Natural products isolation in modern drug discovery programs

Plant‐Based Natural Bioactive Compounds 2,4‐Ditert‐Butylphenolas: A Potential Candidates Against SARS‐Cov‐2019

The novel coronavirus 2019 is spreading around the world and causing serious concern. However, there is limited information about novel coronavirus that hinders the design of effective drug. Bioactive compounds are rich source of chemo preventive ingredients. In our present research focuses on identifying and recognizing bioactive chemicals in Lantana camara, by evaluating their potential toward new coronaviruses and confirming the findings using molecular docking, ADMET, network analysis and dynamics investigations.. The spike protein receptor binding domain were docked with 25 identified compounds and 2,4-Ditertbutyl-phenol (-6.3kcal/mol) shows highest docking score, its interactions enhances the increase in binding and helps to identify the biological activity. The ADME/toxicity result shows that all the tested compounds can serve as inhibitors of the enzymes CYP1A2 and CYP2D6. In addition, Molecular dynamics simulations studies with reference inhibitors were carried out to test the stability. This study identifies the possible active molecules against the receptor binding domain of spike protein, which can be further exploited for the treatment of novel coronavirus 2019. The results of the toxicity risk for phytocompounds and their active derivatives showed a moderate to good drug score.

Construction and Screening of Fractional Library of Salviae Miltiorrhizae Radix et Rhizoma for the Rapid Identification of Active Compounds against Prostate Cancer

Efficient screening of anticancer agents is in urgent need to develop new drugs that combat malignant tumors and drug resistance. In this study, a combined strategy composed by solvent partition and HPLC fractionation was developed to generate an herbal fraction library of Salviae Miltiorrhizae Radix et Rhizoma to quickly and efficiently screen anticancer agents. All library entries are directed into 96 well plates which are well mapped with HPLC chromatograms. The cell proliferation assay revealed seven active subfractions. Then, the major active ten peaks in these subfractions were prepared and isolated by semipreparative HPLC, and their inhibitory activities against prostate cancer cells were then tested at the same concentration level, leading to the identification of several active compounds. In addition, the structures of compounds arucadiol (2), 15,16-dihydrotanshinone I (4), methyl tanshinonate (5), cryptanshinone (7), 1,2-dihydrotanshinquinone I (9), and tanshinone IIA (10) were characterized by mass spectrometry and X-ray crystallographic analysis, and they were confirmed to be active in suppressing prostate cancer cell proliferation at 7.5 or 15 μg/mL, among which, the minor compounds 2, 4, and 5 showed higher activities than 9 and 10. This study provided a rapid strategy of identifying new anticancer agents in Salviae Miltiorrhizae Radix et Rhizoma, which can be applied in other herbal medicines.

Teucrium polium: Potential Drug Source for Type 2 Diabetes Mellitus

Simple Summary

Teucrium polium (also known as Golden Germander) is a herb brewed and drunk as a tea by the locals of the Mediterranean region, used mostly to treat a number of illnesses including diabetes. When consumed regularly, the tea can be problematic since some of its ingredients can be toxic or interfere with other medications taken by the patient. Current anti-diabetic medications are not always suitable nor optimal for all patients living with diabetes and therefore new drugs are constantly being sought after which may be more useful and/or present less side effects. Therefore, identifying the specific constituents that give the desired anti-diabetic effect, isolating them and developing them further may provide new useful anti-diabetic drugs. This paper discusses some key compounds found in Golden Germander that might be valuable for developing a new medication for type 2 diabetics whilst outlining some issues with the research conducted thus far.

Abstract

The prevalence of type 2 diabetes mellitus is rising globally and this disease is proposed to be the next pandemic after COVID-19. Although the cause of type 2 diabetes mellitus is unknown, it is believed to involve a complex array of genetic defects that affect metabolic pathways which eventually lead to hyperglycaemia. This hyperglycaemia arises from an inability of the insulin-sensitive cells to sufficiently respond to the secreted insulin, which eventually results in the inadequate secretion of insulin from pancreatic β-cells. Several treatments, utilising a variety of mechanisms, are available for type 2 diabetes mellitus. However, more medications are needed to assist with the optimal management of the different stages of the disease in patients of varying ages with the diverse combinations of other medications co-administered. Throughout modern history, some lead constituents from ancient medicinal plants have been investigated extensively and helped in developing synthetic antidiabetic drugs, such as metformin. Teucrium polium L. (Tp) is a herb that has a folk reputation for its antidiabetic potential. Previous studies indicate that Tp extracts significantly decrease blood glucose levels r and induce insulin secretion from pancreatic β-cells in vitro. Nonetheless, the constituent/s responsible for this action have not yet been elucidated. The effects appear to be, at least in part, attributable to the presence of selected flavonoids (apigenin, quercetin, and rutin). This review aims to examine the reported glucose-lowering effect of the herb, with a keen focus on insulin secretion, specifically related to type 2 diabetes mellitus. An analysis of the contribution of the key constituent flavonoids of Tp extracts will also be discussed.

