Rhealba® Oat Plantlet Extract: Evidence of Protein-Free Content and Assessment of Regulatory Activity on Immune Inflammatory Mediators

Abstract

Owing to their high content of flavonoids and saponins, plantlets of Avena sativa L. (Poaceae) are likely to possess anti-inflammatory and immunoregulatory properties of value in the treatment of atopic dermatitis (AD). With a view to its potential use in atopic subjects at risk of developing sensitisation to dietary proteins, we prepared a plantlet extract without proteins and isolated 2 flavonoids, isoorientin-2''- O-arabinoside (1) and isovitexin-2''- O-arabinoside (2), and two saponins, avenacosides A (3) and B (4). The absence of protein in this extract was evidenced by electrophoresis and Western immunoblotting. Furthermore, Western immunoblotting demonstrated the absence of cross-reaction between grain and plantlet proteins. We evaluated the anti-inflammatory activity of the plantlet extract and its compounds IN VITRO in a model of keratinocyte inflammation: 6-keto prostaglandin F1 α production was inhibited by the plantlet extract (- 35 % and - 57 % at 10 and 30 µg/mL, respectively; p < 0.001) and isoorientin-2''- O-arabinoside (- 31 %, - 51 %, and - 56 % at 3, 10, and 30 µg/mL, respectively; p < 0.001). Intracellular interleukin-2 production in activated T lymphocytes was also inhibited by 16 %, 27 %, and 31 % with 3, 10, and 30 µg/mL plantlet extract, respectively, and by 23 % and 32 % with 3 and 10 µg/mL avenacoside A, respectively, (p < 0.001), demonstrating their immunoregulatory activity IN VITRO. The plantlet extract was also effective on the phenotype and function of dendritic cells (DC) differentiated from monocytes. It decreased the expression of major histocompatibility complex class II molecules on DC and significantly impaired their stimulatory activity on autologous T-cell proliferation (-25 %, p < 0.05). In conclusion, this protein-free oat plantlet extract exhibits anti-inflammatory and immunoregulatory activities in vitro.

Consensus‐based European guidelines for treatment of atopic eczema (atopic dermatitis) in adults and children: part I

“…In the last years, several non‐medicated products for topical treatment of AE are available on the market, which contain active ingredients, but are neither fulfilling the definition of nor needing a licence as a topical drug. These products may contain, for example, saponins, flavonoids and riboflavins from protein‐free oat plantlet extracts, or bacterial lysates from Aquaphilus dolomiae or Vitreoscilla filiformis . These lysates both improve AE lesions and influence the skin microbiome of AE patients .…”

Consensus‐based European guidelines for treatment of atopic eczema (atopic dermatitis) in adults and children: part II

“…The concerns regarding side‐effects of phytotherapy with crude plant extracts must not be generalized to emollients containing protein free oat plantlet extracts …”

The role of topical dermocosmetics in acne vulgaris

“…Another natural ingredient that has been researched for its potential efficacy in acne treatment is oat preparations which are well‐known to sooth and restore fragile skin. An oat plantlet extract has been shown to have a range of anti‐inflammatory immunomodulatory effects in keratinocytes in vitro and recently it has been shown to inhibit bacterial adhesion . Several other natural ingredients possess antioxidant, anti‐inflammatory, and/or moisturizing properties, which may be useful additions for more effective acne therapies.…”