4-hydroxycoumarin (4HC) synthesis. Advantages, applications and possible future developments of a new methodology

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Blood cells - 3D RenderingThe University of Georgia (UGA) developed a new method for the synthesis of 4-hydroxycoumarin (4HC) that promises to be cheaper and more environmentally friendly than those currently in use

Simone Montonati

The 4HC is a molecule with anticoagulant properties (by antagonism of vitamin K) used as the starting compound for the production of specific drugs (e.g.: Warfarin and Acenocoumarol) known for their role in the treatment of thromboembolic diseases. The production of this molecule is currently carried out by means of chemical synthesis and through the use of petroleum products, which leads to the double drawback of using a non-renewable resource and creating potentially harmful byproducts.

The new method developed by the team of UGA College of Engineering and published on Nature Communications promises to completely eliminate the use of petroleum in the various process steps, limiting consequently the production costs and avoiding potentially harmful byproducts. The technique involves the use of the bacterium E. coli in order to convert simple sugars into complex molecules required for the production of anticoagulants. Surprisingly it has been sufficient to incorporate a single enzyme to eliminate the bottleneck which was limiting the effectiveness of the biosynthetic mechanism. The optimization obtained by metabolic engineering techniques has pointed out the potential for scale-up of this new biosynthetic mechanism, making possible an efficient synthesis of 4HC and the semi-synthesis in situ of Warfarin. The developed method, however, can also be applied to the production of other pharmaceutical substances for which the 4HC is a parent compound, for example Acenocoumarol, Dicumarol, and Phenprocoumon.

The researchers emphasize the importance of the category of drugs involved in the research that, despite having been approved for medical use 60 years ago, remains one of the most popular and effective way to treat vascular occlusions (those diseases in United States and Europe cause, according to estimates, about 800,000 victims a year). Warfarin, for example, is one of the most widely prescribed oral anticoagulants in the world, with a global market worth about $ 300 million in 2008. Moreover, in Europe are also popular Acenocoumarol and Phenprocoumon who share the same basic structure and of which the 4HC is a close precursor. The ambition of researchers, however, is to extend the application of microbial biosynthesis also to the preparation of other pharmaceutical products. Similar processes have in fact already been applied, by the same team, to the salicylic acid synthesis, used in the production of aspirin and of products for skin care.

The technique for the production of microbial biosynthesis 4HC, at the moment, has been tested only on a laboratory level but researchers believe that it can be easily applied also to the industrial level. We asked Yuheng Lin, one of the authors of the research that led to the new technique, to illustrate the advantages, applications and possible future developments of this methodology.

This technique does not use petroleum-based products and it produces no harmful byproducts: are the performances in terms of time and quality of production at the same level compared to the chemical synthesis?

After down-stream isolation and purification processes, the quality of the final product should be the same with or even higher than that made from petroleum-based chemicals. 4HC we create in the lab is perfectly suited to be used in preparation of anticoagulants products like Warfarin. But it is hard to compare the “time” between a microbial process and chemical processes because they have different mechanisms. The greatest advantages of microbial production are certainly the sustainability, environmental compatibility and low production cost. The engineered microbes “eat” very cheap and renewable feedstock (like sugars and glycerol) and produce high value compounds.

What is the value of the energy and cost savings achieved thank to the microbial synthesis?

Currently this work is still on the lab scale. So at this time it is difficult to accurately calculate the energy and cost savings. In any case our aim is to reduce the cost by at least 50% than the current commercial production approach.

In your opinion which other products of the chemical and pharmaceutical industry could be efficiently produced by this technique?

So far a variety of molecules have been commercially produced by microbial approaches, including bio-fuels (e.g. ethanol and biodiesel), bulk chemicals (e.g. succinic acid, pyruvate and lactic acid), nutraceuticals (e.g. amino acids) and pharmaceuticals (e.g. antibiotics). In addition, the scale-up productions of many other valuable compounds are under development. The development of metabolic engineering and synthetic biology will allow microbes to produce more complicated pharmaceuticals (e.g. Warfarin, Artimisinin, Taxol).

Could this methodology, if extended to the industrial production level, be applied also to small and medium plants or the required needs could limit the SME involvement?

This technique can actually be applied in SMEs but it requires a workplace and certain equipment, like bio-reactors and separation systems. Concerning the investment, it really depends on the production scale.

The experiments were conducted on a small scale: which improvements are required to make the technique productively applicable to industrial level?

At current stage, we have seen its potential for commercialization on the lab scale: For actual commercialized production, further scale-up experimentation is needed to optimize the production condition and minimize the cost.

Which other projects regarding the environmental sustainability of production processes in the chemical and pharmaceutical industries is the UGA carrying out?

UGA has some other such projects. Many professors in the College of Engineering are focusing on the sustainable production of bulk chemicals and pharmaceuticals: the faculty is also active in various fields related to biotechnology applications: Biochemical, Bioconversion Engineering, Bioenergy, Biomedical, etc.

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