17 research outputs found
Design and Synthesis of Natural Product-Based Screening Libraries
No full textNatural products (NPs) continue to have significant impact in the area of drug discovery and development. More than 50% of the approved drugs between 1981 and 2014 were either unaltered NPs, NP derivatives or synthetic drugs inspired by NP pharmacophores. NPs have also served as lead molecules in drug development programs; noteworthy example include the semi-synthetic antifungal drugs caspofungin, anidulafungin, and micafungin that were based on NP lead compounds isolated from the fermentation products of various fungus. Other notable examples include the sponge metabolite halichondrin B that was developed into the anticancer drug eribulin, and camptothecin, a plant NP that was developed into the oncology drugs, topotecan and irinotecan.
Many research groups are now utilizing isolated NPs as scaffolds for the generation of semi-synthetic analogue libraries rather than pursuing the total synthesis of a bioactive NP followed by classic medicinal chemistry. This approaches main advantage is the reduction in timelines and resource allocation, which is typically associated with de novo multi-step syntheses of a bioactive NP. Furthermore, once the NP scaffold has been isolated from the source biota rapid analogue generation and subsequent SAR data can be acquired. Thus the evaluation of a scaffold chemotype for potential lead optimization studies is quickly assessed.Thesis (PhD Doctorate)Doctor of Philosophy (PhD)School of Natural SciencesScience, Environment, Engineering and TechnologyFull Tex
Cytotoxic and antibacterial substances against multi-drug resistant pathogens from marine sponge symbiont: Citrinin, a secondary metabolite of Penicillium sp.
No full textObjective: To Isolate, purify, characterize, and evaluate the bioactive compounds from the sponge-derived fungus Penicillium sp. FF001 and to elucidate its structure. Methods: The fungal strain FF001 with an interesting bioactivity profile was isolated from a marine Fijian sponge Melophlus sp. Based on conidiophores aggregation, conidia development and mycelia morphological characteristics, the isolate FF001 was classically identified as a Penicillium sp. The bioactive compound was identified using various spectral analysis of UV, high resolution electrospray ionization mass spectra, 1H and 13C NMR spectral data. Further minimum inhibitory concentrations (MICs) assay and brine shrimp cytotoxicity assay were also carried out to evaluate the biological properties of the purified compound. Results: Bioassay guided fractionation of the EtOAc extract of a static culture of this Penicillium sp. by different chromatographic methods led the isolation of an antibacterial, anticryptococcal and cytotoxic active compound, which was identified as citrinin (1). Further, citrinin (1) is reported for its potent antibacterial activity against methicillin-resistant Staphylococcus aureus (S. aureus), rifampicin-resistant S. aureus, wild type S. aureus and vancomycin-resistant Enterococcus faecium showed MICs of 3.90, 0.97, 1.95 and 7.81 μg/mL, respectively. Further citrinin (1) displayed significant activity against the pathogenic yeast Cryptococcus neoformans (MIC 3.90 μg/mL), and exhibited cytotoxicity against brine shrimp larvae LD50 of 96 μg/mL. Conclusions: Citrinin (1) is reported from sponge associated Penicillium sp. from this study and for its strong antibacterial activity against multi-drug resistant human pathogens including cytotoxicity against brine shrimp larvae, which indicated that sponge associated Penicillium spp. are promising sources of natural bioactive metabolites
Temperature-Responsive Pyraclostrobin-Loaded Octadecane Submicrocapsules with Lowered Toxicity
No full textPyraclostrobin (Pyr) is one of the most effective fungicides. However, it can degrade via photolysis in water, it is toxic to aquatic life and if inhaled, it has a low solubility in water, that leads to difficulties when applying to plants by spraying. Additionally, the necessity of repeated (weekly) sprays of fungicides when the pathogen growth risk is the highest, such as at the temperature range of 24 to 36 °C and increased humidity of about 95%, leads to loss of efficiency of the fungicide and overdose of chemicals. In the present study, pyraclostrobin was microencapsulated to solve the abovementioned issues. As a core of capsules octadecane (OD) with a melting point of 28 °C was used, thus, the release of pyraclostrobin was controlled via temperature