Hydroquinone (dihydroxybenzene) at a 2% concentration is still a common skin lightening agent in the U.S., even though it is banned in Europe and some Asian countries. Other skin lighteners include kojic acid and magnesium ascorbal phosphate. Laboratoires Sérobiologiques, a division of Cognis Corporation (now owned by BASF), has introduced a new skin whitener called Radianskin PW LS 9918 (INCI: Hydroxy-phenoxy propionic acid). This white-to-beige powder is soluble in water at a concentration of 0.5-1% at a pH of 4-7. Radianskin PW LS 9918 at 4% is soluble in both butylene glycol and glyceryl cocoate-7 but insoluble in fats and oils.

As for safety factors, it is claimed to be non-cytotoxic, non-sensitizing, non-mutagenic, non-phototoxic and causes no skin irritation. Radianskin, unlike hydroquinone, only decreases the melanin pigment production and does not destroy melanocytes. It also demonstrates good photo-protective action, as it helps to protect the skin against UV-induced damage.

Cell culture tests were conducted on B16 melanocytes with the following results. Used at very low levels, Radianskin strongly decreases melanogenesis and exhibits a better depigmenting effect than ascorbyl glucoside, kojic acid, arbutin and a similar effect as hydroquinone. Apparently, it has no effect on tyrosinase. It does not directly inhibit the enzyme or its activity in melanocytes. Radianskin acts on melanogenesis through an inhibition of melanin release by melanocytes.

A cell culture medium was also used to evaluate the ability of Radianskin to protect epidermal keratinocytes in the presence of an inflammatory dose of UV light. The results showed a photo-protective and anti-inflammatory effect on human skin that helps to prevent sun damage caused by UV radiation. Another test conducted on human skin was to evaluate the ability of Radianskin to penetrate the skin. The tests indicated that Radianskin penetrated through the stratum corneum barrier and was delivered into the skin.

Below is a suggested formula whichillustrates a method of using Radianskin.

Ingredients: %WT.

Phase A

Glyceryl stearate (and) ceteareth-20 5.0

(and) ceteareth-12 (and) cetearyl

alcohol (and) cetyl palmitate

Hydrogenated vegetable glycerides 2.0

Caprylic capric triglyceride 4.0

Hexyldecanol (and) hexyldecyl 4.0

laurate

Propylheptyl caprylate 3.0

Vegetable oil 3.0

Titanium dioxide 0.5

Phase B

Water q.s. 100%

Glycerin 5.0

Propylene glycol (and) 2.5

phenoxyethanol (and) chlorphenesin

(and) methyl paraben

Sodium stearoyl glutamate 0.5

Xanthan gum 0.4

Magnesium aluminum silicate 1.0

Radianskin PW LS 9918 1.0

Sodium hydroxide 16% q.s. pH 5.0

Procedure: With constant stirring, heat phase B in main tank to 75-80°C.Heat phase A to same temperature in another container and add to main tank. Avoid incorporating air. Homogenize if necessary. Cool to room temperature.

The above formula is a soft emulsion that lightens skin and protects it from UV damage due to the presence of titanium dioxide and Radianskin. In the oil phase, the first ingredient is an O/W self-emulsifying cream base, and the other ingredients are emollients. In the water phase, the two gums, magnesium aluminum silicate and xanthan, provide viscosity, while the second item is the preservative. Sodium stearoyl glutamate is a co-emulsifier. Radianskin, of course, is the active skin lightening ingredient.

Harvey Fishman has a consulting firm located at 34 Chicasaw Drive, Oakland, NJ 07436, [email protected], specializing in cosmetic formulations and new product ideas, offering tested finished products. He has more than 30 years of experience and has been director of research at Bonat, Nestlé LeMur and Turner Hall. He welcomes descriptive literature from suppliers and bench chemists and others in the field.