228 JOURNAL OF COSMETIC SCIENCE fatty and amino acids and contain other essential nutrients, such as the antioxidant vitamin E, minerals, and lecithin. Essential oil is one of the many products that may be obtained from hemp: it contains many volatile compounds, mainly monoterpenes, ses­ quiterpenes, and other terpenoid-like compounds that can be isolated by steam distil­ lation. Several factors influence the yield and quality of hemp essential oil, including weather and harvesting techniques (4). The fatty-acid spectrum of hemp-seed oil is the cause of its nutritional value: compared to other unrefined edible oils, hemp-seed oil contains a very high percentage of essential fatty acids (EFA). More importantly, a high proportion (15% to 25%) is omega-3 alpha-linolenic acid, only found in significant quantities in a few other commonly used cooking oils, such as soybean and canola oils. In hemp-seed oil, the monounsaturated oleic acid contributes 10% to 15 % , and total saturated fatty acids account for 9% to 11 % of the total fatty acids. It also contains small percentages of several other polyunsaturated fatty acids (PUFAs) that play important roles in human metabolism most notable are gamma-linolenic acid (GLA, 18:3 omega- 6) and stearidonic acid (18:4 omega-3), whose content varies considerably with variety and growing conditions. The fat-soluble compounds of the vitamin E complex, tocoph­ erols and tocotrienols, are other important constituents of hemp-seed oil compared to other cold-pressed and unrefined vegetable oils-olive, sunflower, canola-it has a moderate to high content of vitamin E compounds. Typical levels are 100 to 150 milligrams per 100 grams of oil, predominantly gamma-tocopherol. This makes hemp­ seed oil a valuable source of vitamin E, one to two tablespoons meeting daily require­ ments. Finally, unrefined hemp-seed oil also contains moderate amounts of several other beneficial or even essential constituents, such as phytosterols, phospholipids, carotenes, and several minerals including calcium, magnesium, and potassium. Besides its nutritional benefits, hemp-seed oil has a number of positive effects on the skin: clinical studies have shown that PUFAs can alleviate or even resolve some skin problems, such as dry skin (5). Moreover, clinical trials with GLA supplementation have demonstrated a gradual improvement in the symptoms of a topical eczema and acne. The rediscovery of hemp-seed oil has been accompanied by advertising campaigns for body-care products containing it, by the American and European companies that have developed and promoted related products since the early 1990s. Hemp-seed oil in body-care products protects the skin by reducing dryness and may slow the skin's aging process. Hemp is an eco-friendly crop requiring no biocides and little fertilizer in comparison with cotton, for which it is an excellent substitute. Industrial hemp products can also be substituted for products derived from fossil fuels, such as synthetic fibers (textile and rope), plastics and fuel, and wood-based products including paper and particle board (6). Hemp-seed oil's high PUFA content and its high omega-3: omega-6 ratio are the main reasons for its health benefits however, the same factors cause instability and mean that the product requires careful quality control throughout the production process since unsaturated fatty acids react with free radicals and oxygen to create numerous oxidation products. This gradual oxidation of fatty acids is called rancidification: oils turn rancid faster if exposed to oxygen, heat, and especially light. However, it has also been shown by differential scanning calorimetry (DSC) that hemp-seed oil has high kinetic stability during heating and cooling (7). Microwave treatment shifts the melting range of oils to

HEMP-SEED AND OLIVE OILS 229 lower temperatures and increases oxidation temperatures, suggesting an increased pro­ tective effect upon heating (7). The physicochemical characteristics (8) of hemp-seed oil are examined through a number of analytical determinations: quality indices (free fatty-acid content, peroxide values, spectrophotometric characteristics in the UV region) parameters of oxidation processes (MDA and MONO analysis) and chlorophyll pigment content and its spectrophoto­ metric characteristics in the UV region. Hemp-seed oil was compared with a commercial virgin olive oil, since olive oil is considered to be one of the most valuable edible fats, thanks to its nutritional characteristics. The rheological characteristics of different for­ mulations of olive and hemp-seed oils were also investigated in order to determine the most suitable one for topical administration. MATERIALS Hamarnelis virginiana distillate, cetearyl alcohol, hydrolyzed milk protein, hydroxy ethyl cellulose, Polysorbate 20 (Tween 20®), Polysorbate 40 (Tween 40®), Peg-40- hydrogenated castor oil (Cremophor RH®40), and dimethicone (silicon oil 350 mPa s) were purchased from Acef. Acrylates/Cl0-30 alkyl acrylate crosspolymer (Carbopol 1382® and Pemulen TR-1 ® ) were gifts from Biochim. C 14-22 alkylalcohol/C 12-20 alkylglucoside (Montanov L®), cetearyl alcohol/cetearyl glucoside (Montanov 68EC®), polyacrylamide, C 13 _ 14 isoparaffin, laureth 7 (Sepigel 305®), and Na lauroyl oat amino acids (Proteol OAT®) were gifts from Seppic. Methyl glucose sesquistearate (20) OE (Glucamate SS E20®), and methyl glucose dioleate (Glucate DO®) were gifts from Amerchol. Imydazolidynylurea (Gram I®), methylisothiazolinone/methylchlo­ roisothiazolinone (Kathon CG®), magnesium chloride, and magnesium citrate were gifts from Sinerga S.r.l. Potassium hexadecyl hydrogen phosphate (Amphisol K®) was a gift from Roche. Poliglyceryl-3-methylglucose distearate (Tego Care 450®) was a gift from Goldschimdt Italia. Sucrose tristearate or palmitate (sucroesters DUB SE® 3S and 15 P) and sucrose mono (or di)stearate (or palmitate) (sucroesters SP® 30 and 50) were gifts from Sistema BV. C 12 _15 alkyl benzoate (Finsolv TN®) was a gift from Prodotti Gianni. Glyceryl monostearate (Cutina GMS®) was a gift from Henkel. Olive leaf extract (Eurol BT®) and Olivero 700® were gifts from B&T S.r.l. Cannabis sativa seed oil was a gift from Verdesativa, and olive oil was purchased from Carli S.r.l. LRI® solubilizer was a gift from Waker. Acetic acid, hydrochloric acid, thiobarbituric acid, trichloracetic acid, butanol, ethanol, methanol, n-hexane, diethyl ether, phenolphthalein, potassium hy­ droxide, potassium iodide, sodium chloride, sodium hydroxide, and starch were from Merck. Chlorophyll 3A (1522), Chlorophyll (5022), Chlorophyll Al 0, and Chlorophyll B 10 were from Biochim. INSTRUMENTS Viscosity of the oils was measured with a Schott-Gerate capillary viscometer (K = 0.01053, 0.4-6.0 cSt). An Abbie refractometer was used to characterize the oils, and a UV-VIS Lambda 2 spectrophotometer (Perkin-Elmer) was used to analyze the samples. Kathon CG® was quantified by high-performance liquid chromatography (HPLC) us-