Hyaluronic Acid Butyric Esters for the Improvement of Skin Functionality

Feb 1, 2011 | Contact Author | By: Luigi Rigano and Chiara Andolfatto, Rigano Consulting and Development; and Luca Stucchi and Marco Bosco, SIGEA S.r.l.
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Title: Hyaluronic Acid Butyric Esters for the Improvement of Skin Functionality
elasticityx fibroblastsx anti-wrinklex moisturizationx sebum reductionx
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Keywords: elasticity | fibroblasts | anti-wrinkle | moisturization | sebum reduction

Abstract: The versatility of hyaluronic acid is connected to not only its size, but also to inherent opportunities within the molecule for multiple bonds and for the differentiated release of bound functional molecules. Here, ester bonds are used to introduce substitutes for the material’s alcohol groups, thus providing elasticizing, moisturizing and antiaging benefits for skin care.

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L Rigano, C Andolfatto, L Stucchi and M Bosco, Hyaluronic Acid Butyric Esters for the Improvement of Skin Functionality, Cosm & Toil 126(2) 104 (2011)

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The word hyaluronic is derived from the Greek hyalos meaning “glass” or “transparent” and refers to the vitreous humor, the ocular tissue from which it was first isolated by Karl Meyer and colleagues in 1934. It was later located in many other animal tissues, i.e. synovial fluid, cartilage and the umbilical cord, where it has the same structure and biological activities, described in this article. Hyaluronic acid (HA)is a linear polysaccharide of high molecular weight that belongs to the family of mucopolysaccharides or glycosaminoglycans (GAGs), the physiological constituents of the dermal connective tissue in the extracellular matrix. In adult humans, the total amount of HA is equal to approximately 15 g, half of which is found in the skin.

At the skin compatible pH of 7, the carboxylic groups of HA are almost totally ionized, thus forming a polyanionic structure that imparts excellent hydro-coordinating properties in skin. This structure is mainly produced by skin keratinocytes and fibroblasts whose complete renewal cycle takes 2–4.5 days1—a much shorter time than the collagen cycle, which takes 60–70 days.2

Due to the functions HA serves in skin homeostasis, both its synthesis and degradation must be rapid and wellcontrolled by biological mechanisms. Indeed, it is an active physiological polymer that not only fulfills structure and filling functions, but also supplies water in the skin. In fact, due to its chemical structure, it is able to retain large amounts of water; for example, one gram of HA may act as a ligand for up to 6 L of water.3 Further, HA forms a scleroproteic sheath on fibrous protein, thus ensuring appropriate lubrication.

Similar to a biological sponge, HA resists compression and imparts structure to the dermis. This is due to its electrostatic interactions with collagen fibers, matrix proteins and other GAGs that form large-sized, “bottlebrushshaped” aggregates called proteoglycans. The structural organization of the extracellular matrix stabilizes the orientation of collagen fibers, preventing them from becoming too close and forming links among fibrils, in turn developing into insoluble collagen and toughening the skin, as occurs with age.

Finally, HA, fully surrounded by its hydration sphere, facilitates the extracellular transport of ions, solutes and metabolites, much like a chromatographic column. In addition, it affects the migration, differentiation, growth and adhesion of cells; angiogenesis; and control of the immune response.1, 3–6

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Table 1. Test Gels for the Described Studies

Table 1. Test Gels for the Described Studies

To assess the anti-wrinkle efficacy of HA ester butyrate from extended use, the authors used several noninvasive instruments to measure skin moisture, elasticity, sebum and roughness effects after the topical application of two gels employing the material at different concentrations (see Table 1, A and B) and two control gels containing HA and sodium salt (C), and HA and urea (D), respectively.

Table 2. Randomized Application Plan for the 24 Female Volunteers

Table 2. Randomized Application Plan for the 24 Female Volunteers

For a first set of tests, 24 female volunteers with an average age of 50 applied two test products to their faces, one on each side, twice daily for four weeks according to the randomized plan shown in Table 2; each formulation was thus used by 12 volunteers.

