Nowadays, various drugs on the market are becoming more and more resistant to numerous diseases, thus declining their efficacy for treatment purposes in human beings. Antibiotic resistance is one among the top listed threat around the world which eventually urged the discovery of new potent drugs followed by an increase in the number of deaths caused by cancer due to chemotherapy resistance as well. Accordingly, marine cyanobacteria, being the oldest prokaryotic microorganisms belonging to a monophyletic group, have proven themselves as being able to generate pharmaceutically important natural products. They have long been known to produce distinct and structurally complex secondary metabolites including peptides, polyketides, alkaloids, lipids, and terpenes with potent biological properties and applications. As such, this review will focus on recently published novel compounds isolated from marine cyanobacteria along with their potential bioactivities such as antibacterial, antifungal, anticancer, anti-tuberculosis, immunosuppressive and anti-inflammatory capacities. Moreover, various structural classes, as well as their technological uses will also be discussed.

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Two novel cyclodepsipeptides containing an unusual anthranilic acid dimer and a d-phenyllactic acid residues, clavatustides A (1) and B (2), were identified from cultured mycelia and broth of Aspergillus clavatus C2WU isolated from Xenograpsus testudinatus, which lives at extreme, toxic habitat around the sulphur-rich hydrothermal vents in Taiwan Kueishantao. This is the first example of cyclopeptides containing an anthranilic acid dimer in natural products, and the first report of microbial secondary metabolites from the hydrothermal vent crab. Clavatustides A (1) and B (2) suppressed the proliferation of hepatocellular carcinoma (HCC) cell lines (HepG2, SMMC-7721 and Bel-7402) in a dose-dependent manner, and induced an accumulation of HepG2 cells in G1 phase and reduction of cells in S phase.

Chemically mediated interactions have been hypothesized to be essential for ecosystem functioning as co-occurring organisms can influence the performance of each other by metabolic means. Here, we present a co-culture device that allows co-culturing of microorganisms that are physically separated but can exchange chemical signals and metabolites. This setup was adopted to perform investigations on the secondary metabolisms of both a fungal-bacterial community and an actinomycetic-actinomycetic community. This study employed a metabolomics approach integrating LC-MS profiling, multivariate data analysis and molecular networking techniques. LC-MS measurements revealed a pronounced influence of such chemical communication on the metabolic profiles of synthetic co-culture communities with a group of molecules being induced or upregulated in co-cultures. A novel antibiotic exhibiting antibiotic properties against Klebsiella pneumoniae was unveiled in the fungal-bacterial community. Besides, a further survey of the fungal-bacterial cross-talk indicated that the production of co-culture-induced diphenyl ethers by fungi might result from the fungal response against the secretion of surfactins by bacteria in the cross-talk. This study demonstrated that the presented co-culture device and the metabolomic routine would facilitate the investigation on chemically mediated interactions in nature as well as cryptic natural products discovery.

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