A new hair-conditioning agent, N-[3-(dimethylamino)propyl]docosanamide (APA-22) hydrochloric acid salt (APA-22 HCl), has excellent solubility in water with a solubility limit over 10-times larger than that of other APA hydrochloric salts with shorter alkyl chain lengths. The physicochemical characteristics of APA-22 HCl were studied at 25°C by using equilibrium surface tension (γ), solubilization of an oil-soluble dye, steady-state fluorescence, and chloride ion selective electrode techniques. The APA-22 HCl salt is considered to form an aggregate at a concentration, C₁, which is about twice the concentration of the solubility limit of APAs with shorter alkyl chains. At a higher concentration, C₂, the aggregates of APA-22 HCl start forming another kind of aggregate, which is able to solubilize oil-soluble materials. That is, C₁ is considered to represent the critical aggregation concentration (cac) and C₂ a morphology transition. In the concentration region between C₁ and C₂ the solutions are seemingly transparent whereas at above C₂ they appear bluish or translucent. Since the Krafft point of APA-22 HCl is 55°C, all the solutions, including the aggregates, are thought to exist in metastable states. Notably, however, these metastable solutions do not change significantly over a few months. The excellent solubility of APA-22 HCl in water is considered to be a result of this unique stepwise aggregation with increasing concentration.

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Cationic surfactant is a chemical substance used in hair conditioner, fabric softener and other household products. By investigating the relationship between the aquatic toxicity and the chemical structures of two types of mono alkyl cationic surfactants, alkyl trimethylammonium salts and alkyl dimethylamine salts, we have found that the C22 alkyl chain length is effective to reduce the toxicity. Besides, we have recognized that the amidopropyl functional group contributes to the enhanced biodegradability by investigating the biodegradation trend of (alkylamidopropyl)dimethylamine salt (alkyl chain length: C18). Based on these findings, we have developed mono alkyl cationic surfactant called APA-22, N-[3-(dimethylamino)propyl]docosanamide salt. APA-22 is formed by the C22 alkyl chain, amidopropyl functional group and di-methyltertiary amine group. We evaluated the aerobic and anaerobic biodegradability of APA-22 by two standard methods (OECD Test Guideline 301B and ECETOC technical document No.28) and found that this substance was degraded rapidly in both conditions. The toxicity to algae, invertebrate and fish of this substance are evaluated by using OECD Test Guideline 201, 202 and 203, respectively. All acute toxicity values are >1 mg/L, which indicates that environmental toxicity of this substance is relatively less toxic to aquatic organism. In addition, we estimated the biodegradation pathway of APA-22 and observed the complete disappearance of APA-22 and its intermediates during the test periods. Based on the environmental data provided above, we concluded that APA22 is more compatible with the aquatic environment compared to other cationic surfactants with mono long alkyl chain.

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Bovine serum albumin (BSA) was employed as a model protein emulsifier to conjugate with aldohexose (D-glucose (Glc) or D-allose (All)) and sugar fatty acid ester (6-O-octanoyl-D-glucose (GlcC8)) through the Maillard reaction. It was found during the reaction that rate of decrease of free amino groups in BSA was almost the same for the BSA-sugar mixtures whereas browning and protein aggregation developed in the following order: Glc < All < GlcC8. It was thought that the rate of degradation of the Amadori compound could have been influenced by the OH-group stereochemistry at the C3 position of aldohexose, while denaturation of BSA by GlcC8 enhanced the browning and protein aggregation. To understand the emulsifying ability of the BSA-sugar conjugates, hexadecane-water interfacial tension and the oil droplet size of emulsions prepared by homogenizing hexadecane and aqueous solution of the conjugates were examined. BSA-GlcC8 showed greater improvement in interfacial and emulsifying activity than did BSA-Glc and -All. However, no improvement in emulsion stability was observed for any of the BSA-sugar conjugates, suggesting the weakness of the film formed at the oil droplet interface.

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Mannosylerythritol lipids (MELs) are one of the most promising glycolipid biosurfactants known because of their multifunctionality and biocompatibility. The search for novel producers of MELs was undertaken based on the analysis of ribosomal DNA sequences on basidiomycetous yeasts. The bermuda grass smut fungus Ustilago cynodontis NBRC 7530, which taxonomically relates to Pseudozyma shanxiensis known as a MEL-C producer, was found to accumulate glycolipids in the cultured medium. Under a shake flask culture with soybean oil, the amount of the glycolipids was 1.4 g/L for 7 days at 25°C. As a result of the structural characterization, the main glycolipids was identified as 4-O-[(4′-O-acetyl-3′-O-alka(e)noyl-2′-O-butanoyl)-β-D-mannopyranosyl]-D-erythritol, and the major fatty acids were C₁₄ and C₁₆ ones. The glycolipid was highly hydrophilic MEL-C, and very similar to those produced by P. shanxiensis. The fungi of the genus Ustilago are thus likely to be potential producers of MELs as well as the yeasts of the genus Pseudozyma.