change. Pyraclostrobin-loaded submicrocapsules (PyrSMCs) were characterized using SEM, DLS, TGA/DSC, HPLC, FTIR methods; stimuli-responsivity was tested employing in vitro tests with pathogenic culture (Fungal strain of Pyrenophora teres - CPPF-453) grown in Petri dishes. Toxicity of PyrSMCs to Artemia salina was studied as well. Size of capsules was 200–600 nm along with the presence of bigger capsules with a diameter of 1–4 µm. PyrSMCs showed excellent antifungal effects above the melting point of octadecane. PyrSMCs demonstrated 29 times less toxicity than pyraclostrobin of technical grade. Overall, results show the potential of such capsules to be applied in the agricultural industry for precise agriculture strategies
Aurantoside K, a New Antifungal Tetramic Acid Glycoside from a Fijian Marine Sponge of the Genus Melophlus
No full textA new tetramic acid glycoside, aurantoside K, was isolated from a marine sponge belonging to the genus Melophlus. The structure of the compound was elucidated on the basis of spectroscopic analysis (1H NMR, 1H–1H COSY, HSQC, and HMBC, as well as high-resolution ESILCMS). Aurantoside K did not show any significant activity in antimalarial, antibacterial, or HCT-116 cytotoxicity assays, but exhibited a wide spectrum of antifungal activity against wild type Candida albicans, amphotericin-resistant C. albicans, Cryptococcus neoformans, Aspergillus niger, Penicillium sp., Rhizopus sporangia and Sordaria sp
Synthesis of antimalarial amide analogues based on the plant serrulatane diterpenoid 3,7,8-trihydroxyserrulat-14-en-19-oic acid
No full textA plant-derived natural product scaffold, 3,7,8-trihydroxyserrulat-14-en-19-oic acid (1) was isolated in high yield from the aerial parts of the endemic Australian desert plant Eremophila microtheca. This scaffold (1) was subsequently used in the generation of a series of new amide analogues via a one-pot mixed anhydride amidation using pivaloyl chloride. The structures of all analogues were characterized using MS, NMR, and UV data. The major serrulatane natural products (1–3), isolated from the plant extract, and all amide analogues (6–15) together with several pivaloylated derivatives of 3,7,8-trihydroxyserrulat-14-en-19-oic acid (16–18) were evaluated for their antimalarial activity against 3D7 (chloroquine sensitive) and Dd2 (chloroquine resistant) Plasmodium falciparum strains, and preliminary cytotoxicity data were also acquired using the human embryonic kidney cell line HEK293. The natural product scaffold (1) did not display any antimalarial activity at 10 µM. Replacing the carboxylic acid of 1 with various amides resulted in moderate activity against the P. falciparum 3D7 strain with IC50 values ranging from 1.25 to 5.65 µM.Griffith Sciences, Griffith Institute for Drug DiscoveryNo Full Tex
Synthesis of a Unique Psammaplysin F Library and Functional Evaluation in Prostate Cancer Cells by Multiparametric Quantitative Single Cell Imaging
No full textThe spirooxepinisoxazoline alkaloid psammaplysin F (1) was selected as a scaffold for the generation of a unique screening library for both drug discovery and chemical biology research. Large-scale extraction and isolation chemistry was performed on a marine sponge (Hyattella sp.) collected from the Great Barrier Reef in order to acquire >200 mg of the desired bromotyrosine-derived alkaloidal scaffold. Parallel solution-phase semisynthesis was employed to generate a series of psammaplysin-based urea (2–9) and amide analogues (10–11) in low to moderate yields. The chemical structures of all analogues were characterized using NMR and MS data. The absolute configuration of psammaplysin F and all semisynthetic analogues was determined as 6R, 7R by comparison of ECD data with literature values. All compounds (1–11) were evaluated for their effect on cell cycle distribution and changes to cancer metabolism in LNCaP prostate cancer cells using a multiparametric quantitative single-cell imaging approach. These investigations identified that in LNCaP cells psammaplysin F and some urea analogues caused loss of mitochondrial membrane potential, fragmentation of the mitochondrial tubular network, chromosome misalignment, and cell cycle arrest in mitosis.Full Tex
The use of isolated natural products as scaffolds for the generation of chemically diverse screening libraries for drug discovery
