COMMON milkweed is the only food source of monarch butterfly caterpillars. But for some farmers, the plant is also a valuable source of floss that can be harvested for use as hypoallergenic filler for high-end pillows, comforters and jacket linings. Floss, though, isn't the only useable portion of milkweed. Unsaturated oil in the plant's seed also has potential as a base material for sunscreen, cosmetics and skin- and hair-care products, including moisturizers and conditioners. That's the conclusion Agricultural Research Service (ARS) chemist Rogers Harry-O'kuru drew after analyzing the oil's waxes and assorted fatty acids. In studies at the ARS National Center for Agricultural Utilization Research in Peoria, Ill., Harry-O'kuru devised a procedure for using zinc chloride to catalyze the conversion of milkweed oil's triglycerides into ultraviolet (UV)-light-absorbing compounds called cinamic acid derivatives. In tests at the center's New Crops and Processing Technology Research Unit, the derivatives absorbed UV rays in the range of 260 to 360 nanometers-wavelengths that can damage skin. Additionally, the milkweed-oil derivatives accomplished this at very low concentrations of 1 to 5 percent, a range far below that approved for today's topical skin formulations, many of which use chemical fillers or sun blocks. Harry-O'kuru's milkweed-oil-based sunscreen also contains natural antioxidants such as tocopherols, which are often added to cosmetics as skin-nourishing ingredients. The sunscreen's unique combination of fats and waxes may also qualify it as biodegradable and help keep it from washing off during a swim. Its current form is a clear liquid, but gels, creams, sticks and aerosol sprays are also possible, according to Harry-O'kuru. Besides skin- and hair-care products, the UV-absorbent base material he has devised could also be tailored for use in epoxies, paints and other industrial applications. ARS has patented Harry-O'kuru's base material and is seeking an industrial partner to develop the technology further. - SD