External lipid function in ethnic hairs

Abstract

Objective The main aim of this study is to characterize the external lipids of different ethnic hairs and to study the contribution of the exogenous lipids on their physicochemical properties. Methods On the extraction procedure, sebaceous lipids from the exterior of the fiber are removed. The influence of those free lipids on the hair properties, such as contact angle, mechanical characteristics, and sorption of water, will be evaluated to determine permeation characteristics of the keratin fibers. Relationship with lipid order was also determined by infrared spectroscopy (IR). Results Lipid extraction indicates the greatest amount of total lipids for African hair. Caucasian lipid extracts present the higher melting point and phase transition temperatures. This could be related to higher hydration and lower diffusion coefficient of the Caucasian fibers. A decrease in moisture was found in the lipid‐extracted fibers. This diminution of the maximum water regain in all cases could be due to a higher water desorption. IR results indicate that Caucasian and moreover African native fibers present the most quantity of lipids, and the similar frequency of all fibers indicates a lamellar/orthorhombic order arrangement. Conclusion The hexane/tert‐butanol extraction was demonstrated to modify not only cuticular but also cortex lipids. Exogenous lipid depletion in all fibers indicates a less water content and higher water desorption. However, lipid depleted Caucasian fibers presents an increase in the lipid order which could be related to the different saturation of the lipid extract and its improvement in breaking tenacity.

<p>Asian Hair: A Review of Structures, Properties, and Distinctive Disorders</p>

“…All three hair origins similarly show a smaller amount of lipids in the cortex compared with the cuticles. 7 Asian hair demonstrates a greater amount of integral lipids than the other two ethnic hairs, which exhibit lesser damage to ultraviolet irradiation. In addition, Takahashi and Yoshida detected glycoside-like lipids (particularly N-acetyl glycoside) in Japanese female hairs at the interface between the cuticle and the cortex producing an adhesive effect between the two layers.…”

“…The comparisons of hair characteristics among the three major ethnic groups are summarized in Table 1. [2][3][4][5][6][7][8] Correspondence: Poonkiat Suchonwanit Email poonkiat@hotmail.com…”

“…External lipids, including sterol esters and squalene, are known to arise from the surface sebaceous lipids. 7,43 Experimental results showed that among the three ethnicities, African hair has the largest amount of total hair lipid extractions, followed by Caucasian and Asian hairs. 43 The lipids in African hair mainly come from the sebaceous lipids, and those in Asian and Caucasian hairs mainly come from the internal lipids.…”

“…13 With regard to percentages over weight of whole fibers, contents of FFA, sterol, and polar lipids are the highest in African hair. 7,13 The internal lipids were postulated to intercalate the keratin dimers and influence the organization of keratin fibers, which may lead to various hair morphologies. 13,14 In relation to the external lipids, African fiber presents the greatest proportion of apolar lipids, and Asian and Caucasian extracts show a higher amount of FFA and polar lipids.…”

“…13,14 In relation to the external lipids, African fiber presents the greatest proportion of apolar lipids, and Asian and Caucasian extracts show a higher amount of FFA and polar lipids. 7 The high amount of apolar lipids with hydrophobic property in African fiber is associated with lesser swelling in water as it blocks the entrance of water into the hair. 3,13 Integral hair lipids located in the CMC of hair cuticle layers are accountable for hair integrity, maintenance of hydrophobicity, moisture, and hair stiffness.…”