Licorice Root Extract

What is it?

Licorice root extract (Glycyrrhiza glabra) is a botanical ingredient containing two key bioactive compounds: glabridin and glycyrrhizin (glycyrrhizic acid). Glabridin is a potent tyrosinase inhibitor that blocks the enzyme responsible for converting tyrosine to melanin, making it one of the most effective botanical brightening agents available. Studies show glabridin inhibits tyrosinase activity by up to 50% at concentrations as low as 0.1 micrograms/mL without cytotoxicity to melanocytes — a critical advantage over hydroquinone, which can cause melanocyte death. Glycyrrhizin is the primary anti-inflammatory compound, functioning through multiple mechanisms: it inhibits phospholipase A2 (blocking prostaglandin and leukotriene synthesis), suppresses NF-kB activation, and has demonstrated cortisol-sparing activity by inhibiting 11-beta-hydroxysteroid dehydrogenase type 2. Additionally, licorice root contains liquiritin, which disperses existing melanin deposits by promoting melanin degradation in the epidermis. The combination of tyrosinase inhibition (preventing new melanin), melanin dispersal (addressing existing pigmentation), and anti-inflammatory activity (reducing post-inflammatory hyperpigmentation triggers) makes licorice root extract a comprehensive brightening ingredient suitable for sensitive skin that cannot tolerate harsher depigmenting agents.

How It Works

1. 1

   Tyrosinase Inhibition

   Glabridin binds to and inhibits tyrosinase, the rate-limiting enzyme in melanin synthesis, preventing conversion of tyrosine to DOPA and DOPA to dopaquinone.

2. 2

   Melanin Dispersal

   Liquiritin promotes the degradation and dispersal of existing melanin deposits in the epidermis, visibly reducing dark spots and patches.

3. 3

   Dual Anti-Inflammatory Suppression

   Glycyrrhizin blocks PLA2 and NF-kB inflammatory pathways while PDRN's A2A signaling independently suppresses TNF-alpha and IL-6, reducing inflammation-driven melanogenesis.

4. 4

   Cellular Repair and Renewal

   PDRN provides nucleotide substrates for DNA repair and stimulates fibroblast proliferation, accelerating the replacement of damaged, hyperpigmented cells with healthy new tissue.

Role in PDRN

Licorice root extract and PDRN create a powerful dual-pathway approach to hyperpigmentation and skin brightening that addresses the problem from both the melanin production side and the cellular repair side. Licorice root's glabridin directly inhibits tyrosinase, preventing new melanin synthesis at the enzymatic level, while liquiritin promotes the dispersal and degradation of existing melanin deposits. PDRN complements this from the repair side — by activating A2A receptors, PDRN accelerates the turnover and repair of UV-damaged cells that send aberrant melanogenesis signals, effectively reducing the upstream triggers for hyperpigmentation. The anti-inflammatory synergy is particularly powerful: glycyrrhizin's inhibition of phospholipase A2 and NF-kB blocks the prostaglandin-driven inflammatory cascade that causes post-inflammatory hyperpigmentation (PIH), while PDRN's A2A receptor signaling independently suppresses TNF-alpha and IL-6 through a separate molecular pathway. This dual anti-inflammatory action is especially valuable for melasma and PIH, where chronic low-grade inflammation perpetuates melanin overproduction. For daily use, licorice root extract products can be freely combined with PDRN serums, as both ingredients are gentle, non-photosensitizing, and work synergistically rather than competing for the same targets.

Clinical Data

Glabridin's tyrosinase inhibition has been demonstrated in multiple in vitro and clinical studies. A controlled clinical trial showed that topical application of 0.5% glabridin for 4 weeks produced a significant reduction in UVB-induced pigmentation compared to untreated control sites, with no signs of irritation. A 2003 study published in the Journal of Cosmetic Science demonstrated that licorice extract reduced melanin content in UV-irradiated guinea pig skin by 70% over 8 weeks. Glycyrrhizin's anti-inflammatory properties have been validated in dermatological studies showing significant reduction in erythema, edema, and inflammatory markers in contact dermatitis models. A split-face randomized controlled trial found that a formulation containing licorice root extract improved melasma severity scores by 30% after 8 weeks of daily application. When combined with PDRN's demonstrated ability to reduce inflammatory cytokines and accelerate tissue repair through A2A signaling, the combined brightening and anti-inflammatory approach provides a mechanistically sound strategy for addressing hyperpigmentation at multiple levels — tyrosinase inhibition, melanin dispersal, inflammatory cascade suppression, and cellular repair.

Product Formats in the Wild

Common ways this ingredient is delivered in clinical and consumer products.