Meristem Plant Cells as a Sustainable Source of Redox Actives for Skin Rejuvenation

Abstract

Recently, aggressive advertisement claimed a "magic role" for plant stem cells in human skin rejuvenation. This review aims to shed light on the scientific background suggesting feasibility of using plant cells as a basis of anti-age cosmetics. When meristem cell cultures obtained from medicinal plants are exposed to appropriate elicitors/stressors (ultraviolet, ultrasound ultraviolet (UV), ultrasonic waves, microbial/insect metabolites, heavy metals, organic toxins, nutrient deprivation, etc.), a protective/adaptive response initiates the biosynthesis of secondary metabolites. Highly bioavailable and biocompatible to human cells, low-molecular weight plant secondary metabolites share structural/functional similarities with human non-protein regulatory hormones, neurotransmitters, pigments, polyamines, amino-/fatty acids. Their redox-regulated biosynthesis triggers in turn plant cell antioxidant and detoxification molecular mechanisms resembling human cell pathways. Easily isolated in relatively large quantities from contaminant-free cell cultures, plant metabolites target skin ageing mechanisms, above all redox imbalance. Perfect modulators of cutaneous oxidative state via direct/indirect antioxidant action, free radical scavenging, UV protection, and transition-metal chelation, they are ideal candidates to restore photochemical/redox/immune/metabolic barriers, gradually deteriorating in the ageing skin. The industrial production of plant meristem cell metabolites is toxicologically and ecologically sustainable for fully "biological" anti-age cosmetics.

Keywords: RNS; ROS; UV; cosmetics; environmental stress; meristem plant cells; plant metabolites; polyphenols; skin photoageing; skin rejuvenation.

Figure 1

The super-family of plant secondary metabolites of actual and potential use in anti-age cosmetics. The parent molecule shikimic acid is transformed into phenylalanine. Inducible by a variety of biotic and abiotic stresses, the enzyme phenylalanine ammonia liase (PAL) is a key enzyme for polyphenol biosynthesis, having and cinnamic acid is the first product. Then, upon the action of different enzymes, such as oxidases, peroxidases, transferases, synthase, etc., numerous “off-springs” of the parent molecules are formed. DC: decarboxylase; GluT: glutamyl transferase; GlyT: glycosyl transferase; CS: coumarin synthase; SS: stilbene synthase; ChS: chalcon synthase; PPx: phenol peroxidases.

Figure 2

Metabolic and inflammatory pathways in keratinocytes affected by biotechnologically produced plant secondary metabolites. Secondary plant metabolites, mainly polyphenolics, may enhance (green asterisks) or inhibit (red asterisks) metabolic and inflammatory responses of keratinocytes to abiotic stresses (ultraviolet (UV) irradiation or reactive oxygen species (ROS) stress) or biotic signals—inflammatory cytokines, (tumor necrosis factor alpha (TNF-α) or interferon gamma (IFN-γ)), bacterial lipopolysaccharides (LPS) or ligands for epidermal growth factor receptor (EGFR).

Figure 3

Scheme of secondary metabolite production by meristem plant cells.Meristem cells are stimulated and collected from shoots, roots, flowers or leaves of grown plant under sterile conditions. Cells are cultivated and up-scaled to industrial volumes in nutrient medium and exposed to biotic or abiotic elicitors. Medium containing secondary metabolites released from cultured plant cells is collected, secondary metabolites are isolated and analysed both qualitatively and quantitatively. Biological activity of secondary metabolites is determined in silico, in vitro in acellular and cell-containing systems, organ cultures, and in vivo (on healthy volunteers or in clinical trials). In vivo animal studies of cosmetic ingredients are prohibited by the international law.