Synthesis and anticancer activity of focused compound libraries from the natural product lead, oroidin

Pyrrole: A Decisive Scaffold for the Development of Therapeutic Agents and Structure-Activity Relationship

An overview of pyrroles as distinct scaffolds with therapeutic potential and the significance of pyrrole derivatives for drug development are provided in this article. It lists instances of naturally occurring pyrrole-containing compounds and describes the sources of pyrroles in nature, including plants and microbes. It also explains the many conventional and modern synthetic methods used to produce pyrroles. The key topics are the biological characteristics, pharmacological behavior, and functional alterations displayed by pyrrole derivatives. It also details how pyrroles are used to treat infectious diseases. It describes infectious disorders resistant to standard treatments and discusses the function of compounds containing pyrroles in combating infectious diseases. Furthermore, the review covers the uses of pyrrole derivatives in treating non-infectious diseases and resistance mechanisms in non-infectious illnesses like cancer, diabetes, and Alzheimer's and Parkinson's diseases. The important discoveries and probable avenues for pyrrole research are finally summarized, along with their significance for medicinal chemists and drug development. A reference from the last two decades is included in this review.

Comparative Chemical Profiling and Antimicrobial/Anticancer Evaluation of Extracts from Farmed versus Wild Agelas oroides and Sarcotragus foetidus Sponges

Marine sponges are highly efficient in removing organic pollutants and their cultivation, adjacent to fish farms, is increasingly considered as a strategy for improving seawater quality. Moreover, these invertebrates produce a plethora of bioactive metabolites, which could translate into an extra profit for the aquaculture sector. Here, we investigated the chemical profile and bioactivity of two Mediterranean species (i.e., Agelas oroides and Sarcotragus foetidus) and we assessed whether cultivated sponges differed substantially from their wild counterparts. Metabolomic analysis of crude sponge extracts revealed species-specific chemical patterns, with A. oroides and S. foetidus dominated by alkaloids and lipids, respectively. More importantly, farmed and wild explants of each species demonstrated similar chemical fingerprints, with the majority of the metabolites showing modest differences on a sponge mass-normalized basis. Furthermore, farmed sponge extracts presented similar or slightly lower antibacterial activity against methicillin-resistant Staphylococcus aureus, compared to the extracts resulting from wild sponges. Anticancer assays against human colorectal carcinoma cells (HCT-116) revealed marginally active extracts from both wild and farmed S. foetidus populations. Our study highlights that, besides mitigating organic pollution in fish aquaculture, sponge farming can serve as a valuable resource of biomolecules, with promising potential in pharmaceutical and biomedical applications.

A concise review on marine bromopyrrole alkaloids as anticancer agents

Natural products have been the most important sources of chemically diverse raw materials that have inspired pharmaceutical discoveries over the past few decades. Many pharmaceutical companies are utilizing plant extracts to develop relatively crude therapeutic formulations. The interesting chemicals identified as natural products are derived from the phenomenon of biodiversity, where the interactions between the organisms and their environment formulate the diverse and complex chemical entities within them that enhance their survival and competitiveness. Marine sponges are rich sources of natural products and have provided an infinite supply of bioactive metabolites. Bromopyrrole alkaloids are a good example of marine metabolites, have a broad range of biological activity, and represent a fascinating example of chemical diversity of secondary metabolites elaborated by marine invertebrates. The isolation and synthesis of this structural class have been investigated, resulting in a series of bromopyrrole alkaloids with potential lead hits. This review presents the detailed isolation and anticancer activity of marine bromopyrrole alkaloids, and will be of interest to the wider research community both in academic and industrial settings.

A cytotoxic survey on 2‐amino‐1H‐imidazol based synthetic marine sponge alkaloid analogues

Here, we describe the synthesis and biologic activity evaluation of 20 novel synthetic marine sponge alkaloid analogues with 2-amino-1H-imidazol (2-AI) core. Cytotoxicity was tested on murine 4T1 breast cancer, A549 human lung cancer, and HL-60 human myeloid leukemia cells by the resazurin assay. A total of 18 of 20 compounds showed cytotoxic effect on the cancer cell lines with different potential. Viability of healthy human fibroblasts and peripheral blood mononuclear cells upon treatment was less hampered compared to cancer cell lines supporting tumor cell specific cytotoxicity of our compounds. The most cytotoxic compounds resulted the following IC₅₀ values 28: 2.91 µM on HL-60 cells, and 29: 3.1 µM on 4T1 cells. The A549 cells were less sensitive to the treatments with IC₅₀ 15 µM for both 28 and 29. Flow cytometry demonstrated the apoptotic effect of the most active seven compounds inducing phosphatidylserine exposure and sub-G1 fragmentation of nuclear DNA. Cell cycle arrest was also observed. Four compounds caused depolarization of the mitochondrial membrane potential as an early event of apoptosis. Two lead compounds inhibited tumor growth in vivo in the 4T1 triple negative breast cancer and A549 human lung adenocarcinoma xenograft models. Novel marine sponge alkaloid analogues are demonstrated as potential anticancer agents for further development.

