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Tag: Belen Cassera

Antimalarial Diterpenoids From Vitex Rotundifolia: Isolation, Structure Elucidation, and in Vitro Antiplasmodial Activity

Donna Huber on May 12, 2020

Vitex rotundifolia is an important medicinal plant frequently employed in traditional medicines for the treatment of various ailments. Although this plant species has been under exploration for its constituents by various research groups including our own group, no reports were found regarding the antimalarial potential of this plant or of its purified phytochemicals. Phytochemical investigation of this plant yielded three new (1-3) and five known (4-8) diterpenoids. These compounds were purified by modern chromatographic techniques and their structures were determined by advanced spectroscopic techniques such as nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS). The in vitro antiplasmodial activities were encouraging, as compounds 2, 6, and 8 were found to have significant IC50 values of 1.2, 1.3 and 11.0 µM, respectively against Plasmodium falciparum.

You Ah Kim, Abdul Latif, Chang-Suk Kong, Youngwan Seo, Seema R Dalal, Maria B Cassera, David G I Kingston. Bioorg Chem. 2020 May 12;100:103925. doi: 10.1016/j.bioorg.2020.103925.

Galtonosides A-E: Antiproliferative and Antiplasmodial Cholestane Glycosides from Galtonia regalis

Donna Huber on March 31, 2020

An extract of Galtonia regalis from the Natural Products Discovery Institute showed moderate antiplasmodial activity, with an IC50 value less than 1.25 μg/mL. The two known cholestane glycosides 1 and 2 and the five new cholestane glycosides galtonosides A–E (3–7) were isolated after bioassay-directed fractionation. The structures of the new compounds were determined by interpretation of their NMR and mass spectra. Among these compounds, galtonoside B (4) displayed the most potent antiplasmodial activity, with an IC50 value of 0.214 μM against the drug-resistant Dd2 strain of Plasmodium falciparum.

Yongle Du, Brooke A. Martin, Ana Lisa Valenciano, Jason A. Clement, Michael Goetz, Maria B. Cassera, David G. I. Kingston. J Nat Prod. 2020 Mar 31. doi: 10.1021/acs.jnatprod.9b01064.

Anibamine and Its Analogues: Potent Antiplasmodial Agents from Aniba citrifolia

Donna Huber on October 2, 2019

In our continuing search for novel natural products with antiplasmodial activity, an extract of Aniba citrifolia was found to have good activity, with an IC50 value less than 1.25 μg/mL. After bioassay-directed fractionation, the known indolizinium alkaloid anibamine (1) and the new indolizinium alkaloid anibamine B (2) were isolated as the major bioactive constituents, with antiplasmodial IC50 values of 0.170 and 0.244 μM against the drug-resistant Dd2 strain of Plasmodium falciparum. The new coumarin anibomarin A (3), the new norneolignan anibignan A (5), and six known neolignans (7–12) were also obtained. The structures of all the isolated compounds were determined based on analyses of 1D and 2D NMR spectroscopic and mass spectrometric data, and the absolute configuration of anibignan A (5) was assigned from its ECD spectrum. Evaluation of a library of 28 anibamine analogues (13–40) indicated that quaternary charged analogues had IC50 values as low as 58 nM, while uncharged analogues were inactive or significantly less active. Assessment of the potential effects of anibamine and its analogues on the intraerythrocytic stages and morphological development of P. falciparum revealed substantial activity against ring stages for compounds with two C-10 side chains, while those with only one C-10 side chain exhibited substantial activity against trophozoite stages, suggesting different mechanisms of action.

Yongle Du, Ana Lisa Valenciano, Yumin Dai, Yi Zheng, Feng Zhang, Yan Zhang, Jason Clement, Michael Goetz, David G. I. Kingston, Maria B. Cassera. 2019. J Nat Prod. doi: 10.1021/acs.jnatprod.9b00724.

