Giorgis Isaac

Dr. Giorgis Isaac


Research Focus & Metrics

Academic Career Length

13Years (2014-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 August 2014 in Journal of Lipid Research
Verified
Journal Article
Open access
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CDCarola W. N. Damen
Carola W. N. Damen
GIGiorgis Isaac
Giorgis Isaac
JLJames Langridge
James Langridge
THThomas Hankemeier
Thomas Hankemeier
RVRob Vreeken
Rob Vreeken
An ultraperformance LC (UPLC) method for the separation of different lipid molecular species and lipid isomers using a stationary phase incorporating charged surface hybrid (CSH) technology is described. The resulting enhanced separation possibilities of the method are demonstrated using standards and human plasma extracts. Lipids were extracted from human plasma samples with the Bligh and Dyer method. Separation of lipids was achieved on a 100 × 2.1 mm inner diameter CSH C18 column using gradient elution with aqueous-acetonitrile-isopropanol mobile phases containing 10 mM ammonium formate/0.1% formic acid buffers at a flow rate of 0.4 ml/min. A UPLC run time of 20 min was routinely used, and a shorter method with a 10 min run time is also described. The method shows extremely stable retention times when human plasma extracts and a variety of biofluids or tissues are analyzed [intra-assay relative standard deviation (RSD) <0.385% and <0.451% for 20 and 10 min gradients, respectively (n = 5); interassay RSD <0.673% and <0.763% for 20 and 10 min gradients, respectively (n = 30)]. The UPLC system was coupled to a hybrid quadrupole orthogonal acceleration time-of-flight mass spectrometer, equipped with a traveling wave ion-mobility cell. Besides demonstrating the separation for different lipids using the chromatographic method, we demonstrate the use of the ion-mobility MS platform for the structural elucidation of lipids. The method can now be used to elucidate structures of a wide variety of lipids in biological samples of different matrices.

Verified
Journal Article
Open access
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YWYan-Hong Wang
Yan-Hong Wang
YMYonghai Meng
Yonghai Meng
CZChunmei Zhai
Chunmei Zhai
MWMei Wang
Mei Wang
BABharathi Avula
Bharathi Avula
IKIkhlas Khan
Ikhlas Khan
Eleutherococcus senticosus Maxim. belongs to the Araliaceae family. Phytochemical studies reveal that E. senticosus leaves contain triterpene glycosides along with organic acid derivatives and flavonoid compounds. It is believed that E. senticosus is similar to ginseng because they come from same family and both contain triterpene saponins. E. senticosus leaves have been developed as a functional beverage called ci-wu-jia tea in recent years. Triterpene glycosides are difficult to identify by ultraviolet (UV) detection and contents of these compounds are low in E. senticosus leaves. In this study, a sensitive ultra-high performance liquid chromatographic (UHPLC) method combining UV and tandem mass spectrometry (MS/MS) was developed to characterize the triterpene glycosides from E. senticosus leaves and related commercial products. Fragmentation patterns of three sub-groups of triterpene glycosides in E. senticosus leaves were investigated. Additionally, fragmentation pathways and UV characteristics of organic acid derivatives and flavonoids were also characterized. A compound screening library, including 241 compounds reported in the literature, was created and used to confirm the compounds in the samples. In this study, a total of 24 samples, including 13 plant samples of E. senticosus and 11 ci-wu-jia tea products, were analyzed. Out of the 11 commercial products, three products were discovered to contain green tea (Camellia sinensis) that was considered to be an adulterant since it was not an ingredient on the labels. The developed UHPLC-UV-MS/MS analytical method combined with the UNIFI processing method can simultaneously characterize organic acid derivatives, flavonoids, and triterpene saponins from E. senticosus. It provides a simple and sensitive way to perform quality control of E. senticosus and related ci-wu-jia tea products.

