Unveiling the Chemical Diversity of the Deep-Sea Sponge Characella pachastrelloides

Sponges are at the forefront of marine natural product research. In the deep sea, extreme conditions have driven secondary metabolite pathway evolution such that we might expect deep-sea sponges to yield a broad range of unique natural products. Here, we investigate the chemodiversity of a deep-sea tetractinellid sponge, Characella pachastrelloides, collected from ~800 m depth in Irish waters. First, we analyzed the MS/MS data obtained from fractions of this sponge on the GNPS public online platform to guide our exploration of its chemodiversity. Novel glycolipopeptides named characellides were previously isolated from the sponge and herein cyanocobalamin, a manufactured form of vitamin B12, not previously found in nature, was isolated in a large amount. We also identified several poecillastrins from the molecular network, a class of polyketide known to exhibit cytotoxicity. Light sensitivity prevented the isolation and characterization of these polyketides, but their presence was confirmed by characteristic NMR and MS signals. Finally, we isolated the new betaine 6-methylhercynine, which contains a unique methylation at C-2 of the imidazole ring. This compound showed potent cytotoxicity towards against HeLa (cervical cancer) cells.

Advances in Biosynthesis of Natural Products from Marine Microorganisms

Natural products play an important role in drug development, among which marine natural products are an underexplored resource. This review summarizes recent developments in marine natural product research, with an emphasis on compound discovery and production methods. Traditionally, novel compounds with useful biological activities have been identified through the chromatographic separation of crude extracts. New genome sequencing and bioinformatics technologies have enabled the identification of natural product biosynthetic gene clusters in marine microbes that are difficult to culture. Subsequently, heterologous expression and combinatorial biosynthesis have been used to produce natural products and their analogs. This review examines recent examples of such new strategies and technologies for the development of marine natural products.

Modern Perspectives of Curcumin and its Derivatives as Promising Bioactive and Pharmaceutical Agents

In the current era of eco-preservation, global research has focused on using raw and sustainable natural products with new clean technologies. New pharmaceutical or pharmaceutical agents from renewable sources are considered as essential as pure chemicals or certified fragments. A variety of natural phytoconstituents have been shown to reduce the risk of certain diseases and disorders, for example, diabetes, heart disease, cancer, neoplastic, and other health disorders. And, therefore, ongoing efforts to identify specific chemicals in these foods may contribute to their positive effects on beans/grains, fruits, vegetables, etc. Many of the phytochemicals that occurred as natural products in medicinal plants offer many opportunities in natural product research due to their versatile uses and various formulation. Curcuminoids are polyphenols found in the under-soil rhizome of Curcuma longa L. and have been used for centuries for spice, culinary, and food coloring purposes, and description also documented in the alternative system of medicines such as Indian Ayurveda, Sidha, Unani, and Chinese medicine system. It has been observed from the literature that the C. longa rhizome or commonly known as turmeric has several phytochemicals to possess anti-inflammatory, hepatoprotective, neuroprotective, antioxidant, anticancer, cardioprotective properties, and many more. The review highlights the recent progress of curcumin and its derivatives as promising bioactive and pharmaceutical agents with emphasis on future research dimensions required to propose curcuminoids as promising candidates for therapeutic and pharmacology-related sectors.

Development of an agar-plug cultivation system for bioactivity assays of actinomycete strain collections