Seven New Alkaloids Isolated from Marine Flavobacterium Tenacibaculum discolor sv11

Marine flavobacterium Tenacibaculum discolor sv11 has been proven to be a promising producer of bioactive nitrogen-containing heterocycles. A chemical investigation of T. discolor sv11 revealed seven new heterocycles, including the six new imidazolium-containing alkaloids discolins C-H (1−6) and one pyridinium-containing alkaloid dispyridine A (7). The molecular structure of each compound was elucidated by analysis of NMR and HR-ESI-MS data. Furthermore, enzymatic decarboxylation of tryptophan and tyrosine to tryptamine and tyramine catalyzed by the decarboxylase DisA was investigated using in vivo and in vitro experiments. The antimicrobial activity of the isolated compounds (1−7) was evaluated. Discolin C and E (1 and 3) exhibited moderate activity against Gram-positive Bacillus subtilis DSM10, Mycobacterium smegmatis ATCC607, Listeria monocytogenes DSM20600 and Staphylococcus aureus ATCC25923, with MIC values ranging from 4 μg/mL to 32 μg/mL.

Bacillimidazoles A-F, Imidazolium-Containing Compounds Isolated from a Marine Bacillus

Chemical investigations of a marine sponge-associated Bacillus revealed six new imidazolium-containing compounds, bacillimidazoles A-F (1-6). Previous reports of related imidazolium-containing natural products are rare. Initially unveiled by timsTOF (trapped ion mobility spectrometry) MS data, extensive HRMS and 1D and 2D NMR analyses enabled the structural elucidation of 1-6. In addition, a plausible biosynthetic pathway to bacillimidazoles is proposed based on isotopic labeling experiments and invokes the highly reactive glycolytic adduct 2,3-butanedione. Combined, the results of structure elucidation efforts, isotopic labeling studies and bioinformatics suggest that 1-6 result from a fascinating intersection of primary and secondary metabolic pathways in Bacillus sp. WMMC1349. Antimicrobial assays revealed that, of 1-6, only compound six displayed discernible antibacterial activity, despite the close structural similarities shared by all six natural products.

Pharmacological Activities of Extracts and Compounds Isolated from Mediterranean Sponge Sources

Marine pharmacology is an exciting and growing discipline that blends blue biotechnology and natural compound pharmacology together. Several sea-derived compounds that are approved on the pharmaceutical market were discovered in sponges, marine organisms that are particularly rich in bioactive metabolites. This paper was specifically aimed at reviewing the pharmacological activities of extracts or purified compounds from marine sponges that were collected in the Mediterranean Sea, one of the most biodiverse marine habitats, filling the gap in the literature about the research of natural products from this geographical area. Findings regarding different Mediterranean sponge species were individuated, reporting consistent evidence of efficacy mainly against cancer, infections, inflammatory, and neurological disorders. The sustainable exploitation of Mediterranean sponges as pharmaceutical sources is strongly encouraged to discover new compounds.

Synthesis and in vitro cytotoxicity evaluation of isatin-pyrrole derivatives against HepG2 cell line

This paper reports the synthesis and in vitro cytotoxicity evaluation of isatin-pyrrole derivatives 5–8, obtained from the appropriate isatins with pyrrole, with good yields and purity. The product structures were confirmed through spectroscopy methods. Furthermore, the MTT assay on the human liver cancer HepG2 cell lines revealed moderate activity in all compounds, which was highest in sample 6 (IC50 0.47 µM). The anticancer activity was affiliated with the presence of a nitro group at C-5 and N-methyl of the isatin scaffold.

