Production of Siderophores by an Apple Root-Associated Streptomyces ciscaucasicus Strain GS2 Using Chemical and Biological OSMAC Approaches

Apple Replant Disease (ARD) is a significant problem in apple orchards that causes root tissue damage, stunted plant growth, and decline in fruit quality, size, and overall yield. Dysbiosis of apple root-associated microbiome and selective richness of Streptomyces species in the rhizosphere typically concurs root impairment associated with ARD. However, possible roles of Streptomyces secondary metabolites within these observations remain unstudied. Therefore, we employed the One Strain Many Compounds (OSMAC) approach coupled to high-performance liquid chromatography-high-resolution tandem mass spectrometry (HPLC-HRMSⁿ) to evaluate the chemical ecology of an apple root-associated Streptomyces ciscaucasicus strain GS2, temporally over 14 days. The chemical OSMAC approach comprised cultivation media alterations using six different media compositions, which led to the biosynthesis of the iron-chelated siderophores, ferrioxamines. The biological OSMAC approach was concomitantly applied by dual-culture cultivation for microorganismal interactions with an endophytic Streptomyces pulveraceus strain ES16 and the pathogen Cylindrocarpon olidum. This led to the modulation of ferrioxamines produced and further triggered biosynthesis of the unchelated siderophores, desferrioxamines. The structures of the compounds were elucidated using HRMSⁿ and by comparison with the literature. We evaluated the dynamics of siderophore production under the combined influence of chemical and biological OSMAC triggers, temporally over 3, 7, and 14 days, to discern the strain’s siderophore-mediated chemical ecology. We discuss our results based on the plausible chemical implications of S. ciscaucasicus strain GS2 in the rhizosphere.     

A dereplication strategy for the identification of new phenolic compounds from Anvillea radiata (Coss. & Durieu)

Phenolic compounds were selectively extracted from aerial parts of Anvillea radiata using Accelerated Solvent Extraction (ASE) in two steps. Given the two molecular families (flavonoids and germacranolides) described as present in the plant material, a first extraction step using chloroform as the extraction solvent was carried out to remove the germacranolides, the most abundant compounds. The minor phenolic compounds were then selectively extracted and enriched from the plant residue by methanol. Characterization of twenty five phenolic compounds in the methanolic extract was performed using HPLC-DAD-ESI-MS/MS and HPLC-HRMS analyses. Seven compounds corresponded to chlorogenic acid and dicaffeoylquinic acid derivatives and eighteen flavonoids (from which five aglycones and thirteen glycosides) were identified and some of them for the first time.The presence of these phenolic compounds, identified in the whole aerial parts, was then followed in each organ (flower, leave and stem). The chromatographic profiles of the stem and leave were very close, while the flower one was more different. However most of the compounds identified in aerial parts were recovered in each organ, mainly difference on peak intensity could be observed. The most abundant compound in flowers was found to be a di-caffeoylquinic acid derivative while isorhamnetin and spinacitin diglucoside derivatives were the most abundant ones in stems and leaves.     

基于HPLC-HRMS/MS~n/QqQ技术的人参皂苷Rb_1化学转化产物的结构与途径分析

利用液相色谱-质谱联用技术分析了Keggin型12-磷钨酸化学转化人参皂苷Rb1产物的结构与转化途径.基于高效液相色谱对转化产物的快速分离,利用Q Exactive高分辨质谱的Full MS-AIF模式快速鉴定了产物结构,并利用多级串联质谱进行结构验证.进一步结合人参皂苷异构体在反向C18色谱柱上的相对保留时间,快速分析鉴定出Rb1的10种转化产物为20(S)-Rg3,20(R)-Rg3,20(S)-25-OH-Rg3,20(R)-25-OH-Rg3,25-OH-Rk1,25-OH-Rg5,Rg5,Rk1,(20S,25)-环氧-Rg3和(20R,25)-环氧-Rg3.根据转化产物的结构初步推断了人参皂苷的转化途径:在12-磷钨酸产生的酸性环境中,Rb1主要通过C20位去糖基化、差向异构化和烯烃链的水合、消除及环合反应转化为稀有皂苷.采用三重四极杆质谱的选择反应监测模式准确定量分析了Rb1的转化效率和稀有皂苷20(S)-Rg3,20(R)-Rg3,Rk1和Rg5的产率.定量分析结果显示,与生物转化相比,12-磷钨酸对Rb1有更高的转化效率,反应40 min后转化率达到100%.本文结果表明,HPLC-HRMS/MSn/Qq Q技术是人参皂苷等天然产物结构解析与定量分析的有效方法.     

Determination of Pesticides in Organic Carrots by High-Performance Liquid Chromatography/High-Resolution Mass Spectrometry

Food contamination by pesticide residues, which may cause serious human health problems, is an ongoing challenge. Safer organically grown food is therefore needed. However, best practices are not always followed for farming organic foods, necessitating analytical testing. To this end, this report describes an analytical method for the evaluation of 82 pesticides by high-performance liquid chromatography–high-resolution mass spectrometry in organically grown carrots. The method was validated in terms of linearity, precision, and limits of detection and quantification that ranged from 0.3 to 5 and 5–40?µg?kg^?1, respectively. From the 82 pesticides evaluated in this multiresidue method, three were detected in real samples, with bendiocarb detected at the highest concentration (199.11?µg?kg^?1), which was above the maximum residue limit. Chlorpyriphos (43.20?µg?kg^?1) and amitraz (11.22?µg?kg^?1) were also detected. Measurement of contaminants in organic foods should be a standard practice, which would contribute to improved food safety. It is observed that even organic foods can be contaminated by pesticides, intentionally or unintentionally, perhaps by cross-contamination. Pesticides in organic foods are a public health problem because consumers expect organic foods to be free of pesticide contamination, but this is not necessarily the case.     

高效液相色谱-高分辨质谱快速筛查和确证保健品中非法添加的壮阳药物

采用高效液相色谱-四极杆/飞行时间质谱对中药保健品中红地那非、伐地那非、那红地那非、他达拉非、西地那非、豪莫西地那非、硫代艾地那非、伪伐地那非、羟基豪莫西地那非、育亨宾、达泊西汀等11种非法添加的壮阳类药物进行了快速筛查、确证和定性定量检测。样品经甲醇提取后,采用正离子扫描模式进行检测。结果表明,11种待测物的定量限除那红地那非为25.0 ng/mL外,其他10种壮阳类药物均为5.0 ng/mL,在5.0~200.0 ng/mL(那红地那非在25.0~500.0 ng/mL)范围内,线性相关性较好,相关系数均不小于0.9990。平均添加回收率为82.0%~105.9%,相对标准偏差为4.7%~16.5%。本方法利用准确质量数匹配和自建标准谱库,通过多级特征碎片离子的比对,实现快速筛查和确证,简单快速,结果可靠。