Compendium of the most significant studies with reference to properties, intake, effects.

Kato S, Aoshima H, Saitoh Y, Miwa N. Biological safety of liposome-fullerene consisting of hydrogenated lecithin, glycine soja sterols, and fullerene-C60 upon photocytotoxicity and bacterial reverse mutagenicity. Toxicol Ind Health. 2009 Apr;25(3):197-203. doi: 10.1177/0748233709106186. 

Abstract Various water-soluble derivatives of fullerene-C60 (C60) have been developed as detoxifiers for reactive oxygen species (ROS), whereas C60 incorporated in liposome (Lpsm) has not been reported yet. We prepared the liposome-fullerene (0.2% aqueous phase, Lpsm-Flln) which was composed of hydrogenated lecithin, glycine soja (soybean) sterols, and C60 in the weight ratio of 89.7:10:0.3, then examined the photocytotoxicity and bacterial reverse mutagenicity, as comparing with the Lpsm containing no C60. Photocytoxicity of Lpsm-Flln or Lpsm was examined using Balb/3T3 fibroblastic cells at graded doses of 0.49-1000 microg/mL under the condition of UVA- or sham-irradiation. The cells were irradiated with UVA (5 J/cm2, 320-400 nm, lambda max = 360 nm) at room temperature for 50 min. The resultant cell viability (% of control) did not decrease dose-dependently to 50% or less regardless of the UVA-irradiation. These results show that Lpsm-Flln or Lpsm does not possess photocytotoxicity to Balb/3T3 fibroblasts, and Lpsm-Flln may not exert a UVA-catalytic ROS-increasing action. A possibility for the reverse mutation by Lpsm-Flln or Lpsm was examined on four histidine-demanding strains of Salmonella typhimurium and a tryptophan-demanding strain of Escherichia coli. As for the dosages of Lpsm-Flln or Lpsm (313-5000 microg/plate), the dose-dependency of the number of reverse mutation colonies of each strain did not show a twice or more difference versus the negative control regardless of the metabolic activation, and, in contrast, marked differences for five positive controls (sodium azide, N-ethyl-N'-nitro-N-nitrosoguanidine, 2-nitrofluorene, 9-aminoacridine, and 2-aminoanthracene). The growth inhibition of bacterial strains and the deposition of Lpsm-Flln or Lpsm were not found. As a result, the bacterial reverse mutagenicity of Lpsm-Flln or Lpsm was judged to be negative under the conditions of this test. Thus, Lpsm-Flln and Lpsm may not give any significant biological toxic effects, such as photocytotoxicity and bacterial reverse mutagenicity.

Bae, D. H., Shin, J. S., Shin, G. S., Jin, F. L., & Park, S. J. (2009). Effect of lecithin on dermal safety of nanoemulsion prepared from hydrogenated lecithin and silicone oil. Bulletin of the Korean Chemical Society, 30(4), 821-824.

Abstract In this study, a hydrogenated lecithin-containing nanoemulsion was prepared from hydrogenated lecithin and silicone oil. Tween-60 and liquid paraffin, widely known emulsifiers, were used as standard substances, and high shear was produced by utilizing a high shear homogenizer and microfluidizer. The properties of the nanoemulsion prepared with hydrogenated lecithin were evaluated by measuring interfacial tension, dynamic interfacial tension, droplet size, zeta-potential, friction force, skin surface hygrometery, and dermal safety. The interfacial tension of lecinol S10/silicone oil was lower than that of lecinol S10/liquid paraffin. The nanoemulsion prepared from hydrogenated lecithin shows lower zeta-potential, skin surface hygrometery, and friction force compared with a general emulsion. The silicone nanoemulsion prepared from hydrogenated lecithin showed a zero value in the patch test and thus exhibits high dermal safety.

Fiume Z. Final report on the safety assessment of Lecithin and Hydrogenated Lecithin. Int J Toxicol. 2001;20 Suppl 1:21-45. doi: 10.1080/109158101750300937. 

