A unique high-diversity natural product collection as a reservoir of new therapeutic leads

Plants represent a rich source of structurally diverse secondary metabolites, which can be exploited in the development of new clinically important compounds. Indeed, due to their biodiversity, medicinal plants represent the largest library of compounds that has ever existed. To date less than 1% of this vast biodiversity has been exploited in drug discovery, due to several factors, including the lack of an appropriate multidisciplinary perspective. Here we review the successful application of computer-aided methods in screening a unique and high-diversity in house collection library composed of around 1000 individual natural products, isolated mainly from indigenous plants collected in biodiversity-rich countries, especially of the tropics and subtropics, and enlarged with their semi-synthetic and synthetic derivatives, as well as plant material extracts, up to around 2000 components. During the last ten years, the in house library has provided several lead compounds that have been developed, and in some cases patented, as anticancer and antimicrobial agents. The main classes of the library are described, including (but not limited to) alkaloids, terpenoids, Diels–Alder-type adducts, isoflavones, chalcones, and cannabinoids. The main focus is on the chemical characteristics and biological activity of these identified compounds, with particular attention being given to those currently under patent or in the preclinical phase. We also assess the use of computer-aided methods in screening this unique and diverse in house collection of natural products that, over the last ten years, has provided some lead compounds that have been developed, and in some cases patented, as anticancer and antimicrobial agents. Finally, this review highlights the potential use of plant food extracts as a source of nutraceuticals and functional foods. The multidisciplinary approach described herein may further motivate research groups involved in natural product chemistry to potentially benefit from a limitless source of novel bioactive compounds

A Multimethodological Characterization of Cannabis sativa L. Inflorescences from Seven Dioecious Cultivars Grown in Italy: The Effect of Different Harvesting Stages

The chemical profile of the female inflorescence extracts from seven Cannabis sativa L. dioecious cultivars (Carmagnola, Fibranova, Eletta Campana, Antal, Tiborszallasi, Kompolti, and Tisza) was monitored at three harvesting stages (4, 14, and 30 September), reaching from the be ginning of flowering to end of flowering/beginning of seed formation, using untargeted nuclear magnetic resonance (NMR) and targeted (ultra-high-performance liquid chromatography (UHPLC) and spectrophotometry) analyses. The tetrahydrocannabinol content was always below the legal limits (<0.6%) in all the analyzed samples. The NMR metabolite profile (sugars, organic acids, amino acids, and minor compounds) subjected to principal components analysis (PCA) showed a strong variability according to the harvesting stages: samples harvested in stage I were characterized by a high content of sucrose and myo-inositol, whereas the ones harvested in stage II showed high levels of succinic acid, alanine, valine, isoleucine, phenylalanine, and threonine. Samples harvested in stage III were characterized by high levels of glucose, fructose, choline, trigonelline, malic acid, formic acid, and some amino acids. The ratio between chlorophylls and carotenoids content indicated that all plants grew up exposed to the sun, the Eletta Campana cultivar having the highest pigment amount. Tiborszallasi cultivar showed the highest polyphenol content. The highest antioxidant activity was generally observed in stage II. All these results suggested that the Cannabis sativa L. inflorescences of each analyzed dioecious hemp cultivar presented a peculiar chemical profile affected by the harvesting stage. This information could be useful for producers and industries to harvest inflorescences in the appropriate stage to obtain samples with a peculiar chemical profile suitable for proper applications.15s

DEVELOPMENT OF ArnT-MEDIATED COLISTIN RESISTANCE DITERPENE-BASED INHIBITORS

Colistin is a last-line antibiotic for the treatment of multidrug resistant Gram-negative bacterial infections.1 Recently, a natural ent-beyerene diterpene (ent-Beyer-15-en-18-O-oxalate) was identified as a promising inhibitor of the enzyme responsible for colistin resistance mediated by lipid A aminoarabinosylation in Gram-negative bacteria, namely, ArnT (undecaprenyl phosphate-alpha-4-amino-4-deoxy-l-arabinose arabinosyl transferase).2 To explore the structure-activity relationship (SAR), semi-synthetic analogs of hit were designed, synthesized and tested against colistin-resistant Pseudomonas aeruginosa strains, including clinical isolates (figure 1), in order to exploit the versatility of the diterpene scaffold. Microbiological assays coupled with molecular modeling demonstrated that an ent-beyerane scaffold bearing an oxalate like group at C-18/C-19, or a sugar residue at C-19 to resemble L-Ara4N is an essential requirement for a more efficient inhibition of bacterial growth likely resulting from a more efficient inhibition of ArnT activity. Importantly, the easy accessibility of ent-beyerane scaffold from Stevia rebaudiana secondary metabolites will provide a cost-effective key platform for the development of promising colistin resistance inhibitors