Metabolic dependency of chorismate in Plasmodium falciparum suggests an alternative source for the ubiquinone biosynthesis precursor

Donna Huber on September 26, 2019

The shikimate pathway, a metabolic pathway absent in humans, is responsible for the production of chorismate, a branch point metabolite. In the malaria parasite, chorismate is postulated to be a direct precursor in the synthesis of p-aminobenzoic acid (folate biosynthesis), p-hydroxybenzoic acid (ubiquinone biosynthesis), menaquinone, and aromatic amino acids. While the potential value of the shikimate pathway as a drug target is debatable, the metabolic dependency of chorismate in P. falciparum remains unclear. Current evidence suggests that the main role of chorismate is folate biosynthesis despite ubiquinone biosynthesis being active and essential in the malaria parasite. Our goal in the present work was to expand our knowledge of the ubiquinone head group biosynthesis and its potential metabolic dependency on chorismate in P. falciparum. We systematically assessed the development of both asexual and sexual stages of P. falciparum in a defined medium in the absence of an exogenous supply of chorismate end-products and present biochemical evidence suggesting that the benzoquinone ring of ubiquinones in this parasite may be synthesized through a yet unidentified route.

Ana Lisa Valenciano, Maria L. Fernández-Murga, Emilio F. Merino, Nicole R. Holderman, Grant J. Butschek, Karl J. Shaffer, Peter C. Tyler & Maria Belen Cassera. 2019. Sci Rep.;9(1):13936. doi: 10.1038/s41598-019-50319-5.

Isolation and characterization of antiplasmodial constituents from the marine sponge Coscinoderma sp.

Donna Huber on August 6, 2019

Six known compounds, namely two halisulfates 1 and 2 and four epidioxy sterols 3–6, were isolated from the marine sponge Coscinoderma sp. The structures of these compounds were confirmed by nuclear magnetic resonance (1H and 13C NMR) spectroscopy, and their antiplasmodial activities were determined against the chloroquine-resistant Dd2 strain of Plasmodium falciparum. The epidioxy steroids 3–6 all showed moderate to weak antiplasmodial activity, with IC50 values of 2.7 μM for (24S)-5α,8α-epidioxy-24-methylcholesta-6-en-3β-ol (3), 11.6 μM for 5α,8α-epidioxycholesta-6,24(28)-dien-3β-o1 (4), 2.33 μM for 5α,8α-epidioxy-24-methylcholesta-6,9(11)-24(28)-trien-3β-ol (5), and between 12 and 24 μM for 5α,8α-epidioxycholesta-6-en-3β-ol (6). In contrast, halisulfate 2 (1) was inactive, and halisulfate 1 (2) had an of IC50 value of about 24 μM.

Jeong H, Latif A, Kong CS, Seo Y, Lee YJ, Dalal SR, Cassera MB, Kingston DGI. Z Naturforsch C. 2019 Aug 6. pii: /j/znc.ahead-of-print/znc-2019-0039/znc-2019-0039.xml. doi: 10.1515/znc-2019-0039.

Researchers receive $2M NIH instrumentation grant

Donna Huber on January 8, 2019

by Alan Flurry

The National Institutes of Health has awarded University of Georgia researchers $1.956 million for a high-resolution mass spectrometer that will enhance capabilities for scientists in many fields across campus.

The award by the NIH High End Instrumentation program, which provides grants in the range of $600,000 to $2 million for a variety of expensive instrumentation, including MRI imagers, electron microscopes, DNA sequencers, and mass spectrometers, was one of 30 awards made in the program, and one of only six mass spectrometer requests funded in the 2018 cycle.

The grant funded a 12 Tesla Bruker Solarix FTMS, a high-resolution mass spectrometer capable of measuring molecular weights with precision accuracy that can be applied to molecules ranging in size from small metabolic products to intact proteins and protein complexes. It can also provide molecular structure through a multidimensional analysis method known as tandem mass spectrometry. The instrument will be used to support research in metabolomics and glycomics, the analysis of genetic, physiologic and pathologic aspects of sugar molecules involved in all biological process from modulating cell function to determining cancer development.