Abstract Lecithin is a naturally occurring mixture of the diglycerides of stearic, palmitic, and oleic acids, linked to the choline ester of phosphoric acid, commonly called phosphatidylcholine. Hydrogenated Lecithin is the product of controlled hydrogenation of Lecithin. Bilayers of these phospholipids in water may form liposomes, a spherical structure in which the acyl chains are inside and not exposed to the aqueous phase. Lecithin and Hydrogenated Lecithin are used in a large number of cosmetic formulations as skin conditioning agents-miscellaneous and as surfactant-emulsifying agents. Hydrogenated Lecithin is also used as a suspending agent-nonsurfactant. Historical data on concentration of use of Lecithin reveals that 0.1% to 1.0% is the concentration range most frequently seen, with concentrations up to 50% reported for two moisturizing products. A solution of 65% Lecithin is currently reported to be used at concentrations up to 3% in cosmetics. Nonocclusive application of Lecithin-containing liposomes to murine skin resulted in 30% penetration to the subdermis. In piglet skin, the same application resulted in 99% accumulating in the stratum corneum. In general, liposomes are considered effective in capturing other compounds inside their spherical structure and delivering any such captured compound through the skin barrier. As a result, caution should be exhibited in formulating cosmetic products that contain these ingredients in combination with other ingredients whose safety is based on their lack of absorption or where dermal absorption is a concern. Lecithin is virtually nontoxic in acute oral studies, short-term oral studies, and subchronic dermal studies in animals. Lecithin is not a reproductive toxicant, nor is it mutagenic in several assays. In an oral carcinogenicity study, brain neoplasms were found in mice exposed to Lecithin. In a subcutaneous carcinogenicity study, no neoplasms were found in mice and rats exposed to Lecithin. Adverse reactions to Lecithin in a metered-dose inhaler have been reported. Lecithin and Hydrogenated Lecithin were generally nonirritating and nonsensitizing in animal and human skin. Based on the available data, Lecithin and Hydrogenated Lecithin are safe as used in rinse-off cosmetic products; they may be safely used in leave-on products at concentrations up to 15%, the highest concentration tested in clinical irritation and sensitization studies; but the safety of use could not be substantiated in cosmetic products likely to be inhaled. Because of the possibility of formation of nitrosamines, these ingredients should not be used in cosmetic products in which N-nitroso compounds may be formed.

Cho, W. G., Yang, H. J., & Park, S. N. (2008). Ostwald Ripening in Hydrogenated Lecithin-stabilized Oil-in-Water Nano-emulsions. Journal of the Society of Cosmetic Scientists of Korea, 34(1), 9-14.

Abstract Formation of oil-in-water nano-emulsions has been studied in oil/hydrogenated lecithin/water systems by two shear different instrument. The influence of surfactant concentration on nano-emulsion droplet size and stability has been studied. Droplet size was determined by dynamic light scattering, and nano-emulsion stability was evaluated by measuring the variation of droplet size as a function of time. The results obtained showed that the breakdown process of nano-emulsions studied could be attributed to Ostwald ripening. An increase of nano-emulsion instability with increase in surfactant concentration was found in the droplet size in the range of 100~200nm, however, an decrease of instability was found in the droplet size in the range of 300~400nm.

Kim, I. Y., Lee, J. D., Ryoo, H. C., & Zhoh, C. K. (2004). Formation of liquid crystalline with hydrogenated lecithin and its effectiveness. Journal of the Society of Cosmetic Scientists of Korea, 30(2), 159-165.

Abstract This study described about method that forms liquid crystal gel (LCG) by main ingredient with hydrogenated lechin (HL) in O/W emulsion system. Result of stability test is as following with most suitable LCG's composition. Composition of LCG is as following, to form liquid crystal, an emulsifier used 4.0wt% of cetostearyl alcohol (CA) by 4.0wt% of HL as a booster. Moisturizers contained 2wt% of glycerin and 3.0wt% of 1,3-butylene glycol (1,3-BG). Suitable emollients used 3.0wt% of cyclomethicone, 3.0wt% of isononyl isononanoate (ININ), 3.0wt% of cerpric/carprylic triglycerides (CCTG), 3.0wt% of macademia nut oil (MNO) in liquid crystal gel formation. On optimum conditions of LCG formation, the pHs were formed all well under acidity or alkalinity conditions (pH=4.0-11.0). Considering safety of skin, pH was the most suitable 6.0±1.0 ranges. The stable hardness of LCG formation appeared best in 32 dyne/cm². Particle of LCG is forming size of 1-20μm range, and confirmed that the most excellent LCG is formed in 1-6μm range. According to result that observe shape of LCG with optical or polarization microscope, LCG could was formed, and confirmed that is forming multi -layer lamellar type structure around the LCG. Moisturizing effect measured clinical test about 20 volunteers. As a result, moisturizing effect of LCG compares to placebo cream was increased 36.6%. This could predicted that polyol group is appeared the actual state because is adsorbed much to round liquid crystal droplets to multi-lamellar layer's hydrophilic group. It could predicted that polyol group is vast quantity present phase that appear mixed because is adsorbed to round liquid crystal to multi-lamellar layer's hydrophilic group. This LCG formation theory may contribute greatly in cosmetics and pharmacy industry development.