No full textA diverse range of strategies leading to natural product derived or inspired screening libraries aims to increase the number of new chemical entities emerging per year. However, the use of isolated natural products as scaffolds for the semi-synthesis of larger biological screening libraries remains rare. This particular method avoids the time-consuming and resource intensive de novo synthetic strategy for scaffold production, and has become more feasible through improvements to synthetic and isolation methodologies. This Highlight examines the increasing popularity of small- to large-sized screening libraries generated directly from isolated natural products. Several of the examples detailed herein show how this strategy can lead to improvements in not only potency but also other important (and often forgotten) drug discovery parameters such as toxicity, selectivity, lipophilicity and bioavailability. However, there are still improvements to be made to this method, particularly in the choice of the natural product scaffold and the derivatising reagents used. Avoidance of known nuisance compounds or structural alert motifs (e.g. PAINS) that interfere with bioactivity screens, and impact downstream drug development will play a significant role in the future success of this methodology. Incorporation of rational design strategies that take into account the physicochemical parameters (e.g. log P, MW, HBA, HBD) of the final semi-synthetic library analogues will also facilitate the discovery and development of leads and drugs. A multi-pronged approach to drug discovery that incorporates the use of isolated natural product scaffolds for library generation will surely be beneficial.Griffith Sciences, School of Natural SciencesFull Tex
Microthecaline A, a Quinoline Serrulatane Alkaloid from the Roots of the Australian Desert Plant Eremophila microtheca
No full textChemical investigation of the roots of the Australian desert plant Eremophila microtheca yielded microthecaline A (1), a novel quinoline–serrulatane natural product. The structure of 1 was determined by spectroscopic analysis, and the absolute configuration was assigned by ECD. Compound 1 exhibited moderate antimalarial activity against Plasmodium falciparum (3D7 strain), with an IC50 of 7.7 μM. Microthecaline A represents the first quinoline–serrulatane alkaloid to be isolated from Nature.Griffith Sciences, Griffith Institute for Drug DiscoveryNo Full Tex
Antimicrobial Activity of Extracts of Two Native Fruits of Chile: Arrayan (Luma apiculata) and Peumo (Cryptocarya alba)
No full textArrayan and peumo fruits are commonly used in the traditional medicine of Chile. In this study, the concentration of the extracts halving the bacterial viability and biofilms formation and disruption of the drug-sensitive and drug-resistant strains of Staphylococcus aureus and Pseudomonas aeruginosa was determined. The chemical composition of extracts was analyzed by high-resolution liquid chromatography coupled with mass spectrometry (U-HPLC/MS). The arrayan extract (Inhibitory concentration IC50 0.35 ± 0.01 mg/mL) was more effective than peumo extract (IC50 0.53 ± 0.02 mg/mL) in the inhibition of S. aureus planktonic cells. Similarly, the arrayan extract was more effective in inhibiting the adhesion (S. aureus IC50 0.23 ± 0.02 mg/mL, P. aeruginosa IC50 0.29 ± 0.02 mg/mL) than peumo extracts (S. aureus IC50 0.47 ± 0.03 mg/mL, P. aeruginosa IC50 0.35 ± 0.01 mg/mL). Both extracts inhibited quorum sensing in a concentration-dependent manner, and the most significant was the autoinducer-2 type communication inhibition by arrayan extract. Both extracts also disrupted preformed biofilm of P. aeruginosa (arrayan IC50 0.56 ± 0.04 mg/mL, peumo IC50 0.59 ± 0.04 mg/mL). However, neither arrayan nor peumo extracts disrupted S. aureus mature biofilm. U-HPLC/MS showed that both fruit extracts mainly possessed quercetin compounds; the peumo fruit extract also contained phenolic acids and phenylpropanoids. Our results suggested that both extracts could be used as natural antimicrobials for some skin and nosocomial infections
Microthecaline A, a Quinoline Serrulatane Alkaloid from the Roots of the Australian Desert Plant <i>Eremophila microtheca</i>
No full textChemical investigation of the roots
of the Australian desert plant Eremophila microtheca yielded microthecaline A (1), a novel quinoline–serrulatane
natural product. The structure
of 1 was determined by spectroscopic analysis, and the
absolute configuration was assigned by ECD. Compound 1 exhibited moderate antimalarial activity against Plasmodium
falciparum (3D7 strain), with an IC50 of 7.7 μM.
Microthecaline A represents the first quinoline–serrulatane
alkaloid to be isolated from Nature
