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The knowledge that natural products (NPs) are potent and selective modulators of important biomacromolecules (e.g., DNA and proteins) has inspired some of the world's most successful pharmaceuticals and agrochemicals. Notwithstanding these successes and despite a growing number of reports on naturally occurring pairs of enantiomers, this area of NP science still remains largely unexplored, consistent with the adage "If you don't seek, you don't find". Statistically, a rapidly growing number of enantiomeric NPs have been reported in the last several years. The current review provides a comprehensive overview of recent records on natural enantiomers, with the aim of advancing awareness and providing a better understanding of the chemical diversity and biogenetic context, as well as the biological properties and therapeutic (drug discovery) potential, of enantiomeric NPs.

Plant secondary metabolites (PSMs) are vital for human health and constitute the skeletal framework of many pharmaceutical drugs. Indeed, more than 25% of the existing drugs belong to PSMs. One of the continuing challenges for drug discovery and pharmaceutical industries is gaining access to natural products, including medicinal plants. This bottleneck is heightened for endangered species prohibited for large sample collection, even if they show biological hits. While cultivating the pharmaceutically interesting plant species may be a solution, it is not always possible to grow the organism outside its natural habitat. Plants affected by abiotic stress present a potential alternative source for drug discovery. In order to overcome abiotic environmental stressors, plants may mount a defense response by producing a diversity of PSMs to avoid cells and tissue damage. Plants either synthesize new chemicals or increase the concentration (in most instances) of existing chemicals, including the prominent bioactive lead compounds morphine, camptothecin, catharanthine, epicatechin-3-gallate (EGCG), quercetin, resveratrol, and kaempferol. Most PSMs produced under various abiotic stress conditions are plant defense chemicals and are functionally anti-inflammatory and antioxidative. The major PSM groups are terpenoids, followed by alkaloids and phenolic compounds. We have searched the literature on plants affected by abiotic stress (primarily studied in the simulated growth conditions) and their PSMs (including pharmacological activities) from PubMed, Scopus, MEDLINE Ovid, Google Scholar, Databases, and journal websites. We used search keywords: "stress-affected plants," "plant secondary metabolites, "abiotic stress," "climatic influence," "pharmacological activities," "bioactive compounds," "drug discovery," and "medicinal plants" and retrieved published literature between 1973 to 2021. This review provides an overview of variation in bioactive phytochemical production in plants under various abiotic stress and their potential in the biodiscovery of therapeutic drugs. We excluded studies on the effects of biotic stress on PSMs.

Introduction: Protein kinase C (PKC) is a promising drug target for various therapeutic areas. Natural products derived from plants, animals, microorganisms, and marine organisms have been used by humans as medicine from prehistoric times. Recently, several compounds derived from plants have been found to modulate PKC activities through competitive binding with ATP binding site, and other allosteric regions of PKC. As a result fresh race has been started in academia and pharmaceutical companies to develop an effective naturally derived small-molecule inhibitor to target PKC activities. Herein, in this review, we have discussed several natural products and their derivatives, which are reported to have an impact on PKC signaling cascade., Methods: All information presented in this review article regarding the regulation of PKC by natural products has been acquired by a systematic search of various electronic databases, including ScienceDirect, Scopus, Google Scholar, Web of science, ResearchGate, and PubMed. The keywords PKC, natural products, curcumin, rottlerin, quercetin, ellagic acid, epigallocatechin-3 gallate, ingenol 3 angelate, resveratrol, protocatechuic acid, tannic acid, PKC modulators from marine organism, bryostatin, staurosporine, midostaurin, sangivamycin, and other relevant key words were explored., Results: The natural products and their derivatives including curcumin, rottlerin, quercetin, ellagic acid, epigallocatechin-3 gallate, ingenol 3 angelate, resveratrol, bryostatin, staurosporine, and midostaurin play a major role in the management of PKC activity during various disease progression., Conclusion: Based on the comprehensive literature survey, it could be concluded that various natural products can regulate PKC activity during disease progression. However, extensive research is needed to circumvent the challenge of isoform specific regulation of PKC by natural products., (© 2021. Springer Nature Switzerland AG.)