NATSUKI, R., MORITA, Y., OSAWA, S., & TAKEDA, Y. (1996). Effects of liposome size on penetration of dl-tocopherol acetate into skin. Biological and Pharmaceutical Bulletin, 19(5), 758-761.

Abstract. Liposomes were prepared from hydrogenated lecithin (H-PC) by sonication (S) or injection (I) of H-PC dissolved in ethanol containing dl-tocopherol acetate (VEA). The effects of liposomes on the dermal absorption of VEA were studied. The particle diameter of S-liposomes was smaller than that of I-liposomes. The penetration of liposomal H-PC into the skin was much higher for S-liposomes than for I-liposomes 30 min after application to the arms of healthy human volunteers and also to hairless rat back skin. The penetration of 14C-VEA into hairless rat back skin was higher from the liposomes than from free VEA, and the 14C-VEA penetration was higher from S-liposomes than from I-liposomes. 3H-Dipalmitoylphosphatidylcholine and 14C-VEA, which had been entrapped in liposomes, were not detected in plasma. H-PC inhibited the peroxidation of skin lipids. H-PC enhanced the penetration of VEA into the skin, but the degree of enhancement depended on the size of the liposomes, indicating that this liposomal characteristic was an important factor in dermal absorption and/or penetration.

Kim, I. Y., Zhoh, C. K., & Ryoo, H. C. (2003). Formation of Provitamin-$ B_5 $ Liquid Crystal with Hydrogenated Lecithin and Its Effectiveness of Moisturizing Activity. Journal of the Korean Applied Science and Technology, 20(2), 101-109.

Abstract. Provitamin B5 liquid crystal (PVB5-LC) was the new emulsion system to enhance moisturizing activity on the skin. In this study, it should be mentioned that PVB5-LC could be prepared with the main compound of hydrogenated lecithin (HL) in oil-in water (O/W) emulsion. The key ingredient of humectants was contained 2% of provitamin B5(PVB5) into the PVB5-LC. The best suitable compositions of PVB5-LC were made from 4.0 wt% of HL, 4.0 wt% of cetostearyl alcohol (CSA) as emulsifier and gelling agent, 3.0 wt% of 1,3-butylene glycol (1,3-BG) and 2.0 wt% of glycerin as moisturizers, 3.0 wt% of cyclomethicone (CMC), 3.0 wt% of isononanoate (ININ), 3.0 wt% of capric/caprylic triglyceride (CCTG), 3.0 wt% of macadamia nut oil (MNO) as emollients. As the analytical result of PVB5-LC, it could know that the distribution range of particle size was 0.14 to 12.37 m level (mean size 3.24 m). It was certified the multi lamellar phase around the droplet of liquid crystal when observed the droplet particles through a polarization microscope. And it clinically was tested the effectiveness of moisturizing activity (in-vivo) compared with control sample (O/W emulsion). The effectiveness of moisturizing activity of PVB5-LC with Skincon-200EX after 6 hours went up 49.0% (p<0.05, n=20) whereas the effectiveness of moisturizing activity of generally O/W emulsion cream was 25.7% (p<005, n=20). Also, in case of Comeometer CM-825, the moisturizing activity of PVB5-LC after 6 hours rose 36.6% (p<0.05, n=20) whereas the effectiveness of moisturizing activity of generally O/W emulsion cream was 10.8%. Therefore, it was known that the effectiveness moisturizing activity of PVB5-LC with HL was remarkably superior compared with O/W emulsion cream.