https://pubs.rsc.org/en/content/articlepdf/2019/NP/C8NP00092A

Marine natural products.

The chemical diversity and distribution of glucosinolates and isothiocyanates among plants

Aims: The minimum inhibitory concentration (MIC) of oregano essential oil (OEO) and two of its principle components, i.e. thymol and carvacrol, against Pseudomonas aeruginosa and Staphylococcus aureus was assessed by using an innovative technique. The mechanism of action of the above substances was also investigated. Methods and Results: The applied technique uses 100-well microtitre plate and collects turbidimetric growth data. To produce the inhibition profiles, a wide range of concentrations were tested for each of the three compounds, as well as for carvacrol‐thymol mixtures. Following a specific mathematical analysis of the observed inhibition profiles from all compounds, it was suggested that mixtures of carvacrol and thymol gave an additive effect and that the overall inhibition by OEO can be attributed mainly to the additive antimicrobial action of these two compounds. Addition of low amounts of each additive: (a) increased permeability of cells to the nuclear stain EB, (b) dissipated pH gradients as indicated by the CFDA-SE fluorescent probe irrespective of glucose availability and (c) caused leakage of inorganic ions. Conclusions: Mixing carvacrol and thymol at proper amounts may exert the total inhibition that is evident by oregano essential oil. Such inhibition is due to damage in membrane integrity, which further affects pH homeostasis and equilibrium of inorganic ions. Significance and Impact of the Study: The knowledge of extent and mode of inhibition of specific compounds, which are present in plant extracts, may contribute to the successful application of such natural preservatives in foods, since certain combinations of carvacrol‐ thymol provide as high inhibition as oregano essential oil with a smaller flavour impact.

/pdf/a-study-of-the-minimum-inhibitory-concentration-and-mode-of-brcmpgdh3k.pdf

A study of the minimum inhibitory concentration and mode of action of oregano essential oil, thymol and carvacrol.

http://webspace.pugetsound.edu/facultypages/bdasher/Chem361/Review_Articles_files/Drugs%20from%20Plants.pdf

Drug discovery from medicinal plants.

Due to the biological importances of thiols, such as cysteine, homocysteine and glutathione, the development of optical probes for thiols has been an active research area in recent few years. This critical review focuses on the fluorescent or colorimetric sensors for thiols according to their unique mechanisms between sensors and thiols, including Michael addition, cyclization with aldehyde, cleavage of sulfonamide and sulfonate ester by thiols, cleavage of selenium–nitrogen bond by thiols, cleavage of disulfide by thiols, metal complexes-oxidation–reduction, metal complexes-displace coordination, nano-particles and others (110 references).

Fluorescent and colorimetric probes for detection of thiols

Lightning Fast is a sensitive fluorescence-based stain for detecting proteins in one-dimensional and two-dimensional polyacrylamide electrophoresis gels. It contains the fluorophore epicocconone from the fungus Epicoccum nigrum that interacts noncovalently with sodium dodecyl sulfate and protein. Stained proteins can be excited optimally by near-ultraviolet light of about 395 nm or with visible light of about 520 nm. The stain can be excited using a range of sources used in image analysis systems including UVA (ca. 365 nm) and UVB (ca. 302 nm) transilluminators; Xenon-arc lamps; 488 nm and 457 nm Argon-ion lasers; 473 nm and 532 nm neodymium: yttrium aluminum garnet (Nd:YAG) solid-state lasers; 543 nm helium-neon lasers, and emerging violet, blue and green diode lasers. Maximum fluorescence emission of the dye is at approximately 610 nm. The limit of detection in one-dimensional gels stained with Lightning Fast protein gel stain is less than 100 pg of protein, rivaling the current limits of matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS). Lightning Fast was found to be considerably more sensitive than SYPRO Ruby, SYPRO Orange, silver and Coomassie Brilliant Blue G-250 in matched experiments. Staining takes as little as 3.5 h and stained proteins displayed quantitative linearity over more than four orders of magnitude, thereby allowing visualization of entire proteomes. Lightning Fast protein gel staining is compatible with subsequent peptide mass fingerprinting using MALDI-MS and Edman-based sequencing chemistry.

A fluorescent natural product for ultra sensitive detection of proteins in one-dimensional and two-dimensional gel electrophoresis

Epicocconone represents a new class of natural fluorescent probes based on a polyketide skeleton isolated from the fungus Epicoccum nigrum. Epicocconone is a small, cell permeable natural product with a high molar absorbtivity and a long Stokes' shift that will be useful in biotechnological applications.

Epicocconone, A Novel Fluorescent Compound from the Fungus Epicoccum nigrum

The fact that nudibranchs often contain interesting natural products has been known for over a decade. These natural products were quickly recognized as defensive agents usually sequestered from their particular prey. Recently more fundamental questions, requiring the close collaboration between chemists and biologists, have been addressed. These include the questions of chemoreception and chemosignalling of nuibranchs. The activities in this field are reviewed for the first time with particular emphasis on the defense mechanisms of nudibranchs and the chemical ecology of nudibranchs in all stages of their life cycle.

Chemical Ecology of the Nudibranchs

A spectrophotometric method has been developed for the rapid measurement of the antimicrobial activity of natural products, including crude extracts or pure materials. The assay depends on the measurement of non-specific esterase activity using fluorescein diacetate (FDA) hydrolysis in broth cultures of microbes after they have been treated with test compounds. The assay is accurate, reproducible and economical in both time and materials. The speed and economy of the method make it suitable for the rapid screening of many samples and the bioassay directed purification of antimicrobial substances. The assay can also be used with a wide variety of micro-organisms since most micro-organisms are FDA positive. Applications are described in the fields of marine natural products chemistry and essential oils research.

Rapid screening of the antimicrobial activity of extracts and natural products

Chemical genetics and reverse chemical genetics parallel classical genetics but target genes at the protein level and have proven useful in recent years for screening combinatorial libraries for compounds of biological interest. However, the performance of combinatorial chemistry in filling pharmaceutical pipelines has been lower than anticipated and the tide may be turning back to Nature in the search for new drug candidates. Even though diversity oriented synthesis is now producing molecules that are natural product-like in terms of size and complexity, these molecules have not evolved to interact with biomolecules. Natural products, on the other hand, have evolved to interact with biomolecules, which is why so many can be found in pharmacopoeias. However, the cellular targets and modes of action of these fascinating compounds are seldom known, hindering the drug development process. This review focuses on the emergence of chemical proteomics and reverse chemical proteomics as tools for the discovery of cellular receptors for natural products, thereby generating protein/ligand pairs that will prove useful in identifying new drug targets and new biologically active small molecule scaffolds. Such a system-wide approach to identifying new drugable targets and their small molecule ligands will help unblock the pharmaceutical product pipelines by speeding the process of target and lead identification.

Peter Karuso

Papers

A fluorescent natural product for ultra sensitive detection of proteins in one-dimensional and two-dimensional gel electrophoresis

Epicocconone, A Novel Fluorescent Compound from the Fungus Epicoccum nigrum

Chemical Ecology of the Nudibranchs

Rapid screening of the antimicrobial activity of extracts and natural products

Quality, not quantity: the role of natural products and chemical proteomics in modern drug discovery.