Rucinol® inhibits an enzyme called tyrosinase, thereby reducing the production of the darker melanins.

•Rucinol® also inhibits another enzyme called TRP1
•The inhibition of TRP1 will shift production of black melanin towards brown or pale melanins (phaeomelanin).
•Overview of the mode of action:
•By acting in two places (on tyrosinase and TRP1), Rucinol® reduces and lightens the melanosomes. It is therefore an effective depigmenting agent.
Sophora-alpha

•Sophora-alpha acts on the outside of the melanocyte, and blocks the extracellular action of alpha-MSH, by blocking MSH receptors.
•Alpha-MSH is responsible for activating the melanin synthesis pathway.

Br J Dermatol. 2007 May;156(5):997-1004. Epub 2007 Mar 28.
Evaluation of efficacy and safety of rucinol serum in patients with melasma: a randomized controlled trial.
Khemis A, Kaiafa A, Queille-Roussel C, Duteil L, Ortonne JP.
SourceDermatology Department, Hôpital de L'Archet 2, Nice cedex 3, France.

Abstract
BACKGROUND: Melasma is a hyperpigmentation disorder predominantly affecting sun-exposed areas in women, which is often refractory to treatment. Most commercially available treatments incorporate inhibitors of tyrosinase, a key enzyme in melanin production within the melanocyte. In general, however, the efficacy of these therapies is somewhat limited. Recent studies have identified other enzymes that play an important role in melanogenesis, including tyrosinase-related protein-1 (TRP-1), which catalyses the oxidation of the melanogenetic intermediate 5,6-dihydroxyindole-2-carbolylic acid. Rucinol (4-n-butylresorcinol) has been shown to inhibit the activity of both tyrosinase and TRP-1.

OBJECTIVES: To assess the efficacy of rucinol serum 0.3% vs. the corresponding vehicle as a treatment for melasma. Secondary objectives were to evaluate local and general tolerability and to assess the skin acceptability of rucinol serum in the target population.

METHODS: In this prospective, single-centre, double-blind, randomized, vehicle-controlled, bilateral (split-face) comparative trial, 32 women with melasma were provided with two identical tubes containing rucinol serum 0.3% or vehicle. The products were each applied to one-half of the face, according to the randomization scheme, twice daily for 12 weeks (phase 1). A broad-spectrum sunscreen (sun protection factor 60) was also applied daily. Assessments at baseline, 4, 8 and 12 weeks included clinical evaluations by a dermatologist, chromametry, ultraviolet and standard photography, and assessments of skin acceptability and tolerability. After 12 weeks, patients were given the option of an additional 3-month treatment period of open full-face rucinol treatment, with reviews at 16, 20 and 24 weeks (phase 2).

RESULTS: Twenty-eight patients completed phase 1 and 26 patients completed phase 2. After 12 weeks, the clinical pigmentation score for rucinol-treated skin was significantly lower than for vehicle-treated skin (P = 0.027). During phase 2, rucinol induced a significant reduction in mean pigmentation score on the half of the face previously treated with vehicle. There was also a further, significant improvement on the rucinol-treated side of the face. Chromametry measurements showed that skin was significantly lighter and less yellow, with a strong trend towards reduced redness, following rucinol therapy compared with vehicle. Rucinol serum showed good tolerability and acceptability and was considered to have good or fair efficacy by 78% of the patient population.

CONCLUSIONS: Rucinol serum was shown to have significant efficacy compared with vehicle alone in improving melasma after 3 months of treatment, according to clinical and objective assessments of skin colour.