Natural products are an important source of lead compounds for the development of drug substances. Actinomycetes have been valuable especially for the discovery of antibiotics. Increasing occurrence of antibiotic resistance among bacterial pathogens has revived the interest in actinomycete natural product research. Actinobacteria produce a different set of natural products when cultivated on solid growth media compared with submersed culture. Bioactivity assays involving solid media (e.g. agar-plug assays) require manual manipulation of the strains and agar plugs. This is less convenient for the screening of larger strain collections of several hundred or thousand strains. Thus, the aim of this study was to develop a 96-well microplate-based system suitable for the screening of actinomycete strain collections in agar-plug assays. We developed a medium-throughput cultivation and agar-plug assay workflow that allows the convenient inoculation of solid agar plugs with actinomycete spore suspensions from a strain collection, and the transfer of the agar plugs to petri dishes to conduct agar-plug bioactivity assays. The development steps as well as the challenges that were overcome during the development (e.g. system sterility, handling of the agar plugs) are described. We present the results from one exemplary screening campaign targeted to identify compounds inhibiting Agr-based quorum sensing where the workflow was used successfully. We present a novel and convenient workflow to combine agar diffusion assays with microtiter-plate-based cultivation systems in which strains can grow on a solid surface. This workflow facilitates and speeds up the initial medium throughput screening of natural product-producing actinomycete strain collections against monitor strains in agar-plug assays.

InflamNat: Web-Based Database and Predictor of Anti-Inflammatory Natural Products

Natural products (NPs) are a valuable source for anti-inflammatory drug discovery. However, they are limited by the unpredictability of the structures and functions. Therefore, computational and data-driven pre-evaluation could enable more efficient NP-inspired drug development. Since NPs possess structural features that differ from synthetic compounds, models trained with synthetic compounds may not perform well with NPs. There is also an urgent demand for well-curated databases and user-friendly predictive tools. We presented a comprehensive online web platform (InflamNat, http://www.inflamnat.com/ or http://39.104.56.4/) for anti-inflammatory natural product research. InflamNat is a database containing the physicochemical properties, cellular anti-inflammatory bioactivities, and molecular targets of 1351 NPs that tested on their anti-inflammatory activities. InflamNat provides two machine learning-based predictive tools specifically designed for NPs that (a) predict the anti-inflammatory activity of NPs, and (b) predict the compound-target relationship for compounds and targets collected in the database but lacking existing relationship data. A novel multi-tokenization transformer model (MTT) was proposed as the sequential encoder for both predictive tools to obtain a high-quality representation of sequential data. Experimental results demonstrated that the proposed predictive tools achieved the desired performance in terms of AUC.

Type S Non Ribosomal Peptide Synthetases for the rapid generation of tailor-made peptide libraries

Bacterial natural products in general, and non-ribosomally synthesized peptides in particular, are structurally diverse and provide us with a broad range of pharmaceutically relevant bioactivities. Yet, traditional natural product research suffers from rediscovering the same scaffolds and has been stigmatised as inefficient, time-, labour-, and cost-intensive. Combinatorial chemistry, on the other hand, can produce new molecules in greater numbers, cheaper and in less time than traditional natural product discovery, but also fails to meet current medical needs due to the limited biologically relevant chemical space that can be addressed. Consequently, methods for the high throughput generation of new-to-nature natural products would offer a new approach to identifying novel bioactive chemical entities for the hit to lead phase of drug discovery programms. As a follow-up to our previously published proof-of-principle study on generating bipartite type S non-ribosomal peptide synthetases (NRPSs), we now envisaged the de novo generation of non-ribosomal peptides (NRPs) on an unreached scale. Using synthetic zippers, we split NRPS in up to three subunits and rapidly generated different bi- and tripartite NRPS libraries to produce 49 peptides, peptide derivatives, and de novo peptides at good titres up to 145 mgL-1. A further advantage of type S NRPSs not only is the possibility to easily expand the created libraries by re-using previously created type S NRPS, but that functions of individual domains as well as domain-domain interactions can be studied and assigned rapidly.