Cytotoxic Alkaloids Derived from Marine Sponges: A Comprehensive Review

Marine sponges (porifera) have proved to be a prolific source of unique bioactive secondary metabolites, among which the alkaloids occupy a special place in terms of unprecedented structures and outstanding biological activities. Identification of active cytotoxic alkaloids extracted from marine animals, particularly sponges, is an important strive, due to lack of knowledge on traditional experiential and ethnopharmacology investigations. In this report, a comprehensive survey of demospongian bioactive alkaloids in the range 1987-2020 had been performed with a special emphasis on the potent cytotoxic activity. Different resources and databases had been investigated, including Scifinder (database for the chemical literature) CAS (Chemical Abstract Service) search, web of science, Marin Lit (marine natural products research) database. More than 230 representatives of different classes of alkaloids had been reviewed and classified, different genera belonging to the phylum porifera had been shown to be a prolific source of alkaloidal molecules, including Agelas sp., Suberea sp., Mycale sp., Haliclona sp., Epipolasis sp., Monanchora sp., Crambe sp., Reniera sp., and Xestospongia sp., among others. The sufficient production of alkaloids derived from sponges is a prosperous approach that requires more attention in future studies to consider the constraints regarding the supply of drugs, attained from marine organisms.

Marine Natural Products with High Anticancer Activities

This review covers recent literature from 2012-2019 concerning 170 marine natural products and their semisynthetic analogues with strong anticancer biological activities. Reports that shed light on cellular and molecular mechanisms and biological functions of these compounds, thus advancing the understanding in cancer biology are also included. Biosynthetic studies and total syntheses, which have provided access to derivatives and have contributed to the proper structure or stereochemistry elucidation or revision are mentioned. The natural compounds isolated from marine organisms are divided into nine groups, namely: alkaloids, sterols and steroids, glycosides, terpenes and terpenoids, macrolides, polypeptides, quinones, phenols and polyphenols, and miscellaneous products. An emphasis is placed on several drugs originating from marine natural products that have already been marketed or are currently in clinical trials.

Targeting acquired oncogenic burden in resilient pancreatic cancer: a novel benefit from marine polyphenols

The upsurge of marine-derived therapeutics for cancer treatment is evident, with many drugs in clinical use and in clinical trials. Seaweeds harbor large amounts of polyphenols and their anti-cancer benefit is linear to their anti-oxidant activity. Our studies identified three superlative anti-cancer seaweed polyphenol drug candidates (SW-PD). We investigated the acquisition of oncogenic burden in radiation-resilient pancreatic cancer (PC) that could drive tumor relapse, and elucidated the efficacy of SW-PD candidates as adjuvants in genetically diverse in vitro systems and a mouse model of radiation-residual disease. QPCR profiling of 88 oncogenes in therapy-resilient PC cells identified a 'shared' activation of 40 oncogenes. SW-PD pretreatment inflicted a significant mitigation of acquired (shared) oncogenic burden, in addition to drug- and cell-line-specific repression signatures. Tissue microarray with IHC of radiation-residual tumors in mice signified acquired cellular localization of key oncoproteins and other critical architects. Conversely, SW-PD treatment inhibited the acquisition of these critical drivers of tumor genesis, dissemination, and evolution. Heightened death of resilient PC cells with SW-PD treatment validated the translation aspects. The results defined the acquisition of oncogenic burden in resilient PC and demonstrated that the marine polyphenols effectively target the acquired oncogenic burden and could serve as adjuvant(s) for PC treatment.

Radiosensitization by Marine Sponge Agelas sp. Extracts in Hepatocellular Carcinoma Cells with Autophagy Induction

Although radiation therapy is an effective treatment modality in many cancers, there is an urgent need to develop therapeutic drugs capable of overcoming radioresistance or minimizing normal tissue toxicity. A wide variety of marine-derived bioactive compounds have been screened for anti-cancer drug discovery, but little is known regarding radiation therapy applications. In this study, six different extracts of marine sponges collected from the Micronesian sea were screened for anti-cancer and radiosensitizing activity. Two extracts derived from Agelas sponges collected off the coast of Kosrae and Chuuk, the Federated States of Micronesia significantly decreased clonogenic survival of hepatocellular carcinoma (HCC) cells after exposure to ionizing radiation (IR). The Agelas extracts augmented IR-induced apoptosis and accumulation of reactive oxygen species (ROS). Endoplasmic reticulum (ER) stress was increased via unfolded protein response stimulation, which induced autophagy. N-acetylcysteine, a ROS scavenger, diminished ER stress and autophagy induction effects. This result indicated that Agelas extracts may sensitize HCC cells to IR via ROS overproduction in vitro. Our findings suggest that the Agelas sp. may have potential utility in radiosensitizer development.