Modern Approaches in the Discovery and Development of Plant-Based Natural Products and Their Analogues as Potential Therapeutic Agents

Natural products represents an important source of new lead compounds in drug discovery research. Several drugs currently used as therapeutic agents have been developed from natural sources; plant sources are specifically important. In the past few decades, pharmaceutical companies demonstrated insignificant attention towards natural product drug discovery, mainly due to its intrinsic complexity. Recently, technological advancements greatly helped to address the challenges and resulted in the revived scientific interest in drug discovery from natural sources. This review provides a comprehensive overview of various approaches used in the selection, authentication, extraction/isolation, biological screening, and analogue development through the application of modern drug-development principles of plant-based natural products. Main focus is given to the bioactivity-guided fractionation approach along with associated challenges and major advancements. A brief outline of historical development in natural product drug discovery and a snapshot of the prominent natural drugs developed in the last few decades are also presented. The researcher’s opinions indicated that an integrated interdisciplinary approach utilizing technological advances is necessary for the successful development of natural products. These involve the application of efficient selection method, well-designed extraction/isolation procedure, advanced structure elucidation techniques, and bioassays with a high-throughput capacity to establish druggability and patentability of phyto-compounds. A number of modern approaches including molecular modeling, virtual screening, natural product library, and database mining are being used for improving natural product drug discovery research. Renewed scientific interest and recent research trends in natural product drug discovery clearly indicated that natural products will play important role in the future development of new therapeutic drugs and it is also anticipated that efficient application of new approaches will further improve the drug discovery campaign.

The isolation of water-soluble natural products - challenges, strategies and perspectives

Covering period: up to 2019Water-soluble natural products constitute a relevant group of secondary metabolites notably known for presenting potent biological activities. Examples are aminoglycosides, β-lactam antibiotics, saponins of both terrestrial and marine origin, and marine toxins. Although extensively investigated in the past, particularly during the golden age of antibiotics, hydrophilic fractions have been less scrutinized during the last few decades. This review addresses the possible reasons on why water-soluble metabolites are now under investigated and describes approaches and strategies for the isolation of these natural compounds. It presents examples of several classes of hydrosoluble natural products and how they have been isolated. Novel stationary phases and chromatography techniques are also reviewed, providing a perspective towards a renaissance in the investigation of water-soluble natural products.

The Strong Anti-Kinetoplastid Properties of Bee Propolis: Composition and Identification of the Active Agents and Their Biochemical Targets

The kinetoplastids are protozoa characterized by the presence of a distinctive organelle, called the kinetoplast, which contains a large amount of DNA (kinetoplast DNA (kDNA)) inside their single mitochondrion. Kinetoplastids of medical and veterinary importance include Trypanosoma spp. (the causative agents of human and animal African Trypanosomiasis and of Chagas disease) and Leishmania spp. (the causative agents of the various forms of leishmaniasis). These neglected diseases affect millions of people across the globe, but drug treatment is hampered by the challenges of toxicity and drug resistance, among others. Propolis (a natural product made by bees) and compounds isolated from it are now being investigated as novel treatments of kinetoplastid infections. The anti-kinetoplastid efficacy of propolis is probably a consequence of its reported activity against kinetoplastid parasites of bees. This article presents a review of the reported anti-kinetoplastid potential of propolis, highlighting its anti-kinetoplastid activity in vitro and in vivo regardless of geographical origin. The mode of action of propolis depends on the organism it is acting on and includes growth inhibition, immunomodulation, macrophage activation, perturbation of the cell membrane architecture, phospholipid disturbances, and mitochondrial targets. This gives ample scope for further investigations toward the rational development of sustainable anti-kinetoplastid drugs.