Table 3. Test emulsions with or without hyaluronic acid ester butyrate, used in the moisturizing and elasticizing efficacy tests

Table 3. Test emulsions with or without hyaluronic acid ester butyrate, used in the moisturizing and elasticizing efficacy tests

Tests of the emulsions containing 0.1% HA butyrate (see Table 3) showed the formulae to induce a remarkable and highly significant  increase in skin moisture values (p < 0.01), +52% and +44.4%, respectively. 34, 35 In addition, a highly significant increase (p < 0.01) in biological elasticity, R2, was noted, equal to + 15.6% and +23.1%, respectively. Comparison of the tested formulas with the placebo resulted in highly significant results throughout the tests (see Figure 8).

Figure 1. Changes in rate of hydrolysis of HA and HA butyric ester (HABut) when the amount of hyaluronidase enzyme varies

Figure 1. Changes in rate of hydrolysis of HA and HA butyric ester (HABut) when the amount of hyaluronidase enzyme varies

Indeed, its half-life is short (approx. 5 min) due to rapid metabolism and excretion (see Figure 1).

Figure 2. Synthesis of HA butyric esters

Figure 2. Synthesis of HA butyric esters

In addition, when the enzymatic concentration was equal to or higher than the concentration found in the bloodstream, HA and HA butyrate are rapidly de-polymerized (see Figure 2), indicating that modified HA would not remain in the bloodstream without being metabolized.

Figure 3. Changes in the parameter of maximum skin deformation, R0 , before (T0 ) and after (Tf ) treatment with the test gels; all variations were highly significant (p < 0.01).

Figure 3. Changes in the parameter of maximum skin deformation, R0 , before (T0 ) and after (Tf ) treatment with the test gels; all variations were highly significant (p < 0.01).

On the contrary, all gels induced a decrease in maximum skin stretchability R0, ranging between -32.2% and -40.8%, which is highly significant (p < 0.01). This means all the tested products made the skin firmer (see Figure 3.)

Figure 4. Changes in the biological elasticity parameter before and after treatment with the test gels

Figure 4. Changes in the biological elasticity parameter before and after treatment with the test gels

Changes in the biological elasticity parameter, R2 , before (T0 ) and after (Tf ) treatment with the test gels; the change with formula A is highly significant (p < 0.01), while for B, C and D, the differences are not statistically significant (p > 0.05). Moreover, the change induced by A was significantly different (p < 0.05) from that induced by D.

Figure 5. Changes in the skin elasticity parameter before and after treatment with gels

Figure 5. Changes in the skin elasticity parameter before and after treatment with gels

Changes in the skin elasticity parameter, R2 , before (T0 ) and after (Tf ) treatment with gels A and B (n = 20); formula A produced a highly statistically significant change (p < 0.01) while formula B produced a statistically significant change (p < 0.05).

Figure 6. Changes in sebum values before and after treatment with gels

Fig 6. Changes in sebum values before and after treatment with gels

Changes in sebum values (μg/cm2) before (T0 ) and after (Tf ) treatment with gels A and B (n = 20); only sample B was found to induce a statistically significant change (p < 0.05).

Figure 7. Changes in skin thickness before and after treatments with gels

Figure 7. Changes in skin thickness before and after treatments with gels

Changes in skin thickness (mm) before (T0 ) and after (Tf ) treatment with gels A and B (n = 20); only formula A induced a statistically significant change (p < 0.05).

Figure 8. Change in skin moisture and biologic elasticity before and after treatment with the antiaging cream

Figure 8. Change in skin moisture and biologic elasticity before and after treatment with the antiaging cream

Figure 8. Changes in skin moisture, expressed in corneometric units (CU), and biologic elasticity, R2 , before (T0 ) and after treatment with the antiaging cream, compared with the placebo treatment; the changes in the active cream were highly significant (p < 0.01) and significantly different (p < 0.01) from those induced by the placebo.

Footnotes (CT1102 Rigano)

a Model MCR301 rheometer plates are manufactured by Anton Paar.
b Finn Chambers are manufactured by Allergopharma SpA, Milano.
c The Corneometer CM 825 device is manufactured by Courage and Khazaka Instruments.
d The Cutometer SEM 575 device is manufactured by Courage and Khazaka Instruments.
e The Sebometer SM810 device is manufactured by Courage and Khazaka Instruments.
f The Dermascan C device is manufactured by Cortes Technology, Hadsuna, Denmark.
g The Chroma Meter CR-300 device is manufactured by Minolta.
h The Skin Surface Replicas and Image Analysis are manufactured by Quantilines-Monaderm.

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