Resorc[4]arene-functionalized MWCNTS for the development of new highly sensitive immunosensors

One of the main problems in the development of immunosensors is to overcome the complexity of binding antibodies onto the sensor surface, thus leading to a loss of sensitivity.[1] For this reason, in the last twenty years, macrocyclic species such as calix[4]arene has been used for the site-directed immobilization of antibodies in the correct end-on orientation.[2] In the last years, due to their configuration and unique molecular recognition properties, resorcinol-based cyclooligomes, namely resorc[4]arenes,[3] have been used for the development of highly sensitive immunosensors.[4] In this project, new resorc[4]arene-based derivatives have been designed and synthesized for covalent grafting by nucleophilic substitution or cycloaddition of multi-walled carbon nanotubes, a versatile material endowed with great electric properties, high electroactive surface area and biocompatibility.[5] The prepared materials have been fully characterized by both morphological (FE-SEM and AFM) and spectroscopical (XPS) techniques before the construction of the immunosensors. Finally, the modified electrodes have been characterized by DPV and CV and IgG antibodies for the SARS-CoV-2 spike protein S1 (SPS1) were immobilized on their surface. The developed immunodevice was then employed in the analysis of SPS1 standard solutions as a proof of concept for COVID-19 immunosensor

Identification of small molecular chaperones binding p23h mutant opsin through an in silico structure-based approach

N-terminal P23H opsin mutation accounts for most of retinitis pigmentosa (RP) cases. P23H functions and folding can be rescued by small chaperone ligands, which contributes to validate mutant opsin as a suitable target for pharmacological treatment of RP. However, the lack of structural details on P23H mutant opsin strongly impairs drug design, and new chemotypes of effective chaperones of P23H opsin are in high demand. Here, a computational-boosted workflow combining homology modeling with molecular dynamics (MD) simulations and virtual screening was used to select putative P23H opsin chaperones among different libraries through a structure-based approach. In vitro studies corroborated the reliability of the structural model generated in this work and identified a number of novel chemotypes of safe and effective chaperones able to promote P23H opsin trafficking to the outer cell membrane

Resorc[4]arene-functionalized MWCNTs for the development of new highly sensitive electrochemical immunosensors

One of the main problems in the development of immunosensors is to overcome the complexity of binding antibodies (Abs) onto the sensor surface, thus leading to a loss of sensitivity. 1 In the last twenty years, preorganized macrocycles, i.e. calixarenes, were employed for the site-directed immobilization of Abs to promote the correct end-on orientation. 2 Recently, due to their configuration and unique molecular recognition properties, resorcinol-based cyclooligomes, namely resorcarenes, 3 turned out to be a good option for the construction of highly sensitive immunosensors. 4 In this project, resorc[4]arene architectures decorated with eight methoxy groups at the upper rim and substituted at the lower rim with different functional groups (i.e., 3-bromopropyloxy and 3-azidopropiloxy substituents) were rationally designed and synthesized to tailor their recognition properties towards the Fc portion of Abs and to covalently install the artificial linkers on the multi-walled carbon nanotubes (MWCNTs) surface. Different chemical methods including nucleophilic substitution, click chemistry, or direct cycloaddition via nitrene were exploited. The MWCNTs modified with the resorc[4]arenes were morphologically and electronically characterized by field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and X-ray photoemission spectroscopy (XPS) before the fabrication of modified electrodes. The latter were electrochemically characterized, and IgG Abs for the SARS-CoV-2 spike protein S1 (SPS1) were immobilized on their surface. The well-designed resorc[4]arene-functionalized MWCNTs-based immunosensors emerged as powerful systems for the development of more efficient immunosensing devices

The revaluation of plant-derived terpenes to fight antibiotic-resistant Infections

The discovery of antibiotics has revolutionized the medicine and treatment of microbial infections. However, the current scenario has highlighted the difficulties in marketing new antibiotics and an exponential increase in the appearance of resistant strains. On the other hand, research in the field of drug-discovery has revaluated the potential of natural products as a unique source for new biologically active molecules and scaffolds for the medicinal chemistry. In this review, we first contextualized the worldwide problem of antibiotic resistance and the importance that natural products of plant origin acquire as a source of new lead compounds. We then focused on terpenes and their potential development as antimicrobials, highlighting those studies that showed an activity against conventional antibiotic-resistant strains

ent-Beyerane Diterpenes as a Key Platform for the Development of ArnT-Mediated Colistin Resistance Inhibitors

