Total Synthesis of epi-Trichosetin

Discovery and biosynthesis of macrophasetins from the plant pathogen fungus Macrophomina phaseolina

3-Decalinoyltetramic acids (DTAs) are a class of natural products with chemical diversity and potent bioactivities. In fungal species there is a general biosynthetic route to synthesize this type of compounds, which usually features a polyketide synthase-nonribosomal peptide synthetase (PKS-NRPS) and a lipocalin-like Diels-Alderase (LLDAse). Using a synthetic biology approach, combining the bioinformatics analysis prediction and heterologous expression, we mined a PKS-NRPS and LLDAse encoding gene cluster from the plant pathogenic fungus Macrophomina phaseolina and characterized the cluster to be responsible for the biosynthesis of novel DTAs, macrophasetins. In addition, we investigated the biosynthesis of these compounds and validated the accuracy of the phylogeny-guided bioinformatics analysis prediction. Our results provided a proof of concept example to this approach, which may facilitate the discovery of novel DTAs from the fungal kingdom.

Paecilosetin Derivatives as Potent Antimicrobial Agents from Isaria farinosa

Fifty-seven entomopathogenic microorganisms were screened against human pathogens and subjected to mass spectrometry molecular networking based dereplication. Isaria farinosa BSNB-1250, shown to produce potentially novel biologically active metabolites, was grown on a large scale on potato dextrose agar, and paecilosetin (1) and five new analogues (2-6) were subsequently isolated. The structures of the new compounds were elucidated using 1D and 2D NMR. The absolute configurations of compounds 1-6 were determined using Mosher ester derivatives (1, 3, 4), comparison of experimental and calculated ECD spectra (2-4 and 6), and single-crystal X-ray diffraction analysis (5). Compounds 1 and 5 exhibited strong antibacterial activity against MSSA and MRSA with MIC values of 1-2 μg/mL.

Unraveling Plant Natural Chemical Diversity for Drug Discovery Purposes

The screening and testing of extracts against a variety of pharmacological targets in order to benefit from the immense natural chemical diversity is a concern in many laboratories worldwide. And several successes have been recorded in finding new actives in natural products, some of which have become new drugs or new sources of inspiration for drugs. But in view of the vast amount of research on the subject, it is surprising that not more drug candidates were found. In our view, it is fundamental to reflect upon the approaches of such drug discovery programs and the technical processes that are used, along with their inherent difficulties and biases. Based on an extensive survey of recent publications, we discuss the origin and the variety of natural chemical diversity as well as the strategies to having the potential to embrace this diversity. It seemed to us that some of the difficulties of the area could be related with the technical approaches that are used, so the present review begins with synthetizing some of the more used discovery strategies, exemplifying some key points, in order to address some of their limitations. It appears that one of the challenges of natural product-based drug discovery programs should be an easier access to renewable sources of plant-derived products. Maximizing the use of the data together with the exploration of chemical diversity while working on reasonable supply of natural product-based entities could be a way to answer this challenge. We suggested alternative ways to access and explore part of this chemical diversity with in vitro cultures. We also reinforced how important it was organizing and making available this worldwide knowledge in an "inventory" of natural products and their sources. And finally, we focused on strategies based on synthetic biology and syntheses that allow reaching industrial scale supply. Approaches based on the opportunities lying in untapped natural plant chemical diversity are also considered.