“This instrument will enhance the research capabilities for a number of scientists in chemistry, the biological sciences and biomedical research, and will help foster interdisciplinary research projects between groups in a number of departments and colleges at the university,” said Jon Amster, professor and head of the department of chemistry and principal investigator on the grant.

Over a dozen researchers will be major users of this instrument, which will be housed in the Amster laboratory in the department of chemistry.

“The new 12T FT-ICR instrument will greatly improve our ability to perform metabolomics analysis, especially regarding to the identification of unknown metabolites, since this instrument has higher accuracy and resolving power than the current instruments at UGA,” said Belen Cassera, associate professor of biochemistry and molecular biology, member of the Center for Tropical and Emerging Global Diseases, and co-principal investigator on the grant. “This type of grant can be particularly difficult to obtain and it is a privilege for me to be part of an amazing team of investigators that put together this application.”

“Virtually every metabolomics project we have going right now will benefit from this new instrumentation grant,” said Art Edison, GRA Eminent Scholar, professor of biochemistry and molecular biology, and a co-principal investigator on the grant. “High resolution mass spectrometry is a very important tool for the analysis of complex biological mixtures and unknown metabolite identification in applications ranging from human disease to carbon cycling in the ocean to model organisms for pathway analysis.”

Of the 104 NIH shared instrumentation grants made this year during 2018, only 10 were in the range of $1.9 million to $2 million.

Phloroglucinols from the Roots of Garcinia dauphinensis and Their Antiproliferative and Antiplasmodial Activities

Donna Huber on October 24, 2018

Graphica abstract

Abstract

Garcinia dauphinensis is a previously uninvestigated endemic plant species of Madagascar. The new phloroglucinols dauphinols A–F and 3′-methylhyperjovoinol B (1–7) and six known phloroglucinols (8–13) together with tocotrienol 14 and the three triterpenoids 15–17 were isolated from an ethanolic extract of G. dauphinensis roots using various chromatographic techniques. The structures of the isolated compounds were elucidated by NMR, MS, optical rotation, and ECD data. Theoretical ECD spectra and specific rotations for 2 were calculated and compared to experimental data in order to assign its absolute configuration. Among the compounds tested, 1showed the most promising growth inhibitory activity against A2870 ovarian cancer cells, with IC50= 4.5 ± 0.9 μM, while 2 had good antiplasmodial activity against the Dd2 drug-resistant strain of Plasmodium falciparum, with IC50 = 0.8 ± 0.1 μM.

Rolly G. Fuentes, Kirk C. Pearce, Yongle Du, Andriamalala Rakotondrafara, Ana L. Valenciano, Maria B. Cassera, Vincent E. Rasamison, T. Daniel Crawford, and David G. I. Kingston. 2018. Journal of Natural Products.
DOI: 10.1021/acs.jnatprod.8b00379

Trainee Spotlight: Josh Butler

Donna Huber on September 18, 2018

Josh Butler

New T32 trainee Josh Butler is a third year Ph.D. student in Belen Cassera‘s laboratory. He is from Front Royal, Virginia and completed his B.S. in chemistry at James Madison University in Harrisonburg, Virginia.

Butler decided to pursue his graduate degree at the University of Georgia because of the Integrate Life Sciences program which offers the opportunity to explore a range of research topics. The same interdisciplinary aspect is what he found appealing about the Center for Tropical and Emerging Global Diseases and ultimately why he joined a lab within this department.

“There is no shortage of resources here, ranging from state of the art instrumentation and core facilities to people that are willing to mentor and train successful scientists,” said Butler. “Coming from a smaller institution, I had never really seen anything to this scale and I knew it was something I wanted to experience and become a part of.”

Research Focus

Broadly, Butler’s research is focused on antimalarial drug discovery. More specifically, he is using antimalarial natural products as tools to discover novel drug targets in the malaria parasite Plasmodium falciparum.

