Does the immune system of plant and animal kingdoms share any pathways or mechanisms of action in phytotherapy

Abstract

The question arises from the need to understand why the use of phytotherapy may modulate the immune responses even in the animal kingdom as reported by some authors.1 In fact, even if the traditional use of herbal medicine products may guarantee efficacy, for very few medical plants scientific data on mechanisms of action are available.2 The term Phytotherapy, derived from the Greek words ‘Phyto’ and ‘therapy’, was introduced into science by the French physician Henri Leclerc (1870-1955) and indicates the therapy practiced with medicaments of vegetable origin. A study conducted by the World Health Organization had reported that about 80% of world’s population relies on traditional medicine. The history of phytotherapy is very old and was presumably one of the first therapeutic methods undertaken by man. Already in ancient times (since the Egyptian and Mesopotamian era), mankind was so fascinated by the therapeutic action of plants that for centuries magical and divine properties were attributed to them. Later on, humans have learnt by experience and observations how to use plants correctly and since the nineteenth century the empirical use of plants has been brought back within the boundaries of rationality and scientific rigor. But in what way has man been using these plants for millenia? These ‘preparations’ of vegetable origin have always been used through essentially three administration routes: at a lesser extent, by local applications or fumigation, otherwise mainly by ingestion. The administration of herbal medicine products through the oral route may represent a crucial point, as we will discuss below, to explain the efficacy of the traditional medicine. Therefore, the text found in the work On Aliment: “In food excellent medication, in food bad medication, bad and good relatively”,3 nowadays attributed to the Hellenistic period, but in Antiquity (by Galenus in particular) erroneously associated with Hippocrates, brings us back to why mankind at some point has started to ingest plants or their fruits, roots and leaves in order to find in them not only nourishment and gratification, but also a therapeutic remedy for its illnesses. Indeed, the idea of using plants as medicine treatment was probably born from fortuitous observations or from the experiences that many plants used in nutrition could also prove to be toxic or poisonous or, better, able to improve disorders. However, also Hippocrates from Cos (around 460 BC-around 375 BC), the father of Western modern medicine, knowing that food was closely linked to health and disease, applied dietetic measures for the benefit of the sick.4 According to the World Health Organization (WHO), every vegetable that contains, in one or more of its organs, pharmacologically active substances deserves the name of a medicinal plant. The pharmacognosy studies have evidenced that the set of these pharmacologically active molecules, called phytocomplexes, have the ability to work in synergy with all components. A phytocomplex represents the integral pharmacological unit of a medical plant. Most of the natural phytocomplexes that exert therapeutic actions, once ingested, have shown to act as antioxidants (thus reducing the levels of free radicals), as anti-inflammatory molecules (thus reducing the risk of chronic inflammatory diseases), as anticancer, antimicrobial and immune modulators.1 Living organisms such as plants and animals can be considered as a laboratory of biosynthesis that must provide not only for their own needs but also for their own defense. The afore mentioned phytocomplexes may, therefore, represent the set of molecules developed even to protect the plant life itself. Indeed, plants as well as animal beings are constantly attacked by environmental pathogens that through their entry into these living organisms look for their survival in turn.