Herbs can be powerful

Natalia Pachura is pursuing her PhD under the supervision of Prof. Antoni Szumny (her assistant supervisor is Dr. Mariusz Dziadas from the University of Wroclaw, where she defended her master's thesis in instrumental analytics in the Department of Chemistry). 

The UPWr Doctoral School doctoral student will study popular herbs such as meadow clover, calendula, greater burdock, elderberry, yarrow and hemp. From each plant, the part that is valuable in terms of biologically active substances will be selected - flowers, leaves, rhizomes or roots. All plants will be tested, not only the dried ones, which can be simply bought online, but also the fresh plants, which will be delivered to the university in June by a company that specializes in harvesting raw herbal material.

– Drying is one of the most widely used methods of food preservation. We know from the literature how it affects the quality of the final products, and therefore the loss of volatile organic compounds. In the Department of Food Chemistry and Biocatalysis at UPWr, where I am pursuing my PhD, research has been conducted since 2010 on optimizing drying processes in the context of shaping sensory characteristics and aroma. At the same time, there are no clear statements in literature about the degree of loss of non-volatile biologically active compounds. Logic dictates that it should be small, but this simply needs to be checked – says Natalia Pachura, adding that during drying, volatile compounds evaporate, and losses usually reach from a dozen to several tens of percent of the initial content and are non-linearly dependent on the temperatures used. But phytosterols, alkaloids, lignans, saponins, di- and triterpenoids or polyphenols should not degrade because they are temperature stable.

– In our experience, it is clear that the relatively low temperature and drying time do not cause thermal degradation, evaporation or chemical transformations. At the same time, however, there are many publications every year where the authors show statistically significant losses or gains of compounds from non-volatile groups – Natalia Pachura explains, adding that according to her and her supervisors, none of these publications fully validated analytical methods in the determination of bioactive compounds, and the authors did not take into account the completely different extractivities of active compounds from fresh and dried plant material. Therefore, Natalia in her research project wants to demonstrate, by fully validating the analytical methods, the actual quantitative and qualitative changes in these compounds.

Non-volatile bioactive fractions will be selected for individual plants, and individual compounds shaping their functional characteristics will be isolated or purchased. At least four drying methods will be used (so-called traditional, shade and air drying, convection drying (at extreme temperatures of up to 70 °C), microwave-assisted convection drying, as well as freeze-drying. Isolated/pure bioactive compounds suspended on the developed matrices will also undergo this process, with the aim of determining their actual thermal stability. This will be a study in which the effect of the aforementioned drying methods on the behavior of selected non-volatile bioactive fractions in plant material will be determined in a fully validated manner.

– Herbs have interested me for a long time. I have studied European varieties of Ilex paraguariensis, the popular Yerba mate supporting weight loss, regulating lipid and sugar metabolism, but also due to its high caffeine content considered a substitute for coffee. In my master's thesis, on the other hand, I studied the synthesis of a glycosidic derivative of the antibiotic chloramphenicol, which is water-soluble – says Natalia, who first became involved with the Wrocław University of Environmental and Life Sciences as a technician in the Department of Food Chemistry and Biocatalysis – it was her master's thesis and the skills she gained while working on it that made Prof. Szumny decide to take her on board. And after six months of work, she decided to recruit for the UPWr Doctoral School.

– I had been thinking about a doctorate for a long time, but thanks to the technician's work I was able to get acquainted with all the equipment, apparatus, and research techniques. And it was a really good start, because I have been at the Doctoral School for three years now – says Natalia Pachura with a smile.

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