27 August 2019 in Molecules
Verified
Journal Article
Open access
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XNXuehong Nöst
Xuehong Nöst
EPEva-Maria Pferschy-Wenzig
Eva-Maria Pferschy-Wenzig
SNStefanie Nikles
Stefanie Nikles
XHXiaojuan He
Xiaojuan He
DFDanping Fan
Danping Fan
Rudolf BauerRudolf Bauer
Rudolf Bauer
Within non-communicable diseases, chronic inflammatory conditions represent one of the biggest challenges for modern medicine. Traditional Chinese Medicine (TCM) has been practiced over centuries and has accumulated tremendous empirical knowledge on the treatment of such diseases. Huangqi Jianzhong Tang (HQJZT) is a famous TCM herbal formula composed of Radix Astragali, Ramulus Cinnamomi, Radix et Rhizoma Glycyrrhizae Praeparata cum Melle, Radix Paeoniae Alba, Rhizoma Zingiberis Recens, Fructus Jujubae and Saccharum Granorum (maltose), which has been used for the treatment of various chronic inflammatory gastrointestinal diseases. However, there is insufficient knowledge about its active constituents and the mechanisms responsible for its effects. The present study aimed at identifying constituents contributing to the bioactivity of HQJZT by combining in vitro cytokine production assays and LC-MS metabolomics techniques. From the HQJZT decoction as well as from its single herbal components, extracts of different polarities were prepared. Phytochemical composition of the extracts was analyzed by means of UPLC-QTOF-MS/MS. The inhibitory effects of the extracts on TNF-α, IL-1β and IFN-γ production were studied in U937 cells. Phytochemical and pharmacological bioactivity data were correlated by orthogonal projection to latent structures discriminant analysis (OPLS-DA) in order to identify those HQJZT constituents which may be relevant for the observed pharmacological activities. The investigations resulted in the identification of 16 HQJZT constituents, which are likely to contribute to the activities observed in U937 cells. Seven of them, namely calycosin, formononetin, astragaloside I, liquiritigenin, 18β-glycyrrhetinic acid, paeoniflorin and albiflorin were unambiguously identified. The predicted results were verified by testing these compounds in the same pharmacological assays as for the extracts. In conclusion, the anti-inflammatory activity of HQJZT could be substantiated by in vitro pharmacological screening, and the predicted activities of the OPLS-DA hits could be partially verified. Moreover, the benefits and limitations of MVDA for prediction pharmacologically active compounds contributing to the activity of a TCM mixture could be detected.

25 February 2022 in Journal of Chromatography A
Verified
Journal Article
Open access
GIGiorgis Isaac
Giorgis Isaac
Ian WilsonIan Wilson
Ian Wilson
RPRobert Plumb
Robert Plumb
The use of hybrid surface technology (HST), applied to the metal surfaces of an ACQUITY™ UPLC™ system and column, designed to mitigate the chelation, poor peak shape and analyte loss seen with acidic phospholipids was investigated. Compared to a conventional system significant improvements in both sensitivity, recovery and peak shape were obtained following UPLC on a CSH C18 column when the HST was used for the analysis of lysophosphatidic acid (LPA), phosphatidic acid (PA), lysophosphatidylserine (LPS), phosphatidylserine (PS), phosphatidylinositol-monophosphates (PIP), ceramide phosphate (CerP) and sphingoid base phosphate (SPBP). The benefits in chromatographic performance provided by the HST were seen particularly at low concentrations of these analytes. The HST system and column reduced peak tailing by 65-80% and peak width by 70-86% for LPA and PA. Moreover, increased signal intensities of up to 12.7 times were observed for LPA with the HST approach compared to the equivalent untreated LC system and column. The application of this methodology to the analysis of chicken egg PA and brain porcine PS extracts were accompanied by similar improvements in data quality.


17 March 2016 in Planta Medica
Verified
Journal Article
Closed access
YWYh Wang
Yh Wang
BABharathi Avula
Bharathi Avula
GIGiorgis Isaac
Giorgis Isaac
JYJisung Yuk
Jisung Yuk
MWM Wrona
M Wrona
IKIa Khan
Ia Khan
Natural products chemical ingredient profiling is a challenging task because of the sample complexity and the analyses required. For any natural products related study, regardless of the research focus and the final end goal, ingredient profiling (to elucidate the active compounds from a particular plant), sample comparison (to understand point of origin and to prove authenticity), quantification and identification of target compounds for quality control purpose are all routinely required. Because of the complexity of the sample and large amount of data that can be generated using the most popular approach such as LC/MS, researchers are still challenged by how to narrow down the scope and to obtain meaningful information quickly. Three different botanicals (Hoodia, Terminalia and Chamomile) and their respective dietary supplements were used for the study of targeted and non-targeted analysis of compounds. Here, a streamlined workflow was presented that enables researchers to quickly identify chemical ingredients from botanicals and dietary supplements from a single data independent LC/MS injection. The data independent acquisition provides both precursor exact mass and corresponding fragment ion information from a single injection for facile structural characterization. Data are then searched against the Traditional Medicine Scientific Library provided within the informatics platform from the instrument vendor. Structures of matched experimental and in silico corresponding fragment ions are automatically verified by a software tool imbedded within UNIFI informatics platform. Results are displayed automatically using preset workflow and report templates.