Natural products have been a rich source of compounds for drug discovery. However, their use has diminished in the past two decades, in part because of technical barriers to screening natural products in high-throughput assays against molecular targets. Here, we review strategies for natural product screening that harness the recent technical advances that have reduced these barriers. We also assess the use of genomic and metabolomic approaches to augment traditional methods of studying natural products, and highlight recent examples of natural products in antimicrobial drug discovery and as inhibitors of protein-protein interactions. The growing appreciation of functional assays and phenotypic screens may further contribute to a revival of interest in natural products for drug discovery.

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The re-emergence of natural products for drug discovery in the genomics era

https://cyberleninka.org/article/n/132565.pdf

Discovery and resupply of pharmacologically active plant-derived natural products: A review.

Saccharomyces cerevisiae is engineered to produce high concentrations of artemisinic acid, a precursor of the artemisinin used in combination therapies for malaria treatment; an efficient and practical chemical process to convert artemisinic acid to artemisinin is also developed. Artemisinin-based combination therapies are the treatment of choice for uncomplicated Plasmodium falciparum malaria, but the supply of plant-derived artemisinin can sometimes be unreliable, causing shortages and high prices. This manuscript describes a viable industrial process for the production of semisynthetic artemisinin, with the potential to help stabilize artemisinin supply. The process uses Saccharomyces cerevisiae yeast engineered to produce high yields of artemisinic acid, a precursor of artemisinin. The authors have also developed an efficient and scalable chemical process to convert artemisinic acid to artemisinin. In 2010 there were more than 200 million cases of malaria, and at least 655,000 deaths1. The World Health Organization has recommended artemisinin-based combination therapies (ACTs) for the treatment of uncomplicated malaria caused by the parasite Plasmodium falciparum. Artemisinin is a sesquiterpene endoperoxide with potent antimalarial properties, produced by the plant Artemisia annua. However, the supply of plant-derived artemisinin is unstable, resulting in shortages and price fluctuations, complicating production planning by ACT manufacturers2. A stable source of affordable artemisinin is required. Here we use synthetic biology to develop strains of Saccharomyces cerevisiae (baker’s yeast) for high-yielding biological production of artemisinic acid, a precursor of artemisinin. Previous attempts to produce commercially relevant concentrations of artemisinic acid were unsuccessful, allowing production of only 1.6 grams per litre of artemisinic acid3. Here we demonstrate the complete biosynthetic pathway, including the discovery of a plant dehydrogenase and a second cytochrome that provide an efficient biosynthetic route to artemisinic acid, with fermentation titres of 25 grams per litre of artemisinic acid. Furthermore, we have developed a practical, efficient and scalable chemical process for the conversion of artemisinic acid to artemisinin using a chemical source of singlet oxygen, thus avoiding the need for specialized photochemical equipment. The strains and processes described here form the basis of a viable industrial process for the production of semi-synthetic artemisinin to stabilize the supply of artemisinin for derivatization into active pharmaceutical ingredients (for example, artesunate) for incorporation into ACTs. Because all intellectual property rights have been provided free of charge, this technology has the potential to increase provision of first-line antimalarial treatments to the developing world at a reduced average annual price.

/pdf/high-level-semi-synthetic-production-of-the-potent-55hs1z75wy.pdf

High-level semi-synthetic production of the potent antimalarial artemisinin

Advanced biofuels produced by microorganisms have similar properties to petroleum-based fuels, and can 'drop in' to the existing transportation infrastructure. However, producing these biofuels in yields high enough to be useful requires the engineering of the microorganism's metabolism. Such engineering is not based on just one specific feedstock or host organism. Data-driven and synthetic-biology approaches can be used to optimize both the host and pathways to maximize fuel production. Despite some success, challenges still need to be met to move advanced biofuels towards commercialization, and to compete with more conventional fuels.

Microbial engineering for the production of advanced biofuels

https://backend.orbit.dtu.dk/ws/files/123537793/Engineering_Cellular_Metabolism.pdf

Engineering Cellular Metabolism

Malaria, caused by Plasmodium sp, results in almost one million deaths and over 200 million new infections annually. The World Health Organization has recommended that artemisinin-based combination therapies be used for treatment of malaria. Artemisinin is a sesquiterpene lactone isolated from the plant Artemisia annua. However, the supply and price of artemisinin fluctuate greatly, and an alternative production method would be valuable to increase availability. We describe progress toward the goal of developing a supply of semisynthetic artemisinin based on production of the artemisinin precursor amorpha-4,11-diene by fermentation from engineered Saccharomyces cerevisiae, and its chemical conversion to dihydroartemisinic acid, which can be subsequently converted to artemisinin. Previous efforts to produce artemisinin precursors used S. cerevisiae S288C overexpressing selected genes of the mevalonate pathway [Ro et al. (2006) Nature 440:940–943]. We have now overexpressed every enzyme of the mevalonate pathway to ERG20 in S. cerevisiae CEN.PK2, and compared production to CEN.PK2 engineered identically to the previously engineered S288C strain. Overexpressing every enzyme of the mevalonate pathway doubled artemisinic acid production, however, amorpha-4,11-diene production was 10-fold higher than artemisinic acid. We therefore focused on amorpha-4,11-diene production. Development of fermentation processes for the reengineered CEN.PK2 amorpha-4,11-diene strain led to production of > 40 g/L product. A chemical process was developed to convert amorpha-4,11-diene to dihydroartemisinic acid, which could subsequently be converted to artemisinin. The strains and procedures described represent a complete process for production of semisynthetic artemisinin.

https://www.pnas.org/content/pnas/109/3/E111.full.pdf

Production of amorphadiene in yeast, and its conversion to dihydroartemisinic acid, precursor to the antimalarial agent artemisinin

Artemisinin is a sesquiterpene lactone endoperoxide with potent antimalarial properties, recommended by the World Health Organization for the treatment of malaria in artemisinin combination therapies (ACTs). It is extracted from the plant Artemisia annua, but its supplies are limited and its price is volatile. In order to increase supply and stabilize the price of artemisinin, a semisynthesis has been developed, whereby an artemisinin precursor (amorpha-4,11-diene) is produced in microbes and the isolated precursor converted chemically to artemisinin. Escherichia coli has been engineered to produce amorpha-4,11-diene by the expression of a heterologous mevalonate pathway along with amorpha-4,11-diene synthase (ADS) from A. annua. Development of the E. coli platform to increase production of amorpha-4,11-diene from 24 mg/L to >25 g/L is described. ADS has also been expressed in the yeast model system Saccharomyces cerevisiae which, following manipulation of the mevalonate pathway, produced 150 mg/L of amorpha-4,11-diene. The cDNAs encoding the cytochrome P450 that oxidizes amorpha-4,11-diene to artemisinic acid, CYP71AV1, and its cognate reductase were isolated from A. annua and expressed in amorpha-4,11-diene-producing E. coli and yeast, leading to the production of >1 g/L artemisinic acid from both organisms. A route for the chemical conversion of artemisinic acid to artemisinin is described. Production of semisynthetic artemisinin may lead to the development of a second source of the drug for incorporation into ACTs.

Scott Fickes

Papers

High-level semi-synthetic production of the potent antimalarial artemisinin

Production of amorphadiene in yeast, and its conversion to dihydroartemisinic acid, precursor to the antimalarial agent artemisinin

Microbially Derived Semisynthetic Artemisinin