N-Acetyl-l-cysteine/l-Cysteine-Functionalized Chitosan-β-Lactoglobulin Self-Assembly Nanoparticles: A Promising Way for Oral Delivery of Hydrophilic and Hydrophobic Bioactive Compounds

Self-assembled and cross-linked hybrid hydrogels for entrapment and delivery of hydrophilic and hydrophobic bioactive compounds were developed based on N-acetyl-l-cysteine (NAC)- or l-cysteine (CYS)-functionalized chitosan-β-lactoglobulin nanoparticles (NPs). In both the systems, amphiphilic protein β-lactoglobulin (β-lg) was self-assembled by using glutaraldehyde for affinity binding with egg white-derived peptides (EWDP) and curcumin and then coated with NAC- or CYS-functionalized chitosan (CS) by electrostatic interaction. The resulting NPs were characterized in terms of size, polydispersity, and surface charge by dynamic light scattering. Results corroborated pH-sensitive properties of NAC-CS-β-lg NPs and CYS-CS-β-lg NPs with the particle size as small as 118 and 48 nm, respectively. The two kinds of NPs also showed excellent entrapment of EWDP and curcumin with the entrapment efficiency (EE) of EWDP and curcumin ranging from 51 to 89% and 42 to 57% in NAC-CS-β-lg NPs, as well as 50-81% and 41-57% in CYS-CS-β-lg NPs under different pH values. Fourier transform infrared and molecular docking studies provided support for the interaction mechanism of NAC/CYS-CS with β-lg as well as the NPs with EWDP and curcumin. Strikingly, the in vitro release kinetics of EWDP and curcumin exhibited the controlled and sustained release properties up to 58 and 70 h from the NPs, respectively. Note that the permeability of QIGLF (pentapeptide, isolated from EWDP) and curcumin passing through Caco-2 cell monolayers were all improved after the entrapment in the NPs. This work offers promising methods for effective entrapment and oral delivery of both hydrophilic and hydrophobic bioactive compounds.

Impact of Six Typical Processing Methods on the Chemical Composition of Tea Leaves Using a Single Camellia sinensis Cultivar, Longjing 43

While the Camellia sinensis cultivar and processing method are key factors that affect tea flavor and aroma, the chemical changes in nonvolatile components associated with the tea processing method using a single cultivar of C. sinensis have not been reported. Fresh leaves from C. sinensis Longjing 43 were subjected to six tea processing methods and evaluated by targeted and untargeted chromatographic procedures. On the basis of targeted assessment of the total catechin content, three clusters were identified: yellow-green, oolong-white-dark, and black. However, principal component analysis of the total tea metabolome identified four chemical phenotypes: green-yellow, oolong, black-white, and dark. Differences in the non-catechin components included amino acids and γ-aminobutyric acid, which increased in white tea, and dihydroxyphenylalanine, valine, betaine, and theophylline, which increased in dark tea. Overall, this study identified a wide range of chemicals that are affected by commonly used tea processing methods and potentially affect the bioactivity of various tea types.

Investigations to the Antibacterial Mechanism of Action of Kendomycin

Purpose

The emergence of bacteria that are resistant to many currently used drugs emphasizes the need to discover and develop new antibiotics that are effective against such multi-resistant strains. Kendomycin is a novel polyketide that has a unique quinone methide ansa structure and various biological properties. This compound exhibits strong antibacterial activity against Gram-negative and Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). Despite the promise of kendomycinin in several therapeutic areas, its mode of action has yet to be identified.

Methods

In this study, we used a multidisciplinary approach to gain insight into the antibacterial mechanism of this compound.

Results

The antibacterial activity of kendomycin appears to be bacteriostatic rather than bactericidal. Kendomycin inhibited the growth of the MRSA strain COL at a low concentration (MIC of 5 μg/mL). Proteomic analysis and gene transcription profiling of kendomycin-treated cells indicated that this compound affected the regulation of numerous proteins and genes involved in central metabolic pathways, such as the tricarboxylic acid (TCA) cycle (SdhA) and gluconeogenesis (PckA and GapB), cell wall biosynthesis and cell division (FtsA, FtsZ, and MurAA), capsule production (Cap5A and Cap5C), bacterial programmed cell death (LrgA and CidA), the cellular stress response (ClpB, ClpC, ClpP, GroEL, DnaK, and GrpE), and oxidative stress (AhpC and KatA). Electron microscopy revealed that kendomycin strongly affected septum formation during cell division. Most kendomycin-treated cells displayed incomplete septa with abnormal morphology.

Conclusions

Kendomycin might directly or indirectly affect the cell division machinery, protein stability, and programmed cell death in S. aureus. Additional studies are still needed to obtain deeper insight into the mode of action of kendomycin.