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Mannosylerythritol lipids (MELs) are one of the most promising biosurfactants known, because of their multifunctionality and biocompatibility. In order to attain an efficient production of MELs, Pseudozyma parantarctica JCM 11752^T, which is a newly identified strain of the genus, was examined for the productivity of MELs at different culture conditions. The yeast strain showed significant cell growth and production of di-acylated MELs even at 36°C. In contrast, on conventional high-level MEL producers including P. rugulosa, the MEL yield considerably decreased with an increase of the cultivation temperature at over 30°C. On P. parantarctica, soybean oil and sodium nitrate were the best carbon and nitrogen sources, respectively. Under the optimal conditions on a shake-flask culture at 34°C, the amount of di-acylated MELs reached over 100 g/L by intermittent feeding of only soybean oil.
     Interestingly, the yeast strain produced tri-acylated MELs as well as di-acylated ones when grown on the medium containing higher soybean oil concentrations than 8% (vol/vol). The production of tri-acylated MELs was significantly accelerated at between 34 and 36°C. With 20 % (vol/vol) of soybean oil at 34°C, the yield of tri-acylated MELs reached 22.7 g/L. The extracellular lipase activity considerably depended on the culture temperature, and became the maximum at 34°C; this would bring the accelerated production of tri-acylated MELs. Accordingly, the present strain of P. parantarctica provided high efficiency in MEL production at elevated temperatures compared to conventional MEL producers, and would thus be highly advantageous for the commercial production of the promising biosurfactants.

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We have developed various kinds of ultrafine emulsifying methods using random copolymer of polyoxyethylene (POE) / polyoxypropylene (POP) dimethyl ether [EPDME]. Among ultrafine emulsions made by these methods, it was revealed that an O/W type emulsion, which had prepared with EPDME, sterol surfactant, and polar oils, had a unique structure that had a lamellar structure on the surface of emulsified particles. To clarify the character of the particles and the mechanism of the emulsification, investigation using small angle X-ray scattering (SAXS) measurement and the phase diagram of the emulsion system was done. FF-TEM observation indicated that a few lamellar layers were deposited from the oily ingredients on the surface of the emulsified particle. It was also presumed that the lamellar structure was formed with sterol surfactant and polar oil. The phase diagram analysis suggested that EPDME could form emulsified particles having lamellar structure on the surface of the particle with hydrophilic sterol surfactant in polar oils.

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To assess the antioxidative role of vitamin E (VE) in a mouse model of severe VE deficiency by using biomarkers, α-tocopherol transfer protein (α-TTP^-/-)-knockout mice were maintained on a VE-deficient diet for 28 weeks [KO group, n = 6]. Wild-type C57BL/6 mice were maintained on a diet containing 0.002% α-tocopherol [WT group, n = 6]. The animals were housed individually in a metabolic cage from the age of 9 weeks (Week 0) to 27 weeks. Urine was collected every week, and the levels of total hydroxyoctadecadienoic acid (tHODE), 7-hydroxycholesterol (t7-OHCh), and 8-iso-prostaglandin F_2α(t8-isoPGF_2α), which are biomarkers for lipid peroxidation, were measured by gas chromatography (GC)-mass spectrometry. From the age of 21 weeks (Week 12), three mice in each group were provided drinking water containing the water-soluble radical initiator 2,2′-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (AIPH) until the end of the study (Week 19). Blood and tissue samples were collected, and the levels of the abovementioned biomarkers therein were assessed. AIPH consumption clearly elevated the plasma and erythrocyte levels of tHODE and t8-isoPGF_2α in both the WT and KO groups except for the erythrocyte level of tHODE in the WT group. Furthermore, this elevation was more prominent in the KO group than in the WT group. Interestingly, AIPH consumption reduced the stereoisomer ratio of HODE (ZE/EE), which is reflective of the efficacy of a compound as an antioxidant in vivo; this suggests that free radical-mediated oxidation reduces the antioxidant capacity in vivo. The urine levels of tHODE, t7-OHCh, and t8-isoPGF_2α tended to increase with AIPH consumption, but these individual levels fluctuated. It was clearly demonstrated by the proposed biomarkers that maintaining α-TTP^-/- mice on a VE-deficient diet results in a severe VE deficiency and promotes lipid peroxidation.

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