Nearly 220 million people have malaria, and it kills nearly half a million people each year. Plasmodium falciparum causes the most severe forms of malaria, such as cerebral malaria, which can lead to brain damage, coma, and death, and placental malaria, which can be life-threatening to both mother and fetus.

“I chose this research because not only does it contribute positively to the global campaign of malaria eradication, but from a training standpoint it would also provide a solid foundation for a career further researching and developing antimicrobial therapies in general.”

Capstone Experience

Each T32 trainee is provided with the opportunity to pursue a capstone experience. Butler hopes to do an internship with a pharmaceutical industry research group that is actively performing anti-parasitic research to experience how the type research he does as a graduate student can translate outside the realm of academia.

“Private-public collaboration in malaria research has really driven drug discovery research in a positive direction and  I would like the opportunity to experience that first hand and develop acumen to engage in that type of research in the next stage of my career.”

Future Career Goals

“I would like to continue working in a field of scientific research which can positively impact people’s lives, whether it be through a biomedical or biotechnical avenue.”

Advice for Aspiring Scientists

“Don’t be afraid to fail or be wrong. Learn from it and use it to keep pushing forward. Try to find positives in the negatives.”

 

Support trainees like Josh by giving today to the Center for Tropical & Emerging Global Diseases.

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Antiplasmodial flavanones and a stilbene from Carpha glomerata

Donna Huber on September 4, 2018

graphical abstract

Abstract

Bioassay-guided fractionation of an extract of Carpha glomerata (Cyperaceae) led to the isolation of seven compounds. Compounds 1 (carphorin A), 3 (carphorin C), 4(carphorin D), and 5 (carphabene) are new compounds, and compound 2 (8-(3″-hydroxyisoamyl)-naringenin) was isolated for the first time as a natural product. All structures were elucidated based on analyses of their HR-ESIMS and 1D and 2D NMR data. Compounds 1, 2, and 6, which have prenyl or hydroxyprenyl side chains, exhibited antiplasmodial activities with IC50 values of 5.2 ± 0.6, 3.4 ± 0.4, and 6.7 ± 0.8 µM against the drug-resistant Dd2 strain of Plasmodium falciparum. In addition the prenylated stilbene 5 also showed good activity, with IC50 5.8 ± 0.7 µM.

Namki Cho, Ana Lisa Valenciano, Yongle Du, Jason Clement, Maria B. Cassera, Michael Goetz, David G. I. Kingston. 2018. Bioorganic & Medicinal Chemistry Letters; 28(20):3368-3371. https://doi.org/10.1016/j.bmcl.2018.09.003

Visiting Scholar: Elvis Ofori Ameyaw

Donna Huber on February 8, 2018

 

scholar Elvis Ameyaw

Elvis Ofori Ameyaw is a Fulbright Scholar visiting M. Belen Cassera‘s laboratory in the department of molecular biology and biochemistry. He is a senior lecturer, Head of the Department of Biomedical Sciences and the Vice-Dean of the School of Allied Health Sciences in the College of Health and Allied Sciences at the University of Cape Coast in Ghana.

Dr. Ameyaw holds a B. Pharm and Ph.D. in Pharmacology. His research focuses on natural product drug discovery for infectious, in particular, malaria and Leishmania, and inflammatory diseases. At the University of Georgia, he is using in vitro techniques to screen some natural products isolates from plants that are traditionally used to treat malaria in Ghana.

“UGA is globally known for excellent research and education and my host scientist, Prof. M. Belen Cassera has created an envious and reputable niche in natural product research,” said Dr. Ameyaw.

The availability of seminars and other opportunities to interact with leading scientists also factored into Dr. Ameyaw’s decision to come to UGA.

“The research staff at UGA are very supportive and willing to share ideas.” said Dr. Ameyaw.

Athens reminds him of the college town of Cape Coast where he resides and works in Ghana.

“The city makes me feel at home away from home.”

Read more about Dr. Cassera’s natural products research.