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WALNUT EXTRACT COMPONENT JUGLONE HAS UV ABSORPTION POTENTIAL

This article was originally published in The Tan Sheet

Executive Summary

WALNUT EXTRACT COMPONENT JUGLONE HAS UV ABSORPTION POTENTIAL, Croda VP Kevin Gallagher reported at the Society of Cosmetic Chemists' Florida Sunscreen Symposium in Orlando Sept. 31-Oct. 3. Speaking on the topic "Natural Botanical Sunscreens," Gallagher explained that juglone, a naphthoquinone found in walnut oil, reacts with keratin protein in the skin to form "sclerojuglonic" compounds that provide UV absorption. Croda is a cosmetic ingredient supplier headquartered in Parsippany, N.J. Walnut extract currently is used in European self-tanning products, in which it acts as a "staining and reacting material" in the skin, similar to the lawsone contained in henna, Gallagher said. Croda tested two types of walnut extract -- aqueous and oily - - for its monochromatic protection factors. The protection offered by the aqueous net extract was between 5 and 7, while the oily nut extract yielded a protection factor of 2 after two hours of irradiation. For the first two hours, the protection provided by the oily nut extract was lower. Although juglone levels are higher in the oily extract, Gallagher said, "it would appear that it is more difficult for the juglone to find its way out of the oily extract and into the keratin protein [in skin] to cause the reaction which will then give [skin] UV absorption properties." The testing was performed using the Diffey-Robson spectrophotometric technique, substituting lab-grown human skin cells for 3M's Transpore tape. Croda used one drop of the extract per 2 cm diameter of skin cells. The extracts were tested "as is," not in fully formulated products. Gallagher also discussed rhattanhia root, which is derived from the South American shrub krameria triandra, as a material that provides UV protection. Based on spectrophotometer testing using the oily extract of rhattanhia root, the ingredient was found to absorb 25% to 30% of the amount of UV radiation absorbed by traditional sunscreen ingredient octyl methoxycinnamate, Gallagher noted. The rhattanhia root offers a "broader" absorption range than octyl methoxycinnamate, he said, adding that rhattanhia root absorbs "slightly more" UV light than the sunscreen in the 340 nm to 380 nm range. Rhattanhia root would be suitable for use in beach products as well as cosmetics and after-sun lotions to augment an existing organic sunscreen such as octyl methoxycinnamate, Croda said. Rhattanhia root is used in sunscreens in Europe. Neither walnut extract nor rhattanhia root are listed as Category I (safe and effective) ingredients in the sunscreen tentative final monograph, which was published in May ("The Tan Sheet" May 17, p. 10-19). Croda has indicated that it is considering petitioning FDA to include the ingredients in the TFM, but has no immediate plans to do so.
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