In continuation of phytochemical investigations of the methanolic extract of Dictyopteris hoytii, we have obtained twelve compounds ( 1 - 12 ) through column chromatography. Herein, three compounds, namely, dimethyl 2-bromoterepthalate ( 3 ), dimethyl 2,6-dibromoterepthalate ( 4 ), and ( E )-3-(4-(dimethoxymethyl)phenyl) acrylic acid ( 5 ) are isolated for the first time as a natural product, while the rest of the compounds ( 1 , 2 , 6 - 12 ) are known and isolated for the first time from this source. The structures of the isolated compounds were elucidated by advanced spectroscopic 1D and 2D NMR techniques including 1 H, 13 C, DEPT, HSQC, HMBC, COSY, NEOSY, and HR-MS and comparison with the reported literature. Furthermore, eight compounds ( 13 - 20 ) previously isolated by our group from the same source along with the currently isolated compounds ( 1 - 12 ) were screened against the CA-II enzyme. All compounds, except 6 , 8 , 14 , and 17 , were evaluated for in vitro bovine carbonic anhydrase-II (CA-II) inhibitory activity. Eventually, eleven compounds ( 1 , 4 , 5 , 7 , 9 , 10 , 12 , 13 , 15 , 18 , and 19 ) exhibited significant inhibitory activity against CA-II with IC 50 values ranging from 13.4 to 71.6 μM. Additionally, the active molecules were subjected to molecular docking studies to predict the binding behavior of those compounds. It was observed that the compounds exhibit the inhibitory potential by specifically interacting with the ZN ion present in the active site of CA-II. In addition to ZN ion, two residues (His94 and Thr199) play an important role in binding with the compounds that possess a carboxylate group in their structure.

Cardiotoxicity is a frequent undesirable phenomenon observed during oncological treatment that limits the therapeutic dose of antitumor drugs and thus may decrease the effectiveness of cancer eradication. Almost all antitumor drugs exhibit toxic properties towards cardiac muscle. One of the underlying causes of cardiotoxicity is the stimulation of oxidative stress by chemotherapy. This suggests that an appropriately designed diet or dietary supplements based on edible plants rich in antioxidants could decrease the toxicity of antitumor drugs and diminish the risk of cardiac failure. This comprehensive review compares the cardioprotective efficacy of edible plant extracts and foodborne phytochemicals whose beneficial activity was demonstrated in various models in vivo and in vitro. The studies selected for this review concentrated on a therapy frequently applied in cancer, anthracycline antibiotic-doxorubicin-as the oxidative stress- and cardiotoxicity-inducing agent.

The genus Datura (Solanaceae) contains nine species of medicinal plants that have held both curative utility and cultural significance throughout history. This genus' particular bioactivity results from the enormous diversity of alkaloids it contains, making it a valuable study organism for many disciplines. Although Datura contains mostly tropane alkaloids (such as hyoscyamine and scopolamine), indole, beta -carboline, and pyrrolidine alkaloids have also been identified. The tools available to explore specialized metabolism in plants have undergone remarkable advances over the past couple of decades and provide renewed opportunities for discoveries of new compounds and the genetic basis for their biosynthesis. This review provides a comprehensive overview of studies on the alkaloids of Datura that focuses on three questions: How do we find and identify alkaloids? Where do alkaloids come from? What factors affect their presence and abundance? We also address pitfalls and relevant questions applicable to natural products and metabolomics researchers. With both careful perspectives and new advances in instrumentation, the pace of alkaloid discovery-from not just Datura -has the potential to accelerate dramatically in the near future.

Cyclopolypeptides are among the most predominant biomolecules in nature, especially those derived from plant seeds. This category of compounds has gained extraordinary attention due to remarkable variety of structures and valuable biofunctions. These congeners display enormous variation in terms of both structure and function and are the most significant biomolecules due to their widespread bioproperties. The estrogenic activity, immunosuppressive activity, cytotoxicity, vasorelaxant activity, and other properties possessed by cyclic peptides from seeds of plants make these congeners attractive leads for the drug discovery process. The current study covers the important structural features, structure-activity relationship, synthesis methods, and bioproperties of plant seeds-originated bioactive peptides from Vaccaria segetalis, Linum usitatissimum, and Goniothalamus leiocarpus, which may prove vital for the development of novel therapeutics based on a peptide skeleton., (© 2021 Deutsche Pharmazeutische Gesellschaft.)

Plant specialized metabolites (SMs) play an important role in the interaction with the environment and are part of the plant defense response. These natural products are volatile, semi-volatile and non-volatile compounds produced from common building blocks deriving from primary metabolic pathways and rapidly evolved to allow a better adaptation of plants to environmental cues. Specialized metabolites include terpenes, flavonoids, alkaloids, glucosinolates, tannins, resins, etc. that can be used as phytochemicals, food additives, flavoring agents and pharmaceutical compounds. This review will be focused on Mediterranean crop plants as a source of SMs, with a special attention on the strategies that can be used to modulate their production, including abiotic stresses, interaction with beneficial soil microorganisms and novel genetic approaches.