A focused library synthesis and cytotoxicity of quinones derived from the natural product bolinaquinone

Bolinaquinone is a natural product that is a structurally complex, cytotoxic sesquiterpene quinone. A scaffold simplification and focused library approach using a microwave-assisted Suzuki coupling gave 32 bolinaquinone analogues with good-to-excellent cytotoxicity profiles. Mono-arylbenzoquinones, Library A, were preferentially toxic towards BE2-C (neuroblastoma) cells with growth inhibition (GI₅₀) values of 4-12 µM; only the 3,4-dimethoxyphenyl 23 and 3-biphenyl 28 variants were broad-spectrum active-HT29 (colon carcinoma), U87 and SJ-G2 (glioblastoma), MCF-7 (breast carcinoma), A2780 (ovarian carcinoma), H460 (lung carcinoma), A431 (skin carcinoma), Du145 (prostate carcinoma), BE2-C (neuroblastoma), MIA (pancreatic carcinoma) and SMA (spontaneous murine astrocytoma). Library B with a second aryl moiety exhibited broad-spectrum cytotoxicity with MCF-7 cells' GI₅₀ values of 5.6 ± 0.7 and 5.1 ± 0.5 µM for 2,5-dimethoxy-3-(naphthalene-1-yl)-6-(naphthalene-3-yl) 33 and 2,5-dimethoxy-3-(biaryl-2-yl)-6-(naphthalene-3-yl) 36, respectively. Similar potencies were also noted with 2,5-dimethoxy-3,6-diphenyl 30 against A2780 (GI₅₀ = 5.9 ± 0.0 µM) and with 2,5-dimethoxy-3-(biaryl-3-yl)-6-(naphthalene-3-yl) 37 against HT29 (GI₅₀ = 5.4 ± 0.4 µM), while the 3,4-dimethoxy mono-aryl analogue 23 exhibited good levels of activity against A2780 (GI₅₀ = 3.8 ± 0.75 µM), the neuroblastoma cell line BE2-C (GI₅₀ = 3 ± 0.35 µM) and SMA (GI₅₀ = 3.9 ± 0.54 µM). Introduction of the amino-substituted Library C gave 2-(naphthalen-1-yl)-5-(naphthalen-3-yl)-3,6-bis(propylamino) 43, with excellent activity against HT29 (0.08 ± 0.0 µM), MCF-7 (0.17 ± 0.1 µM), A2780 (0.14 ± 0.1 µM), A431 (0.11 ± 0.0 µM), Du145 (0.16 ± 0.1 µM), BE2-C (0.08 ± 0.0 µM) and MIA (0.1 ± 0.0 µM).

Muscarine, imidazole, oxazole and thiazole alkaloids

Covering: July 2012 to June 2015. Previous review: Nat. Prod. Rep., 2013, 30, 869-915The structurally diverse imidazole-, oxazole-, and thiazole-containing secondary metabolites are widely distributed in terrestrial and marine environments, and exhibit extensive pharmacological activities. In this review the latest progress involving the isolation, biological activities, and chemical and biogenetic synthesis studies on these natural products has been summarized.

Pyrrole: An emerging scaffold for construction of valuable therapeutic agents

Pyrrole derivatives comprise a class of biologically active heterocyclic compounds which can serve as promising scaffolds for antimicrobial, antiviral, antimalarial, antitubercular, anti-inflammatory and enzyme inhibiting drugs. Due to their inimitable anticancer and anti-tubercular properties, researchers were inspired to develop novel pyrrole derivatives for the treatment of MDR pathogens. In the present review the main target is to focus on the development of pyrrole mimics, with emphasis based on their structure activity relationship (SAR). The present review is being obliging for the future development of pyrrole therapeutics.

Mini-review: marine natural products and their synthetic analogs as antifouling compounds: 2009-2014

This review covers 214 marine natural compounds and 23 of their synthetic analogs, which were discovered and/or synthesized from mid-2009 to August 2014. The antifouling (AF) compounds reported have medium to high bioactivity (with a threshold of EC(50) < 15.0 mg ml(-1)). Among these compounds, 82 natural compounds were identified as new structures. All the compounds are marine-derived, demonstrating that marine organisms are prolific and promising sources of natural products that may be developed as environmentally friendly antifoulants. However, this mini-review excludes more than 200 compounds that were also reported as AF compounds but with rather weak bioactivity during the same period. Also excluded are terrestrial-derived AF compounds reported during the last five years. A brief discussion on current challenges in AF compound research is also provided to reflect the authors' own views in terms of future research directions.