Aminoglycoside Antibiotics: New Insights into the Biosynthetic Machinery of Old Drugs

2‐Deoxystreptamine (2DOS) is the unique chemically stable aminocyclitol scaffold of clinically important aminoglycoside antibiotics such as neomycin, kanamycin, and gentamicin, which are produced by Actinomycetes. The 2DOS core can be decorated with various deoxyaminosugars to make structurally diverse pseudo‐oligosaccharides. After the discovery of biosynthetic gene clusters for 2DOS‐containing aminoglycoside antibiotics, the function of each biosynthetic enzyme has been extensively elucidated. The common biosynthetic intermediates 2DOS, paromamine and ribostamycin are constructed by conserved enzymes encoded in the gene clusters. The biosynthetic intermediates are then converted to characteristic architectures by unique enzymes encoded in each biosynthetic gene cluster. In this Personal Account, we summarize both common biosynthetic pathways and the pathways used for structural diversification.

     

Separation of three anthraquinone glycosides including two isomers by preparative high‐performance liquid chromatography and high‐speed countercurrent chromatography from Rheum tanguticum Maxim. ex Balf

Anthraquinone glycosides, such as chrysophanol 1‐O‐β‐d‐ glucoside, chrysophanol 8‐O‐β‐d‐ glucoside, and physion 8‐O‐β‐d‐ glucoside, are the accepted important active components of Rheum tanguticum Maxim. ex Balf. due to their pharmacological properties: antifungal, antimicrobial, cytotoxic, and antioxidant activities. However, an effective method for the separation of the above‐mentioned anthraquinone glycosides from this herb is not currently available. Especially, greater difficulty existed in the separation of the two isomers chrysophanol 1‐O‐β‐d‐ glucoside and chrysophanol 8‐O‐β‐d‐ glucoside. This study demonstrated an efficient strategy based on preparative high‐performance liquid chromatography and high‐speed countercurrent chromatography for the separation of the above‐mentioned anthraquinone glycosides from Rheum tanguticum Maxim.ex Balf.     

1H and 13C NMR assignments for two new angular furanocoumarin glycosides from Peucedanum praeruptorum

Two novel angular-type furanocoumarin glycosides, peucedanoside A (1) and peucedanoside B (2), along with a known compound apterin (3), were isolated from the roots of Peucedanum praeruptorum Dunn. Their chemical structures were determined by MS, NMR spectroscopy and chemical analysis. Complete assignments of the 1H and 13C NMR spectroscopic data were achieved by 1D and 2D NMR experiments including DEPT, HSQC, HMBC and ROESY.     

阿拉善马先蒿植物中单萜环烯醚甙的研究

阿拉善马先蒿(Pedicularis alaschania maxim)系玄参科马先蒿属植物,民间可代替夏枯草入药,主治淋巴结核、淋巴腺炎、高血压和甲状腺肿大等疾病。其化学成分研究尚未见报道。我们从马先蒿中分离得到2个单萜环烯醚甙P1和P2。P2经质谱(FAB MS)、核磁共振谱(~1H和~(13)C NMR)和红外光谱等数据与文献对照确定为桃叶珊瑚甙(aucubin)。P1为一新化合物。本文报道它们的分离与鉴定。     

马先蒿属植物苯丙素甙成分研究(Ⅰ)

近年来,由苯丙素和糖组成的苯丙素甙由于具有药理活性而受到人们的重视^[1～4].本文报道从穗花马先蒿(Pedicularis spicata)中分得的2个新苯丙素甙,马先蒿甙G(1)和H(2).     

Screening the Key Region of Sunlight Regulating the Flavonoid Profiles of Young Shoots in Tea Plants (Camellia sinensis L.) Based on a Field Experiment

Both UV and blue light have been reported to regulate the biosynthesis of flavonoids in tea plants; however, the respective contributions of the corresponding regions of sunlight are unclear. Additionally, different tea cultivars may respond differently to altered light conditions. We investigated the responses of different cultivars (‘Longjing 43’, ‘Zhongming 192’, ‘Wanghai 1’, ‘Jingning 1’ and ‘Zhonghuang 2’) to the shade treatments (black and colored nets) regarding the biosynthesis of flavonoids. For all cultivars, flavonol glycosides showed higher sensitivity to light conditions compared with catechins. The levels of total flavonol glycosides in the young shoots of different tea cultivars decreased with the shade percentages of polyethylene nets increasing from 70% to 95%. Myricetin glycosides and quercetin glycosides were more sensitive to light conditions than kaempferol glycosides. The principal component analysis (PCA) result indicated that shade treatment greatly impacted the profiles of flavonoids in different tea samples based on the cultivar characteristics. UV is the crucial region of sunlight enhancing flavonol glycoside biosynthesis in tea shoots, which is also slight impacted by light quality according to the results of the weighted correlation network analysis (WGCNA). This study clarified the contributions of different wavelength regions of sunlight in a field experiment, providing a potential direction for slightly bitter and astringent tea cultivar breeding and instructive guidance for practical field production of premium teas based on light regimes.     

亲水相互作用色谱-串联质谱法测定液体食品中14种甜味剂

建立了亲水相互作用色谱-三重四极杆质谱（HILIC-MS/MS）同时测定液体食品中6种人工合成甜味剂和8种甜菊糖苷类天然甜味剂的分析方法。样品经Waters Xbridge Amide色谱柱（150 mm×5.0 mm,3.5 μm）分离,以乙腈-10 mmol/L甲酸铵溶液（65：35,v/v）为流动相,流速为0.4 mL/min,柱温为35℃,然后以电喷雾电离（ESI）源,在多反应监测（MRM）、负离子模式下进行三重四极杆质谱检测。14种甜味剂在各自的范围内线性关系良好,相关系数均大于0.995,检出限为0.03~0.7 mg/kg,定量限为0.1~2.2 mg/kg。在2、5和20 mg/kg添加水平下,14种甜味剂的平均回收率为80.8%~108.7%,相对标准偏差为1.5%~7.7%（n=6）。该方法样品前处理操作简单,准确度高,灵敏度高,可用于液体食品中14种甜味剂的同时测定。