α-Synuclein Aggregation Inhibitory Procerolides and Diphenylalkanes from the Ascidian Polycarpa procera

Cheminformatics-Guided Exploration of Synthetic Marine Natural Product-Inspired Brominated Indole-3-Glyoxylamides and Their Potentials for Drug Discovery

Marine natural products (MNPs) continue to be tested primarily in cellular toxicity assays, both mammalian and microbial, despite most being inactive at concentrations relevant to drug discovery. These MNPs become missed opportunities and represent a wasteful use of precious bioresources. The use of cheminformatics aligned with published bioactivity data can provide insights to direct the choice of bioassays for the evaluation of new MNPs. Cheminformatics analysis of MNPs found in MarinLit (n = 39,730) up to the end of 2023 highlighted indol-3-yl-glyoxylamides (IGAs, n = 24) as a group of MNPs with no reported bioactivities. However, a recent review of synthetic IGAs highlighted these scaffolds as privileged structures with several compounds under clinical evaluation. Herein, we report the synthesis of a library of 32 MNP-inspired brominated IGAs (25-56) using a simple one-pot, multistep method affording access to these diverse chemical scaffolds. Directed by a meta-analysis of the biological activities reported for marine indole alkaloids (MIAs) and synthetic IGAs, the brominated IGAs 25-56 were examined for their potential bioactivities against the Parkinson's Disease amyloid protein alpha synuclein (α-syn), antiplasmodial activities against chloroquine-resistant (3D7) and sensitive (Dd2) parasite strains of Plasmodium falciparum, and inhibition of mammalian (chymotrypsin and elastase) and viral (SARS-CoV-2 3CLpro) proteases. All of the synthetic IGAs tested exhibited binding affinity to the amyloid protein α-syn, while some showed inhibitory activities against P. falciparum, and the proteases, SARS-CoV-2 3CLpro, and chymotrypsin. The cellular safety of the IGAs was examined against cancerous and non-cancerous human cell lines, with all of the compounds tested inactive, thereby validating cheminformatics and meta-analyses results. The findings presented herein expand our knowledge of marine IGA bioactive chemical space and advocate expanding the scope of biological assays routinely used to investigate NP bioactivities, specifically those more suitable for non-toxic compounds. By integrating cheminformatics tools and functional assays into NP biological testing workflows, we can aim to enhance the potential of NPs and their scaffolds for future drug discovery and development.

A Survey of Recently Discovered Naturally Occurring Organohalogen Compounds

The discovery of naturally occurring organohalogen compounds has increased astronomically in the 55 years since they were first discovered─from fewer than 50 in 1968 to a combined 7,958 described examples in three comprehensive reviews. The present survey, which covers the period 2021-2023, brings the number of known natural organohalogens to approximately 8,400. The organization is according to species origin, and coverage includes marine and terrestrial plants, fungi, bacteria, marine sponges, corals, cyanobacteria, tunicates, and other marine organisms.

α-Synuclein Aggregation Inhibitory and Antiplasmodial Activity of Constituents from the Australian Tree Eucalyptus cloeziana

Amyloid protein aggregates are linked to the progression of neurodegenerative conditions and may play a role in life stages of Plasmodium falciparum, the parasite responsible for malaria. We hypothesize that amyloid protein aggregation inhibitors may show antiplasmodial activity and vice versa. To test this hypothesis, we screened antiplasmodial active extracts from 25 Australian eucalypt flowers using a binding affinity mass spectrometry assay to identify molecules that bind to the Parkinson's disease-implicated protein α-syn. Myrtucommulone P (1) from a flower extract of Eucalyptus cloeziana was shown to have α-syn affinity and antiplasmodial activity and to inhibit α-syn aggregation. 1 exists as a mixture of four interconverting rotamers. Assignment of the NMR resonances of all four rotamers allowed us to define the relative configuration, conformations, and ratios of rotamers in solution. Four additional new compounds, cloeziones A-C (2-4) and cloeperoxide (5), along with three known compounds were also isolated from E. cloeziana. The structures of all compounds were elucidated using HRMS and NMR analysis, and the absolute configurations for 2-4 were determined by comparison of TDDFT-calculated and experimental ECD data. Compounds 1-3 displayed antiplasmodial activities between IC50 6.6 and 16 μM. The α-syn inhibitory and antiplasmodial activity of myrtucommulone P (1) supports the hypothesized link between antiamyloidogenic and antiplasmodial activity.