Self‐Assembling Properties and Recovery Effects on Damaged Skin Cells of Chemically Synthesized Mannosylerythritol Lipids

Abstract

Mannosylerythritol lipids (MELs), which are one of the representative sugar‐based biosurfactants (BSs) produced by microorganisms, have attracted much attention in various fields in the sustainable development goals (SDGs) era. However, they are inseparable mixtures with respect to the chain length of the fatty acids. In this study, self‐assembling properties and structure‐activity relationship (SAR) studies of recovery effects on damaged skin cells using chemically synthesized MELs were investigated. It was revealed, for the first time, that synthetic and homogeneous MELs exhibited significant self‐assembling properties to form droplets or giant vesicles. In addition, a small difference in the length of the fatty acid chains of the MELs significantly affected their recovery effects on the damaged skin cells. MELs with medium or longer length alkyl chains exhibited much higher recovery effects than that of C18‐ceramide NP.

Synthesis of Mannosylerythritol Lipid Analogues and their Self‐Assembling Properties, Recovery Effects on Damaged Skin Cells, and Antibacterial Activity

“…It was found that compound 22 , which exhibited almost no recovery effect, did not show a CAC value in the tested concentration range due to its low surface activity. The CAC value for 23 , which exhibited a moderate recovery effect, was higher than that for MEL‐D 18 (1.7×10 −5 M) [7] at 2.7×10 −5 M due to its hydrophilicity. On the other hand, the CAC value for 24 , which exhibited an excellent recovery effect, was lower than that for 18 at 1.1×10 −5 M due to its hydrophobicity, suggesting that 24 was easily absorbed at lower concentrations into the intercellular spaces of the stratum corneum [16] .…”

“…When β‐GlcEL‐D 22 with all substituents in the equatorial position was used, micrometer‐sized solid aggregates containing hydrophobic Nile red were observed, probably because 22 was prone to interact intermolecularly (Figure 2a). In sharp contrast, when other MEL analogues 23 and 24 with at least one substituent in the axial position were used, it was found that Nile red was localized at the membrane boundary, and giant vesicles were spontaneously generated as for MEL‐D 18 [7] (Figure 2b and c). These results clearly indicated that slight differences in the steric configuration of a hydrophilic erythritol moiety and hydrophobic fatty acyl chains affect the ability to form vesicles.…”

“…A 2-ringed scattering pattern corresponding to the first and second Bragg peaks with d-spacing ratios of 1 : 1/2 was observed, indicating that 24 forms a lamella structure (Figure 5). The d-spacing for 24 (4.37 nm) is wider than that for 18 (4.22 nm), [7] suggesting that the hydration force for 24 may be higher than that for 18. [13] Taken together, these CAC and SAXS measurements that the differences in the anomeric configuration may affect hydrophobicity and hydration ability, enhancing the recovery effect of 24 on damaged cultured human skin cells.…”

“…However, since heterogeneity always exists in MELs obtained from microbial products, especially with respect to the chain length of the fatty acids, chemically synthesized homogeneous and structurally well‐defined MELs are required to carry out detailed structure‐activity relationship (SAR) studies. In this context, we recently accomplished the systematic and stereoselective synthesis of MELs 1 – 20 with different fatty acid chain lengths and different patterns of Ac groups at the C4’ and C6’ positions of the mannose moiety (MEL‐A 1 – 5 , MEL‐B 6 – 10 , MEL‐C 11 – 15 , and MEL‐D 16 – 20 ) (Figure 1), and conducted SAR studies of antibacterial activity, [6] self‐assembling properties, [7] and recovery effects on damaged skin cells [7] using chemically synthesized homogeneous MELs. The results of the antibacterial activity studies indicated that the structural differences of MEL‐A‐D and the length of the alkyl chain significantly affected their antibacterial activity, and MEL‐D with decanoyl groups (C10) 18 exhibited the most effective antibacterial activity against Gram‐positive bacteria including vancomycin‐resistant Enterococci (VRE).…”

Improvement of Oil Degradation and MEL Production in a Yeast Strain, <i>Pseudozyma tsukubaensis</i>, by Translation Elongation Factor 1 Promoter-driven Expression of a Lipase

“…In addition, they exhibit anti-bacterial, anti-cancer, and anti-oxidative activities 2−6) . One of the MEL producer Pseudozyma tsukubaensis produces a diastereomer type of MEL-B 7) at high levels (＞70 g/L from olive oil 8) ) and with the demonstrated ability to repair damaged skin and hair 6,9,10) . Accordingly, MEL-B has been commercialized in the cosmetics industry for over a decade.…”