Inside USBT2627: How a Ming Dynasty Herbal Decoction Became a UV-Protective Skin Extract

San-Bai decoction is a three-herb formula from Ming Dynasty Chinese medicine, traditionally swallowed to support skin health. A new study in the International Journal of Cosmetic Science asks what happens when the same blend goes onto the skin instead of into it, and the answer involves a water extract coded USBT2627 that researchers tested against UV damage through network pharmacology, a pigmented 3D skin model, and a double-blind clinical trial.

The formulation question sits at the center of the paper. Researchers led by Rui Zhang and colleagues, including Xuelan Gu, first mapped the chemistry: public pharmacology databases linked SBD's active compounds to more than 800 potential gene targets, and Gene Ontology analysis grouped those targets around oxidative stress response and immune regulation. That mapping gave the team a rationale before they touched a single skin sample.

The concentration that mattered in the clinical portion was 5% USBT2627, applied as a pretreatment before UV exposure. Against placebo, that dose raised L* values, a lightness measure, with a p-value of 0.048, and raised ITA degrees, a tan-angle measure, at p = 0.022. Erythema dropped at p = 0.016. The a* value, which tracks redness, showed a reduction too, though the effect landed just outside conventional significance at p = 0.052.

Before the clinical trial, the same extract went into a pigmented living skin equivalent, a lab-grown 3D tissue model that produces melanin. There, USBT2627 suppressed melanin accumulation, giving the researchers an in vitro basis for the skin-lightening claim they later tested on living volunteers.

Microarray transcriptomics on control, UV-exposed, and SBD-treated samples traced the mechanism to several pathways working together. The extract modulated ET-1 signalling and other pigmentation signalling pathways, the routes melanocytes use to ramp up melanin production after UV hits the skin. It also shifted oxidation response genes and cytokine signalling genes, the inflammatory messengers that drive the redness measured as erythema in the clinical arm.

The authors describe their approach as combining conventional differential expression analysis with differential network analysis, a strategy they say uncovers the mechanistic basis of the holistic benefits provided by herbal blends. Their point: San-Bai decoction's effect on skin doesn't trace to a single active ingredient hitting a single target. ET-1 signalling, oxidative response, and cytokine pathways all move together under the same 5% extract, which is the systems-level case the paper builds for treating this centuries-old oral formula as a topical ingredient worth formulating around.