山柰素-3,7-O-α-L-鼠李糖苷(4)、槲皮素-3-O-β-D-葡萄糖苷(5)、山柰素-3-O-β-D-芸香糖苷(6)。结论:所有化合物均为首次从该植物中得到。     

藏药五脉绿绒蒿中非生物碱成分

目的:研究藏药五脉绿绒蒿Meconopsis quintuplinervia的化学成分。方法:应用色谱技术分离纯化,用波谱学方法确定化合物结构。结果:从乙醇提取物中分离得到12个化合物,分别鉴定为:槲皮素-3-O-β-D-葡萄糖苷(Ⅰ),槲皮素-3-O-[β-D-半乳糖(1→6)]-β-D-葡萄糖苷(Ⅱ),山柰素-3-O-[β-D-葡萄糖(1→2)]-β-D-葡萄糖苷(Ⅲ),异鼠李黄素-3-O-[β-D-半乳糖苷(1→6)]-β-D-葡萄糖(Ⅳ),咖啡酸(Ⅴ),原儿茶酸(Ⅵ),对羟基肉桂酸(Ⅶ),2-(3,4-二羟苯基)-乙醇β-D-吡喃葡萄糖苷(Ⅷ),对羟基苯甲酸β-D-吡喃葡萄糖酯苷(Ⅸ),肉桂酸4-O-β-D-吡喃葡萄糖苷(Ⅹ),5,7-二羟基色原酮(Ⅺ),胡萝卜苷(Ⅻ)。结论:除Ⅵ和Ⅻ外,其余10个化合物均为首次从该属植物中发现。     

基于抗氧化反应元件的药物筛选模型的建立

目的建立基于抗氧化反应元件(antioxident responseelement,ARE)和SEAP报告基因的细胞筛选模型,用此模型对金雀异黄素、芹菜苷配基、儿茶素、茨非醇4种化合物进行活性比较,观察上述化合物拮抗过氧化氢损伤的作用,寻找具有强抗氧化活性作用的黄酮类化合物。方法构建重组报告基因表达载体pARE-TAL-SEAP与对照载体分别转染HEK-293细胞,检测上述黄酮类化合物作用后对SEAP的活性和抗氧化作用的影响。结果在加入25μmol.L-1H2O2进行氧化损伤的HEK-293细胞中,加入100μmol.L-1的4种化合物进行比较时金雀异黄素的抗氧化作用最强,金雀异黄素诱导SEAP的最大表达水平较对照孔升高1.3倍;加入25μmol.L-14种化合物的抗氧化作用时茨非醇的抗氧化作用最强,茨非醇诱导SEAP的最大表达水平较对照孔升高1.5倍。结论利用此模型可以检测H2O2的氧化应激反应并可筛选到抗氧化活性强的黄酮类化合物。     

黔岭淫羊藿化学成分的研究Ⅰ

 目的:对黔岭淫羊藿(Epimedium leptorrhizumStearm.)的化学成分进行分离,并鉴定其化学结构?方法:采用柱层析方法进行分离,用UV,IR,MS,¹H-NMR和¹³C-NMR等光谱技术鉴定化合物的结构?结果:从醋酸乙酯部分分离到4个化合物,经鉴定为:thalictoside(Ⅰ),2″-鼠李糖基淫-羊藿次苷Ⅱ[2″-O-rhamnosyl-icarisidⅡ(Ⅱ)],箭藿苷A[sagitatosideA(Ⅲ)],大花淫羊藿苷B[ikarisosideB(Ⅳ)]?结论:化合物Ⅰ为苯酚苷类化合物,化合物Ⅱ,Ⅲ,Ⅳ为8-异戊烯基黄酮苷类化合物,4个化合物均为首次从该植物中分离得到?     

Additional antiprotozoal flavonol glycosides of the aerial parts of Helianthemum glomeratum

Bioassay-guided fractionation of the methanol extract of aerial parts from Helianthemum glomeratum afforded five antiprotozoal flavonol glycosides: tiliroside, kaempferol-3-O-(3',6'di-O-E-p-coumaroyl)-betad-glucopyranoside, astragalin, quercitrin and isoquercitrin. The in vitro antiprotozoal assay showed that tiliroside was the most potent antiamoebic and antigiardial compound with IC(50) values of 17.5 microg/mL for Entamoeba histolytica and 17.4 microg/mL for G. lamblia. Isoquercitrin showed selectivity against E. histolytica (IC(50) 14.7 microg/mL) and quercitrin toward G. lamblia (IC(50) 24.3 microg/mL). All isolated compounds were less active than metronidazole and emetine, two antiprotozoal drugs used as positive controls.