The re-emergence of natural products for drug discovery in the genomics era

Natural products have been a rich source of compounds for drug discovery. However, their use has diminished in the past two decades, in part because of technical barriers to screening natural products in high-throughput assays against molecular targets. Here, we review strategies for natural product screening that harness the recent technical advances that have reduced these barriers. We also assess the use of genomic and metabolomic approaches to augment traditional methods of studying natural products, and highlight recent examples of natural products in antimicrobial drug discovery and as inhibitors of protein-protein interactions. The growing appreciation of functional assays and phenotypic screens may further contribute to a revival of interest in natural products for drug discovery.

Biodiversity in production of antibiotics and other bioactive compounds

Microbes continue to play a highly considerable role in the drug discovery and development process. Nevertheless, the number of new chemical entities (NCEs) of microbial origin that has been approved by the Food and Drug Administration (FDA) has been reduced in the past decade. This scarcity can be partly attributed to the redundancy in the discovered molecules from microbial isolates, which are isolated from common terrestrial ecological units. However, this situation can be partly overcome by exploring rarely exploited ecological niches as the source of microbes, which reduces the chances of isolating compounds similar to existing ones. The use of modern and advanced isolation techniques, modification of the existing fermentation methods, genetic modifications to induce expression of silent genes, analytical tools for the detection and identification of new chemical entities, use of polymers in fermentation to enhance yield of fermented compounds, and so on, have all aided in enhancing the frequency of acquiring novel compounds. These compounds are representative of numerous classes of diverse compounds. Thus, compounds of microbial origin and their analogues undergoing clinical trials continue to demonstrate the importance of compounds from microbial sources in modern drug discovery.

Venus Flytrap (Dionaea muscipula Solander ex Ellis) Contains Powerful Compounds that Prevent and Cure Cancer

Chemoprevention uses natural or synthetic molecules without toxic effects to prevent and/or block emergence and development of diseases including cancer. Many of these natural molecules modulate mitogenic signals involved in cell survival, apoptosis, cell cycle regulation, angiogenesis, or on processes involved in the development of metastases occur naturally, especially in fruits and vegetables bur also in non-comestible plants. Carnivorous plants including the Venus flytrap (Dionaea muscipula Solander ex Ellis) are much less investigated, but appear to contain a wealth of potent bioactive secondary metabolites. Aim of this review is to give insight into molecular mechanisms triggered by compounds isolated from these interesting plants with either therapeutic or chemopreventive potential.

Xiao-Ai-Ping, a TCM Injection, Enhances the Antigrowth Effects of Cisplatin on Lewis Lung Cancer Cells through Promoting the Infiltration and Function of CD8(+) T Lymphocytes

Objectives. To investigate how Xiao-Ai-Ping injection, a traditional Chinese medicine and an ancillary drug in tumor treatment, enhances the antitumor effects of cisplatin on Lewis lung cancer (LLC) cells. Methods. LLC-bearing mice were daily intraperitoneally injected with various doses of cisplatin, Xiao-Ai-Ping, or cisplatin plus Xiao-Ai-Ping, respectively. Body weight and tumor volumes were measured every three days. Results. Combination of Xiao-Ai-Ping and cisplatin yielded significantly better antigrowth and proapoptotic effects on LLC xenografts than sole drug treatment did. In addition, we found that Xiao-Ai-Ping triggered the infiltration of CD8⁺ T cells, a group of cytotoxic T cells, to LLC xenografts. Furthermore, the mRNA levels of interferon-γ (ifn-γ), perforin-1 (prf-1), and granzyme B (gzmb) in CD8⁺ T cells were significantly increased after combination treatment of Xiao-Ai-Ping and cisplatin. In vitro studies showed that Xiao-Ai-Ping markedly upregulated the mRNA levels of ifn-γ, prf-1, and gzmb in CD8⁺ T cells in a concentration-dependent manner, suggesting that Xiao-Ai-Ping augments the function of CD8⁺ T cells. Conclusions. Xiao-Ai-Ping promotes the infiltration and function of CD8⁺ T cells and thus enhances the antigrowth effects of cisplatin on LLC xenografts, which provides new evidence for the combination of Xiao-Ai-Ping and cisplatin in clinic in China.