The hunt for potential lead/drug molecules from different resources, especially from natural resources, for possible treatment of COVID-19 is ongoing. Several compounds have already been identified, but only a few are good enough to show potential against the virus. Among the identified druggable target proteins of SARS-CoV-2, this study focuses on non-structural RNA-dependent RNA polymerase protein (RdRp), a well-known enzyme for both viral genome replication and viral mRNA synthesis, and is therefore considered to be the primary target. In this study, the virtual screening followed by an in-depth docking study of the Compounds Library found that natural compound Cyclocurcumin and Silybin B have strong interaction with RdRp and much better than the remdesivir with free binding energy and inhibition constant value as ꞌ-6.29 kcal/mol and 58.39 µMꞌ, and ꞌ-7.93kcal/mol and 45.3 µMꞌ, respectively. The finding indicated that the selected hits (Cyclocurcumin and Silybin B) could act as non-nucleotide anti-polymerase agents, and can be further optimized as a potential inhibitor of RdRp by benchwork experiments.

Natural products are promising chemicals due to their structural diversity and bioactivities. Over the decades, a vast variety of gene clusters encoding natural products have been identified and overexpressed in microbes. Recently, the development of metabolic engineering, synthetic biology and bioinformatics strategies have facilitated target discovery and design. Microbial cells have been therefore constantly engineered for product accumulation. This review summarizes approaches of domesticating microbial hosts in producing major classes of natural products, with an emphasis on recent advances., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Plants have always been used as medicines since ancient times to treat diseases. The knowledge around the active components of herbal preparations has remained nevertheless fragmentary: the biosynthetic pathways of many secondary metabolites of pharmacological importance have been clarified only in a few species, while the chemodiversity present in many medicinal plants has remained largely unexplored. Despite the advancements of synthetic biology for production of medicinal compounds in heterologous hosts, the native plant species are often the most reliable and economic source for their production. It thus becomes fundamental to investigate the metabolic composition of medicinal plants to characterize their natural metabolic diversity and to define the biosynthetic routes in planta of important compounds to develop strategies to further increase their content. We present here a number of case studies for selected classes of secondary metabolites and we review their health benefits and the historical developments in their structural elucidation and characterization of biosynthetic genes. We cover the cases of benzoisoquinoline and monoterpenoid indole alkaloids, cannabinoids, caffeine, ginsenosides, withanolides, artemisinin, and taxol; we show how the "early" biochemical or the more recent integrative approaches-based on omics-analyses-have helped to elucidate their metabolic pathways and cellular compartmentation. We also summarize how the knowledge generated about their biosynthesis has been used to develop metabolic engineering strategies in heterologous and native hosts. We conclude that following the advent of novel, high-throughput and cost-effective analytical technologies, the secondary metabolism of medicinal plants can now be examined under the lens of systems biology., Competing Interests: The authors declare no conflicts of interest., (Georg Thieme Verlag KG Stuttgart · New York.)

Secondary natural products from plants are important drug leads for the development of new drug candidates for rational clinical therapy and exhibit a variety of biological activities in experimental pharmacology and serve as structural template in medicinal chemistry. The exploration of plants and discovery of natural compounds based on ethnopharmacology in combination with high sophisticated analytics is still today an important drug discovery to characterize and validate potential leads. Due to structural complexity, low abundance in biological material, and high costs in chemical synthesis, alternative ways in production like plant cell cultures, heterologous biosynthesis, and synthetic biotechnology are applied. The basis for any biotechnological process is deep knowledge in genetic regulation of pathways and protein expression with regard to todays "omics" technologies. The high number genetic techniques allowed the implementation of combinatorial biosynthesis and wide genome sequencing. Consequently, genetics allowed functional expression of biosynthetic cascades from plants and to reconstitute low-performing pathways in more productive heterologous microorganisms. Thus, de novo biosynthesis in heterologous hosts requires fundamental understanding of pathway reconstruction and multitude of genes in a foreign organism. Here, actual concepts and strategies are discussed for pathway reconstruction and genome sequencing techniques cloning tools to bridge the gap between ethnopharmaceutical drug discovery to industrial biotechnology., Competing Interests: The author declares no conflict of interest., (Georg Thieme Verlag KG Stuttgart · New York.)

