Essential oils (EOs) and their individual volatile organic constituents have been an inherent part of our civilization for thousands of years. They are widely used as fragrances in perfumes and cosmetics and contribute to a healthy diet, but also act as active ingredients of pharmaceutical products. Their antibacterial, antiviral, and anti-inflammatory properties have qualified EOs early on for both, the causal and symptomatic therapy of a number of diseases, but also for prevention. Obtained from natural, mostly plant materials, EOs constitute a typical example of a multicomponent mixture (more than one constituent substances, MOCS) with up to several hundreds of individual compounds, which in a sophisticated composition make up the property of a particular complete EO. The integrative use of EOs as MOCS will play a major role in human and veterinary medicine now and in the future and is already widely used in some cases,e.g., in aromatherapy for the treatment of psychosomatic complaints, for inhalation in the treatment of respiratory diseases, or topically administered to manage adverse skin diseases. The diversity of molecules with different functionalities exhibits a broad range of multiple physical and chemical properties, which are the base of their multi-target activity as opposed to single isolated compounds. Whether and how such a broad-spectrum effect is reflected in natural mixtures and which kind of pharmacological potential they provide will be considered in the context of ONE Health in more detail in this review.

Vegans are at an increased risk for certain micronutrient deficiencies, foremost of vitamin B₁₂. Little is known about the short-term effects of dietary change to plant-based nutrition on vitamin B₁₂ metabolism. Systemic biomarkers of vitamin B₁₂ status, namely, serum vitamin B₁₂ and holotranscobalamin, may respond quickly to a reduced intake of vitamin B₁₂. To test this hypothesis, 53 healthy omnivore subjects were randomized to a controlled unsupplemented vegan diet (VD, n = 26) or meat-rich diet (MD, n = 27) for 4 weeks. Vitamin B₁₂ status was examined by measurement of serum vitamin B₁₂, holotranscobalamin (holo-TC), methylmalonic acid (MMA) and total plasma homocysteine (tHcy). Holo-TC decreased significantly in the VD compared to the MD group after four weeks of intervention, whereas metabolites MMA and tHcy were unaffected. Body weight remained stable in both groups. VD intervention led to a significant reduction of cholesterol intake, and adequate profiles of nutrient and micronutrient status. Lower intake of vitamin B₁₂ was observed in VD, which was mirrored by a lower concentration of serum vitamin B₁₂ and reduced holo-TC after 4 weeks. Plasma holo-TC may be a fast-responding biomarker to monitor adequate supply of vitamin B₁₂ in plant-based individuals.

The killer cell lectin‐like receptor G1 (KLRG1) is expressed by NK and T‐cell subsets and recognizes members of the classical cadherin family. KLRG1 is widely used as a lymphocyte differentiation marker in both humans and mice but the physiological role of KLRG1 in vivo is still unclear. Here, we generated KLRG1‐deficient mice by homologous recombination and used several infection models for their characterization. The results revealed that KLRG1 deficiency did not affect development and function of NK cells examined under various conditions. KLRG1 was also dispensable for normal CD8⁺ T‐cell differentiation and function after viral infections. Thus, KLRG1 is a marker for distinct NK and T‐cell differentiation stages but it does not play a deterministic role in the generation and functional characteristics of these lymphocyte subsets. In addition, we demonstrate that E‐cadherin expressed by K562 target cells inhibited NK‐cell reactivity in transgenic mice over‐expressing KLRG1 but not in KLRG1‐deficient or WT mice. Hence, the inhibitory potential of KLRG1 in mice is rather weak and strong activation signals during viral infections may override the inhibitory signal in vivo.

Cyclotides represent a new class of natural plant compounds, which could be considered ideal “template” molecules for drug design. Their structure is characterized by a circular cystine-knot motif, comprising an amino acid chain stabilized by three conserved disulfide bonds in a knotted arrangement, and a head-to-tail cyclized peptide backbone. Our laboratories initially demonstrated their activity to modulate immune cell signaling. Following nearly a decade of extensive research, we are now aware that cyclotide-based peptides provide an outstanding opportunity to develop novel drugs for autoimmune disorders, especially multiple sclerosis. Here we review and demonstrate the potential of cyclotide-derived peptide therapeutics on their way from preclinical studies to clinical trials as promising therapeutics in immunopharmacological applications.