Identification of an emulsifier and conditions for preparing stable nanoemulsions containing the antioxidant astaxanthinby D-M. Kim, S-S. Hyun, P. Yun, C-H. Lee, S-Y. Byun

International Journal of Cosmetic Science

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Year
2011
DOI
10.1111/j.1468-2494.2011.00682.x
Subject
Colloid and Surface Chemistry / Chemistry (miscellaneous) / Dermatology / Ageing / Drug Discovery / Pharmaceutical Science

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Text

Identification of an emulsifier and conditions for preparing stable nanoemulsions containing the antioxidant astaxanthin

D-M. Kim*, S-S. Hyun, P. Yun, C-H. Lee and S-Y. Byun *Cosmetic R&D Center, 183-5, Dodang-dong, Wonmi-gu, Bucheon-si, Gyeonggi-do, South Korea and Department of Applied Biotechnology, Ajou

University, Suwon, 443-749, Korea

Received 18 November 2010, Accepted 11 July 2011

Keywords: astaxanthin, high-pressure homogenization, nanoemulsion, particle size, zeta potential

Synopsis

In this study, oil-in-water nanoemulsions of astaxanthin were prepared by high-pressure homogenization. The influence of emulsifying conditions including emulsifier type, concentration, passing time, astaxanthin concentration and coantioxidants were optimized. The stabilities of nanoemulsions were measured using zetasizer, FF-SEM, TEM, colorimeter and particle size analyzer. The mean diameter of the dispersed particles containing astaxanthin ranged from 160 to 190 nm. The size distribution was unimodal and extended from 100 to 200 nm. The nanoemulsions prepared with glyceryl citrate/lactate/linoleate/oleate (glyceryl ester) had smaller particle size and narrower size distribution than the emulsion prepared with hydrogenated lecithin. Stable incorporation of astaxanthin in nanoemulsion was performed and checked using

HPLC, FF-SEM and TEM. The nanoemulsion was not significantly affected during storage under light and thermal condition for one month indicating that the nanoemulsion had a zeta potential of less than )41 mV, indicating a stable colloid.

Re´sume´

Dans cette e´tude des nano e´mulsions d’astaxanthine sont pre´pare´es par homoge´ne´isation a` haute pression. Les conditions d’e´mulsification sont optimise´es en terme de type et de concentration d’e´mulsionnants, de temps de passage, de concentration d’astaxanthine et de co-antioxydants. Les stabilite´s des nano e´mulsions sont e´value´es a` l’aide d’un zetasizer, de l’observation en microscopie e´lectronique simple (TEM) et sur cryofracture (FF-SEM), d’un colorime`tre et de l’analyse de la taille des particules. Le diame`tre moyen des particules disperse´es contenant l’astaxanthine allait de 160 a` 190 nm.

La distribution e´tait unimodale et s’e´tendait de 100 a` 200 nm. Les nano e´mulsions formule´es avec les glyceryl esters (glyceryl citrate/ lactate / linole´ate / ole´ate) donnaient des particules plus petites et une distribution de taille plus e´troite que celles pre´pare´es avec la le´cithine hydroge´ne´e. La stabilite´ d’incorporation de l’astaxanthine dans les nano e´mulsions a e´te´ ve´rifie´e et prouve´e par HPLC, FFSEM et TEM. Les nano e´mulsions sont reste´es stables lors du stockage d’un mois en condition de lumie`re et de tempe´rature en montrant un potentiel zeˆta infe´rieur a` )41 mV preuve d’un syste`me colloı¨dal stable.

Introduction

Excess oxygen produces some harmful oxygen species such as singlet oxygen, hydroxyl radicals, peroxyl radicals and alkoxyl radicals and so on. It usually is involved in a number of serious health disorders such as cancer, cardiovascular disease and macular degeneration [1–3]. In recent years, researchers have further shown that carotenoids possess certain properties beneficial to health, which might be helpful in the prevention of above-mentioned diseases [4].

In the cosmetic industry especially, butylated hydroxyl toluene (BHT), acerora and tocopherol are the conventionally used antioxidants for improving formulation stability and durability.

Carotenoids have also received particular attention owing to their high provitamin activity and antioxidant capacity. Astaxanthin (3, 3¢-dihydroxy-ß- ß’-carotene-4-4¢-dione) is a ketocarotenoid, used as a preferred pigment in aquaculture feeds. Owing to high antioxidant activity [5, 6], it can be used as a potential prophylactic agent against skin cancer and as a possible chemopreventive agent. Despite the availability of synthetic astaxanthin, astaxanthin from natural sources still receives more interest owing to its greater antioxidant activity and stability [7].

However, as with most carotenoids, astaxanthin is a highly unsaturated molecule, and thus, it is highly sensitive to high temperature, light and oxidative conditions which may promote the isomerization of astaxanthin into the cis form which possesses less activity than its corresponding trans configuration [8]. In addition, it is not generally used in food and cosmetic applications because of its low solubility, poor photostability and susceptibility to colour change [9]. One approach that can be used to improve the solubility and bioavailability of carotenoids such as b-carotene is to incorporate them in the fine particles of oil-in water (O/W) emulsions.

Garti and coworkers [10, 11], for example, prepared food-grade microemulsions containing carotenoids with considerable success.

During the past two decades, nanotechnology has emerged as one of the most interesting and promising research fields [12, 13].

The technology offers the potential to significantly improve the solubility and bioavailability of many functional ingredients including carotenoids, polyunsaturated fatty acids, phytosterols and numerous other compounds.

Nanoemulsions covering the size range 50–200 nm have characteristic properties which can have important application in the personal care, cosmetics and health science fields because of the following: 1 Small droplet size which reduces the adverse effect of gravity on the emulsion compared to systems with larger particle sizes and thus reduces the likelihood of creaming or sedimentation.

Correspondence: Dong-myung Kim, Cosmetic R&D Center, 183-5,

Dodang-dong, Wonmi-gu, Bucheon-si, Gyeonggi-do, South Korea. Tel.: 032-682-3000 (extn. 200); fax: 032-677-2323; e-mail a6093@Kolmar. co.kr

International Journal of Cosmetic Science, 2012, 34, 64–73 doi: 10.1111/j.1468-2494.2011.00682.x ª 2011 The Authors