Colistin is a last-resort antibiotic for the treatment of multidrug resistant Gram-negative bacterial infections. Recently, a natural ent-beyerene diterpene was identified as a promising inhibitor of the enzyme responsible for colistin resistance mediated by lipid A aminoarabinosylation in Gram-negative bacteria, namely, ArnT (undecaprenyl phosphate-alpha-4-amino-4-deoxy-L-arabinose arabinosyl transferase). Here, semisynthetic analogues of hit were designed, synthetized, and tested against colistin-resistant Pseudomonas aeruginosa strains including clinical isolates to exploit the versatility of the diterpene scaffold. Microbiological assays coupled with molecular modeling indicated that for a more efficient colistin adjuvant activity, likely resulting from inhibition of the ArnT activity by the selected compounds and therefore from their interaction with the catalytic site of ArnT, an ent-beyerane scaffold is required along with an oxalate-like group at C-18/C-19 or a sugar residue at C-19 to resemble L-Ara4N. The ent-beyerane skeleton is identified for the first time as a privileged scaffold for further cost-effective development of valuable colistin resistance inhibitors.Istituto Pasteur Italia Fondazione Cenci Bolognetti Ministry of Health, Italy Italian Cystic Fibrosis Research Foundation 15/2019 Excellence Departments grant from MIUR commi 314-337 Legge 232/2016 Departments of Chemistry and Technology of Drugs of the Sapienza University of Rome Department of Biotechnology, Chemistry and Pharmacy of the University of Siena PON (Piano Operativo Nazionale) ARS01_00432 03/2018-09/2020 Ministry of Education, Universities and Research (MIUR) Research Projects of National Relevance (PRIN) Sapienza University RM11816436113D8A European Cooperation in Science and Technology (COST) CM140

Resorc[4]arene-functionalized MWCNTs for the development of new highly sensitive electrochemical immunosensors

One of the main problems in the development of immunosensors is to overcome the complexity of binding antibodies (Abs) onto the sensor surface, thus leading to a loss of sensitivity. 1 In the last twenty years, preorganized macrocycles, i.e. calixarenes, were employed for the site-directed immobilization of Abs to promote the correct end-on orientation. 2 Recently, due to their configuration and unique molecular recognition properties, resorcinol-based cyclooligomes, namely resorcarenes, 3 turned out to be a good option for the construction of highly sensitive immunosensors. 4 In this project, resorc[4]arene architectures decorated with eight methoxy groups at the upper rim and substituted at the lower rim with different functional groups (i.e., 3-bromopropyloxy and 3-azidopropiloxy substituents) were rationally designed and synthesized to tailor their recognition properties towards the Fc portion of Abs and to covalently install the artificial linkers on the multi-walled carbon nanotubes (MWCNTs) surface. Different chemical methods including nucleophilic substitution, click chemistry, or direct cycloaddition via nitrene were exploited. The MWCNTs modified with the resorc[4]arenes were morphologically and electronically characterized by field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and X-ray photoemission spectroscopy (XPS) before the fabrication of modified electrodes. The latter were electrochemically characterized, and IgG Abs for the SARS-CoV-2 spike protein S1 (SPS1) were immobilized on their surface. The well-designed resorc[4]arene-functionalized MWCNTs-based immunosensors emerged as powerful systems for the development of more efficient immunosensing devices

Identification of Effective Anticancer G-Quadruplex-Targeting Chemotypes through the Exploration of a High Diversity Library of Natural Compounds

In the quest for selective G-quadruplex (G4)-targeting chemotypes, natural compounds have been thus far poorly explored, though representing appealing candidates due to the high structural diversity of their scaffolds. In this regard, a unique high diversity in-house library composed of ca. one thousand individual natural products was investigated. The combination of molecular docking-based virtual screening and the G4-CPG experimental screening assay proved to be useful to quickly and effectively identify—out of many natural compounds—five hit binders of telomeric and oncogenic G4s, i.e., Bulbocapnine, Chelidonine, Ibogaine, Rotenone and Vomicine. Biophysical studies unambiguously demonstrated the selective interaction of these compounds with G4s compared to duplex DNA. The rationale behind the G4 selective recognition was suggested by molecular dynamics simulations. Indeed, the selected ligands proved to specifically interact with G4 structures due to peculiar interaction patterns, while they were unable to firmly bind to a DNA duplex. From biological assays, Chelidonine and Rotenone emerged as the most active compounds of the series against cancer cells, also showing good selectivity over normal cells. Notably, the anticancer activity correlated well with the ability of the two compounds to target telomeric G4s