J. Cosmet. Sci., 57, 205-214 (May/June 2006) Chitosan beads loaded with essential oils in cosmetic formulations C. ANCHISI, M. C. MELON!, and A. M. MACCIONI, Dipartimento Farmaco Chimico Tecnologico, Facolta di Farmacia, Universita degli Studi di Cagliari, Via Ospedale 72, 1-09124 Cagliari, Italy. Accepted for publication December 2, 2005. Presented in part at the XXVI Congreso Internacional de la Sociedad Farmacetttica def Mediterrdneo Latino, Medicamentos del siglo XXI: lnnovadores y Genericos, Palma de Mallorca, September 16-18, 2004. Synopsis The aim of this work is to evaluate the stability and release of chitosan beads loaded with volatile molecules of Mentha piperita essential oil (E.O.) in a cosmetic formulation. The ability of the beads to quickly release Mentha piperita E.O. during use of a cosmetic formulation such as a bath foam is also assessed. The chitosan beads were produced with three different chitosan dispersions gelled with two different gelling solutions: (a) a 10% solution of sodium hydroxide (NaOH) and (b) a 4% solution of sodium tripolyphosphate (TPP). A few properties of six bead samples loaded with Mentha piperita E.O. are assessed. The properties are morphology, size, swelling ability, encapsulation efficiency, stability in time, and fast release of Mentha piperita E.O. during the use phase of the cosmetic formulation. INTRODUCTION Essential oils are the highly concentrated, volatile, aromatic products of natural plants that accumulate in specialized structures such as oil cells, glandular trichomes, and oil or resin ducts. In some cases they seem to be a part of the plant's immune system. In others they may simply be the end products of metabolism (1). Essential oils, therefore, contain the true essence (or "soul" or life force) of the plant from which they derive, and are found in a few of the plant's elements, such as the flowers, leaves, stems, roots, or other parts, depending on the plant (2). Chemically speaking, essential oils contain hundreds of organic constituents, including hormones, vitamins, and other natural elements that work at many different levels. In aromatic plants, the essential oils are mostly volatile compounds that give them their distinctive aroma (3 ). Address all correspondence to A. M. Maccioni. 205

206 JOURNAL OF COSMETIC SCIENCE The chemical composition and aroma of essential oils can provide valuable psychological and physical-therapeutic benefits. These are usually obtained by methods that include inhalation or the application of the diluted essential oil to the skin. As they are often very concentrated, essential oils should never be used undiluted on the skin, and they are often diluted with carrier oils (such as sweet almond oil, apricot kernel oil, olive oil, etc). On applying these blends by rubbing, the tiny molecules of the essential oils are absorbed through the skin. They then dissolve in the body's natural fats and fluids that flow through the lymphatic and blood system, causing it to relax, stimulate, detoxify, and regenerate (4). Careful inhalation of essential oils can also provide therapeutic benefits the aromas are perceived by the olfactory system, which passes on signals to the limbic system in the brain. The brain then responds to a particular scent by affecting our emotions and our chemical balance. Moreover, essential oil molecules enter the lungs and are absorbed into the bloodstream (5 ). It is for these reasons that essential oils are used in aromatherapy, cosmeticology, pharmaceutics, and in many other applications. In these work we have chosen Mentha piperita essential oil (Mentha piperita E.O.), which is considered one of the oldest and most highly considered herbs for its remarkable properties. Mentha piperita E.O. has a considerable number of therapeutic properties: it is an analgesic, an antiseptic, an anti-spasmodic, an expectorant, a stimulant, and a vasoconstrictor, besides possessing other properties (6,7). It can be very useful against dermatitis, acne, and scabies, and can relieve itching, sunburn, and inflammations of the skin. In addition to these properties, Mentha piperita E.O. is also widely used in cos­ meticology for its cooling effect and because it helps to ease tension and stress. For these reasons, Mentha piperita E.O. is frequently used in cosmetic cleansing formulations such as soaps, foam baths, dentifrices, mouthwashes, and foot creams. The volatile constituents of all essential oils and therefore also of Mentha piperita E.O. are a complex mixture of organic compounds, some of which are less stable, and may therefore undergo chemical alteration in the presence of light or under high tempera­ tures. The aim of this study was to evaluate the ability of particle polymeric systems, such as chitosan beads, to load, protect, and keep for an adequate storage time the volatile molecules of Mentha piperita E.O. Additionally, when beads are formulated into a cosmetic formulation (such as a bath foam), the rate of release during conditions of use was determined. MATERIALS AND METHODS MATERIALS High-molecular-weight [2.000.000 (hC)} 75% deacetylation chitosan and medium­ molecular-weight [750.000 (mC)} 75-85% deacetylation chitosan, sodium tripolyphos­ phate (TPP), and sodium hydroxide (NaOH) were purchased from Aldrich (Milan, Italy). Glycolic acid, Mentha piperita E.O., and base bath foam (BBF composition: water, sodium lauryl sulfate, cocamidopropyl betaine, cocamide DEA, sodium chloride, and bromo-2-nitropane-1,3-diol) were supplied by Galeno (Prato, Italy). Distilled water was further purified with a Milli-Q® System (Millipore, Bedford, MA). All solvents used were analytical grade.