Astragaloside IV suppresses collagen production of activated hepatic stellate cells via oxidative stress-mediated p38 MAPK pathway

Oxidative stress is involved in hepatic fibrogenesis. Activation of hepatic stellate cells (HSCs), the key effectors in hepatic fibrogenesis, is characterized by overproduction of extracellular matrix. Astragaloside IV, the active component of Radix Astragali, has antioxidant properties and antifibrotic potential in renal fibrosis. Little is known about the role of astragaloside IV in liver and its involvement in hepatic fibrosis. This study aims at evaluating the antifibrotic potential of astragaloside IV and characterizing involved signal transduction pathways in culture-activated HSCs. Our results show that astragaloside IV attenuates oxidative stress in culture-activated HSCs, as demonstrated by scavenging reactive oxygen species and reducing lipid peroxidation, and elevates the level of cellular glutathione by stimulating Nrf2gene expression. Depletion of cellular glutathione by buthionine sulfoximine or abrogation of p38 MAPK by SB-203580 evidently eliminates the inhibitory effects of astragaloside IV on genes relevant to HSC activation. These results demonstrate that astragaloside IV inhibits HSC activation by inhibiting generation of oxidative stress and associated p38 MAPK activation and provide novel insights into the mechanisms of astragaloside IV as an antifibrogenic candidate in the prevention and treatment of liver fibrosis.

Metabolomics and dereplication strategies in natural products

Metabolomic methods can be utilized to screen diverse biological sources of potentially novel and sustainable sources of antibiotics and pharmacologically-active drugs. Dereplication studies by high resolution Fourier transform mass spectrometry coupled to liquid chromatography (LC-HRFTMS) and nuclear magnetic resonance (NMR) spectroscopy can establish the chemical profile of endophytic and/or endozoic microbial extracts and their plant or animal sources. Identifying the compounds of interest at an early stage will aid in the isolation of the bioactive components. Therefore metabolite profiling is important for functional genomics and in the search for new pharmacologically active compounds. Using the tools of metabolomics through the employment of LC-HRFTMS as well as high resolution NMR will be a very efficient approach. Metabolomic profiling has found its application in screening extracts of macroorganisms as well as in the isolation and cultivation of suspected microbial producers of bioactive natural products.Metabolomics is being applied to identify and biotechnologically optimize the production of pharmacologically active secondary metabolites. The links between metabolome evolution during optimization and processing factors can be identified through metabolomics. Information obtained from a metabolomics dataset can efficiently establish cultivation and production processes at a small scale which will be finally scaled up to a fermenter system, while maintaining or enhancing synthesis of the desired compounds. MZmine (BMC Bioinformatics 11:395-399, 2010; http://mzmine.sourceforge.net/download.shtml ) and SIEVE ( http://www.vastscientific.com/resources/index.html ; Rapid Commun Mass Spectrom 22:1912-1918, 2008) softwares are utilized to perform differential analysis of sample populations to find significant expressed features of complex biomarkers between parameter variables. Metabolomes are identified with the aid of existing high resolution MS and NMR records from online or in-house databases like AntiMarin, a merger database of Antibase (Laatsch H. Antibase Version 4.0 - The Natural Compound Identifier. Wiley-VCH Verlag GmbH & Co. KGaA, 2012) for microbial secondary metabolites as well as higher fungi and MarinLit for marine natural products (Blunt J. MarinLit. University of Canterbury, New Zealand, 2012). This is further validated through available reference standards and NMR experiments. Metabolomics has become a powerful tool in systems biology which allows us to gain insights into the potential of natural isolates for synthesis of significant quantities of promising new agents and allows us to manipulate the environment within fermentation systems in a rational manner to select a desired metabolome.

Docking studies and network analyses reveal capacity of compounds from Kandelia rheedii to strengthen cellular immunity by interacting with host proteins during tuberculosis infection

Kandelia rheedii (locally known as Guria or Rasunia), widely found and used in Indian subcontinent, is a well-known herbal cure to tuberculosis. However, neither the mechanism nor the active components of the plant extract responsible for mediating this action has yet been confirmed. Here in this study, molecular interactions of three compounds (emodin, fusaric acid and skyrin) from the plant extract with the host protein targets (casein kinase (CSNK), estrogen receptor (ERBB), dopamine β-hydroxylase (DBH) and glucagon receptor (Gcgr)) has been found. These protein targets are known to be responsible for strengthening cellular immunity against Mycobacteria tuberculosis. The specific interactions of these three compounds with the respective protein targets have been discussed here. The insights from study should further help us designing molecular medicines against tuberculosis.