Retinol alternatives for anti-ageing and hair health include plant peptides, hormones and cannabinoids finds review
Writing in Federation of American Societies for Experimental Biology (FASEB) Bio Advances, researchers from the UK’s Royal Botanic Gardens investigated current understanding around plant-based retinoid alternatives and identified areas worth researching further for the development of ingestible cosmetics. More specifically, the review spotlighted ingredient alternatives suitable for combined dermal and hair rejuvenation, identifying “potentially fruitful new areas of research”, according to the researchers.
‘Dual-acting therapy’ without negative side effects
“Finding plant-based cosmetics that cater to the desire of the community to experience both dermal and hair rejuvenating effects in one, dual-acting therapy is given impetus by the negative publicity that retinoids have received in anti-ageing therapies,” the researchers wrote.
Retinoids – long used as dermal anti-ageing ingredients in cosmetics – carried several known side effects when used in topicals, they said, including skin dryness, tightness, peeling and redness. They were also known to cause excessive hair shedding when incorporated into oral formulations, they said.
“This presents a paradox: retinoids are necessary for the continued growth and health of the hair follicle, but at higher doses lead to hair loss. Thus, oral use of retinoids to achieve younger skin may be at the cost of healthy hair and topical use can cause undesirable side effects.”
In oral blends, retinoids could “interrupt hair growth” because they promoted the expression of TGF-β from fibroblasts, which cascaded into collagen expression at the cost of keratinocyte function; responsible for influencing differentiation of dermal papilla cells that dwell at the base of the hair follicle, the researchers said.
“Fortunately, the plant kingdom provides us with a diverse array of specialised metabolites and fermentation derivatives that cater to the need to promote collagen synthesis independently of this pathway,” they said.
‘Best candidates’ in plant kingdom to replace retinoids
The review identified several promising plant-based alternatives to retinoids, categorising them into three groups: plant peptides, plant hormones and cannabinoids.
The “best candidates”, the researchers said, were lysine- or arginine-rich peptides, sourced from several species, including almond, fenugreek, pea sprouts, soy and seaweeds.
“Plant hormones” such as cytokinins and phytoestrogens were also “potentially interesting”, they said. “…Many cytokinins are agonists of the G-coupled adenosine receptors which not only modulate collagen synthesis in the dermis but are also thought to be the mechanism of minoxidil in promotion of scalp hair growth. Hence, because of the crosstalk between adenosine and cannabinoid receptors, it makes sense to try combinations of agonists/antagonists for both receptors.”
The researchers said cannabinoids were also “of interest” to try, though exclusively cannabinoid receptor 2 (CB2) agonists because there were no CB2 receptors expressed in the human hair follicle epithelium. “Dermal and hair treatments that use cannabinoids that are specific agonists for the CB2 receptor, with no binding affinity or are antagonists for CB1, are regarded as worthy of further research.”
“…The plant kingdom expresses a diverse array of metabolites that are selective agonists for CB2. Furthermore, some plant-derived metabolites have the potential to enact dual therapies for skin and hair by various mechanisms, including peptide signalling and promotion of keratinocyte proliferation/differentiation.
“The current review gives an overview of the diverse metabolites expressed by plants that can fill the same niche as the classic retinol in dermal anti-ageing therapies and improve, rather than negate, hair quality,” they concluded.
Source: FASEB Bio Advances
Published online ahead of print, doi: 10.1096/fba.2021-00022 [May 2021]
Title: “Topical and nutricosmetic products for healthy hair and dermal antiaging using ‘dual-acting’ (2 for 1) plant-based peptides, hormones, and cannabinoids”
Authors: NJ. Sadgrove and MSJ. Simmonds