A Weight-of-Evidence Approach for the Safety Evaluation of Kombucha Extract in Cosmetic Products
Ravi Persaud, Thomas Re, Viny Srinivasan
Kombucha Extract (KE) is derived from the fermentation of yeasts and bacteria with black tea, sugar, etc. It is used in a variety of cosmetic products. As Kombucha Tea, it is consumed as a beverage in many parts of the world and thought to exert a number of therapeutic benefits in metabolic diseases, arthritis, psoriasis, constipation, indigestion, hypertension, etc., although there is no strong scientific evidence to support such claims. It is considered beneficial to the skin, helping to maintain moisture and elasticity, so it appears more even in tone and texture. The KE components vary with the species of bacteria and yeasts, fermentation time, quantity of substrates in culture, and exposure conditions. Being a complex mixture, safety data is not readily available, so we utilized a weight-of-evidence (WoE) approach to support its safe use in personal care products. This evaluation entails an initial in silico screening, read-across review, in vitro skin irritation estimation, establishing allowable exposure values based on TTC, and a clinical study to confirm skin tolerance. A literature review on KE indicated ten principal constituents with small variations in composition due to the source of the extracts. The toxicity class was established by the Cramer rules using ToxTree. DEREK (for structural alerts) and OECD Toolbox (for "read-across") evaluations were performed. Octanolwater partition coefficient and water solubility (from EPISUITE) with the molecular weight were used to estimate dermal penetration. An exposure calculation for each KE constituent was done for a face cream at a use level of 3%. The exposure was then compared to allowable levels of systemic exposure for each constituent. Results from in silico analysis verified some of the KE constituents were at a safe use level. An in vitro EPISKIN assay with the 3% KE face cream demonstrated it would not be a skin irritant. A clinical study revealed that face cream was neither a skin irritant nor a sensitizer. Therefore, the WOE approach is very useful in confirming the safety of a cosmetic ingredient in a product prior to market launch.
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Date Updated: February 28, 2020