60 SKIN CARE Glabridin is known to suppress the release
of nitric oxide (NO), a free radical that can be pro-inflammatory when overproduced, and interleukin factor 1ß (IL-1ß), a potent pro-inflammatory cytokine.11
It has also
been shown to inhibit the pro-inflammatory prostaglandin E2 (PGE2) and the activity of the pro-inflammatory NF-χb and MAPK signalling pathways.12
In addition, glabridin inhibits
tyrosine, an enzyme that plays a key role in melanin production and skin pigmentation.2 Licochalcone A inhibits synthesis of NO,
,3
IL-6 and reactive oxygen species (ROS) and reduces serum levels of immunoglobulin E and G, which are involved in allergic reactions.11 It also inhibits the pro-inflammatory NF-χb pathway and activates the anti-inflammatory Keap1-Nrf2 pathway (Figure 2).4
Like
glabradin, licochalcone A inhibits tyrosine, and additionally suppresses the activity of the pro- inflammatory NLRP3 inflammasome.2,10
Clinically supported skin benefits: Hyperpigmentation, skin brightening and photo-ageing One of the skin’s key roles is to safeguard the body from the harmful effects of exposure to ultraviolet (UV) radiation. UV irradiation accelerates the production of melanin, which absorbs the UV radiation to protect skin cells and creates a tan that acts as a natural sunscreen. However, chronic UV exposure can lead to erythema (redness), photo-ageing (by damaging connective tissue in the dermis, causing wrinkles) and hyperpigmentation (including freckles and age spots, also known as solar lentigines) (Figure 3). Liquorice has traditionally been used as a skin-brightening agent. Tyrosinase is an enzyme that mediates the initial steps in melanin production, with tyrosinase inhibitors widely used in cosmetic
TLR4 TLR4/MYD88 pathway MYD88 MAPK pathway Figure 2: The main signalling pathways of anti-inflammation of liquorice flavonoids3
applications such as skin-brightening agents.13 Several liquorice extracts have been shown
to act as tyrosinase inhibitors, thereby reducing the risk of hyperpigmentation.6
This was first
demonstrated in 1998 in an in vitro study, which found that UVB-induced pigmentation and erythema in guinea pig skin were inhibited by topical application of 0.5% glabridin.7 In a clinical study comparing the effects of
topically applied glycyrrhetinic acid and CO2 fractional laser therapy on hand solar lentigines, 11 participants were split into two groups. One group received laser treatment followed by four weeks of the topical treatment with laser, and the other group underwent topical treatment only. After four weeks, all participants experienced improvements in the lentigines, with no statistical differences between the two groups.14 Licochalcone A has also been found to
demonstrate photo-protective properties. A double-blind, placebo-controlled clinical trial randomised 22 participants to application of either licochalcone A extract or a placebo on their forearms twice a day for four weeks. The test areas were then irradiated with UVA, with skin luminescence measured by ultra-weak photon emission detection. The licochalcone A group showed significantly lower levels of UVA-induced luminescence, indicating a reduction in oxidative processes.15
Eczema Atopic dermatitis is the most common type of eczema, characterised by inflammation, skin dryness and cracking, and itching severe enough to disturb sleep. Common topical treatments, including corticosteroids, antimicrobials and immunomodulators, can
cause adverse effects, particularly with long- term use. This has led to emerging interest in herbal-based products, including liquorice extracts, as efficacious alternatives with fewer side effects. The anti-inflammatory
effects of glycyrrhetinic acid PERSONAL CARE January 2025
for the safe and effective treatment of mild to moderate atopic dermatitis have been demonstrated in a multi-centre, randomised phase IV trial.16 For five weeks, 218 adults with atopic dermatitis self-administered either a 2% hydrophilic ointment with 2% glycyrrhetinic acid or a placebo cream three times a day to affected areas and areas prone to being affected. Those using the glycyrrhetinic acid cream experienced a statistically significant 80% improvement in symptoms compared to 10% using the placebo. In a clinical randomised pilot study,
participants with atopic dermatitis applied a topical cream with 0.6% glycyrrhizinic acid and 0.1% G. uralensis root extract twice daily. After two weeks, the cream significantly reduced inflammation compared to placebo and demonstrated the same efficacy for inflammation reduction as 1% hydrocortisone acetate, with no side effects.17 Licochalcone A has also shown efficacy
for atopic dermatitis. A randomised pilot study compared a moisturiser containing licochalcone A with hydrocortisone lotion for the treatment of mild to moderate atopic dermatitis in children. After six weeks of twice- daily application, the licochalcone cream was as effective as the hydrocortisone lotion.18 A 12-week, double-blind, randomised
control trial showed that an emollient containing licochalcone A prevented flares in adults with mild to moderate atopic dermatitis.9
There was a significant reduction
in the number of relapses in areas treated with the active formulation compared to placebo. Furthermore, itch severity was also significantly less pronounced during relapse in the active- treated areas compared to placebo. Contact dermatitis is a type of eczema caused
by the skin coming into contact with irritants and allergens, manifesting as an itchy rash. A recent study evaluated a gel with 8% G. glabra root as the active ingredient for the treatment of inflammatory skin conditions, and contact dermatitis in particular. The gel demonstrated anti-inflammatory, free-radical scavenging (antioxidant) and antibacterial effects, with the researchers highlighting its potential for reducing the symptoms of dermatitis.5
www.personalcaremagazine.com MAPK p38 ERK1/2 Keap1-Nrf2 pathway Licorice Flavonoids
S 349 S 349
P
P P62 P62
P62
P62 P62
P
S 349 P S 349
Keap 1 Nrf2
Nrf2 Keap 1 Jun
Pro- inflammatory cytokines
like IL-1b, IL-6 etc. NF-kB pathway IKK ERK1/2 p38 NF-kB iNOS, COX-2, TNF-a, IL-6
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76