Natural Products: A Promising Therapeutics for Targeting Tumor Angiogenesis

Tumor-associated angiogenesis is a key target for anti-cancer therapy. The imbalance between pro-angiogenic and anti-angiogenic signals elicited by tumor cells or tumor microenvironment always results in activating “angiogenic switch”. Tumor angiogenesis functions in multi-aspects of tumor biology, including endothelial cell apoptosis, tumor metastasis, and cancer stem cell proliferation. Numerous studies have indicated the important roles of inexpensive and less toxic natural products in targeting tumor angiogenesis-associated cytokines and apoptotic signaling pathways. Our current knowledge of tumor angiogenesis is based mainly on experiments performed on cells and animals, so we summarized the well-established models for angiogenesis both in vitro and in vivo. In this review, we classified and summarized the anti-angiogenic natural agents (Polyphenols, Polysaccharides, Alkaloids, Terpenoids, Saponins) in targeting various tumor types according to their chemical structures at present, and discussed the mechanistic principles of these natural products on regulating angiogenesis-associated cytokines and apoptotic signaling pathways. This review is to help understanding the recent progress of natural product research for drug development on anti-tumor angiogenesis.

Insights into the Phytochemical and Multifunctional Biological Profile of Spices from the Genus Piper

Piper spices represent an inexhaustible reservoir of bioactive compounds that may act as drug leads in natural product research. The aim of this study was to investigate a series of methanolic fruit extracts obtained from P. nigrum (black, green, white and red), P. longum and P. retrofractum in comparative phytochemical and multi-directional biological (antimicrobial, antioxidant, anti-enzymatic and anti-melanogenic) assays. The metabolite profiling revealed the presence of 17 piperamides, with a total content of 247.75–591.42 mg piperine equivalents/g. Among the 22 tested microorganism strains, Piper spices were significantly active (MIC < 0.1 mg/mL) against the anaerobes Actinomyces israelii and Fusobacterium nucleatum. The antioxidant and anti-enzymatic activities were evidenced in DPPH (10.64–82.44 mg TE/g) and ABTS (14.20–77.60 mg TE/g) radical scavenging, CUPRAC (39.94–140.52 mg TE/g), FRAP (16.05–77.00 mg TE/g), chelating (0–34.80 mg EDTAE/g), anti-acetylcholinesterase (0–2.27 mg GALAE/g), anti-butyrylcholinesterase (0.60–3.11 mg GALAE/g), anti-amylase (0.62–1.11 mmol ACAE/g) and anti-glucosidase (0–1.22 mmol ACAE/g) assays. Several Piper extracts (10 μg/mL) inhibited both melanin synthesis (to 32.05–60.65% of αMSH+ cells) and release (38.06–45.78% of αMSH+ cells) in αMSH-stimulated B16F10 cells, partly explained by their tyrosinase inhibitory properties. Our study uncovers differences between Piper spices and sheds light on their potential use as nutraceuticals or cosmeceuticals for the management of different diseases linked to bacterial infections, Alzheimer’s dementia, type 2 diabetes mellitus or hyperpigmentation.

The use of microstructures in the authentication of powdered drug plants

Adulteration and substitution of herbal drugs are trending issues in the herbal industry, posing a serious threat to commercial natural product research. The anatomy of powdered and non-powdered samples of plant species were compared to ascertain their similarities. Air dried powdered leaf samples and unground or intact leaves, flowers and barks of eight medicinal plant species, namely, Vernonia amygdalina, Ocimum gratisimum, Trichilia monadelpha, Bridelia ferruginea, Lophira alata., Alstonia boonei, Dialium guineense and Enantia chlorantha were studied anatomically with the aim of identifying the original plant parts used in the preparation of the drugs. The microscopic studies of leaves of V. amygdalina and O. gratisimum revealed the presence of similar stomatal complex types and trichomes in both ground and unground samples. The anatomy and palynology of T. monadelpha flower revealed that bipolar, inaperturate, monopolar, monoporate, tetracolporate and triporate pollens are present in both the ground and unground samples. The microscopic study of the barks of L. alata, B. ferruginea, A. boonei, D. guineense and E. chlorantha also showed similar cells in ground and unground samples. The anatomical features are, therefore, elucidated for authentication of the originality of the medicinal plants studied.