Natural products are generally ingested as part of traditional herbal decoctions or in the current diet. However, in natural product research, the bioavailability of secondary metabolites is often poorly investigated. In this work, a systematic study was carried out in order to highlight the physicochemical parameters that mainly influence the passive intestinal absorption of natural products. For this, a representative set of natural products including alkaloids, coumarins, flavonoid aglycones and glycosides, and carboxylic acids was selected and their physicochemical properties were predicted using relevant Volsurf+ descriptors. The chemical space obtained with this unbiased method was then correlated with experimental passive intestinal permeability data, which highlighted the main influence of lipophilicity, global hydrophilicity, size, and the ionisation state on passive intestinal absorption of natural products. Since the pH range encountered in the intestine is wide, the influence of the ionisation was investigated deeper experimentally. The ionisation state of weakly ionisable natural products, such as flavonoid aglycones, alkaloids, and carboxylic acids, was found to prevent the passive intestinal absorption of such natural products completely. In addition, the impact of solubility issues on passive permeability results was evaluated in cases of poorly water-soluble natural products, such as flavonoid aglycones and coumarins. The biomimetic fasted state simulated fluid-version 2 was found to improve the apparent solubility of such poorly soluble natural products without influencing their permeability behaviours. The use of such a solubilising buffer was found to be well adapted to the hexadecane membrane-parallel artificial membrane permeability assay and can circumvent the solubility issues encountered with poorly soluble natural products in such an assay., (Georg Thieme Verlag KG Stuttgart · New York.)

Anxiety disorders are the most common mental illnesses affecting human beings. They range from panic to generalized anxiety disorders upsetting the well-being and psychosocial performance of patients. Several conventional anxiolytic drugs are being used which in turn results in several adverse effects. Therefore, studies to find suitable safe medicines from natural sources are being conducted by researchers. The aim of the present study is to comprehensively review phytochemical compounds with well-established anxiolytic activities and their structure-activity relationships as well as neuropsychopharmacological aspects. Results showed that phytochemicals like; alkaloids, flavonoids, phenolic acids, lignans, cinnamates, terpenes and saponins possess anxiolytic effects in a wide range of animal models of anxiety. The involved mechanisms include interaction with γ-aminobutyric acid (GABA)A receptors at benzodiazepine (BZD) and non-BZD sites with various affinity to different subunits, serotonergic 5-hydrodytryptamine (5-HT)1A and 5-HT2A/C receptors, noradrenergic and dopaminergic systems, glycine and glutamate receptors, and κ-opioid receptor as well as cannabinoid (CB)1 and CB2 receptors. Phytochemicals also modulate the hypothalamo-pituitary-adrenal (HPA) axis, the levels of pro-inflammatory cytokines like interleukin (IL)-2, IL-6, IL-1β and tumor necrosis factor (TNF)-α, and improve brain derived neurotrophic factor (BDNF) levels. Transient receptor potential cation channel subfamily V (TRPV)3, nitric oxide cyclic guanosine monophosphate (NOcGMP) pathway and monoamine oxidase enzymes are other targets of phytochemicals with anxiolytic activity. Taking together, these phytochemicals may be considered as supplements to conventional anxiolytic therapies in order to improve efficacy and reduce adverse effects. Further preclinical and clinical studies are still needed in order to recognize the structure-activity relationships, metabolism, absorption, and neuropsychopharmacological mechanisms of plantderived natural agents.

Endophytic fungi are those that live internally in apparently healthy and asymptomatic hosts. Endophytic fungi appear to be ubiquitous; indeed, no study has yet shown the existence of a plant species without endophytes. High species diversity is another characteristic of endophytic mycobiota which is depicted by the fact that it is quite common for endophyte surveys to find assemblages consisting of more than 30 fungal species per host plant species. Medicinal plants had been used to isolate and characterize directly the bioactive metabolites. However, the discovery of fungal endophytes inside these plants with capacity to produce the same compounds shifted the focus of new drug sources from plants to fungi. Bioactive natural products from endophytic fungi, isolated from different plant species, are attracting considerable attention from natural product chemists and biologists alike which is clearly depicted by the steady increase of publications devoted to this topic during the recent years. This review will highlight the chemical potential of endophytic fungi with focus on the detection of pharmaceutically valuable plant constituents as products of fungal biosynthesis. In addition, it will cover newly discovered endophytic fungi and also new bioactive metabolites reported in recent years from fungal endophytes. It summarizes the up-to-date and comprehensive information on bioactive compounds from endophytic fungi by having done a thorough survey of literature., (Copyright © 2015 Elsevier Ltd. All rights reserved.)