Inspired by Nature: Redox Modulators and Natural Nanoparticles ^†

Abstract

Numerous secondary metabolites found in edible plants modulate intracellular redox processes and are suggested to prevent certain diseases, especially in ageing organisms. Since such nutraceuticals provide the basis for new and innovative designer diets and therapies, extracting these substances and their potential from plants has become a focus of research, with nanotechnology and natural nanoparticles at the centre of some of these developments.

In recent decades, it has become apparent that Oxidative Stress (OS) plays a major role in the formation and progression of many human diseases, in particular those related to ageing and the elderly population. Traditionally, medications have been administered to prevent or slow down these ailments. In societies affected by demographic changes, such (poly-)medication is not always feasible and, in any case, places a massive burden on the individual, the society, the environment and the economy.

Nutrition provides a promising alternative. Plants and mushrooms tend to be rich in phytochemicals and many secondary metabolites, including Reactive Sulfur Species (RSS) and Reactive Selenium Species (RSeS), are able to modulate intracellular redox processes [1,2,3]. Compounds such as allicin and polysulfides found in many Allium plants, for instance, can interact with the “cellular thiolstat” [4]. Such agents are moderately reactive, affect numerous cellular processes, exhibit pronounced antioxidant and also cyto-toxic activities and, therefore, have been linked to certain preventive or even therapeutic actions [5,6,7,8,9,10]. Together, a balanced cocktail of such biologically active nutritional components may provide a promising and also more applicable alternative to extensive medication. Additionally, the global market place—for food—also implies that it is now possible to design diets which may address specific needs, for instance for specific sub-populations and age groups.

Despite these advantages, there are still some challenges associated with this strategy. One major obstacle, for example, is the low solubility and hence bioavailability of many secondary metabolites, such as polyphenols. Rather than simply consuming the relevant food, complicated extraction and formulation methods are required to produce adequate food supplements. Here, nanotechnology provides potential solutions. It is now possible to produce nanoparticles of the relevant plant materials with comparable ease, for instance by milling or fermentation. These nanosized materials are entirely “natural” as far as their chemical composition is concerned, and often exhibit an amazing release profile for active ingredients and therefore also considerable biological activity [11,12,13,14]. Nanosized plant materials rich in biologically active ingredients may therefore unlock the considerable potential of many food items, and possibly also of materials which so far have been considered as “waste”, such as the spent coffee ground, grape seeds and various shells, leftovers and peels [15]. At the same time, nanoscopic particles of sulfur and selenium generated by and in microorganisms may represent interesting preparations for agricultural applications [16,17,18].

In both cases, the combination of phytochemistry and nanotechnology promises access to new biological activities and innovative applications in various areas, from nutrition and medicine to agriculture and cosmetics.