Development of a natural preservative system using the mixture of chitosan-Inula helenium L. extract

Synopsis The aim of this study was to develop a new natural preservative system making up for the weak points of chitosan as a preservative. As reported in a previous manuscript (20th IFSCC Congress, Cannes, France, 1998), the minimum inhibitory concentrations (MICs) of water-soluble chitosan against bacteria and yeast were 0.9–3.0 mg mL−1, whereas MICs of chitosan against Aspergillus niger were over 5.0 mg mL−1. However, the result of recent study showed that the MICs of Inula helenium L. extract against A. niger were below 1.0 mg mL−1. Thus, we could develop a new preservative system containing both chitosan and I. helenium L. extract named CI-mixture. MICs of CI-mixture against bacteria and fungi (yeast and mould) were 2.0–4.0 mg mL−1. When 10.0% of the mixture (the ratio of chitosan to I. helenium L. extract = 7.5% : 2.5%) was applied to cosmetic formulae such as skin lotion, milk lotion, cream and pack, it revealed appropriate preservative efficacy. Our result of the patch test also showed that this preservative system reduced skin irritation by about 30–50%, as compared to the organic preservative system. Therefore, the good natural preservative system including chitosan and Inula helenium L. extract could be incorporated in cosmetic formulations. Resume Le but de cette etude etait de developper un nouveau systeme conservateur naturel en ameliorant les proprietes du chitosan en tant que conservateur. Comme decrit dans un manuscrit precedent (20ieme Congres IFSCC Cannes, France, 1998), les C.M.I (concentrations minimales inhibitrices) du chitosan hydro-soluble contre les bacteries et levures etaient de 0.9–3 mg mL−1 et superieures a 5 mg mL−1 conte A. niger. Cependant, des resultats recents conferaient a un extrait d' Inula helenium L. des CMI contre A niger inferieures a 1 mg mL−1. Ainsi, il devenait possible de developper un systeme conservateur combinant ces deux composes (chitosan et I. helenium L.) denomme ici melange CI. Les CMI du melange CI contre les bacteries et champignons (levures et moisissures) etaient de 2–4 mg mL−1. Lorsque ce melange CI (rapport chitosan/Inula = 7.5% : 2.5%) etait introduit a 10% dans des formules cosmetiques telles que lotion cutanee, lait cutane, creme. il montrait de bonnes proprietes conservatrices. Des resultats de patch tests cutanes montraient aussi que ce systeme conservateur reduisait l'irritation cutanee d'environ 30a 50% par rapport a un systeme conservateur organique. Le systeme de conservateur naturel optimal contenant le chitosan et l'extrait d'I. helenium L. peut ainsi etre incorpore dans les formulations cosmetiques