Xilogel is a Tamarindus indica polysaccharide endowed with remarkable filming and hydrating properties. It has been extremely well characterised as a branched high molecular weight (ca 650,000 Da) xyloglucan, capable of forming viscous gels with an excellent sensory feeling.
Preliminary evidence of film formation, improvement of skin elasticity, amelioration of trans-epidermal water loss and micro-roughness reduction was obtained. Capitalising on these observations, we have investigated the cosmetic potential of Xilogel for its short and long term moisturising effect, anti-ageing activity, elasticising and skin densifying properties on 20 volunteers; it has been compared to the challenging positive reference sodium hyaluronate (1.1 MioDa to 1.8 MioDa). In addition to this, further evaluations have been carried out in vitro on senescent cells, validating Xilogel as an inhibitor of ?-galactosidase (typically overexpressed in aged keratinocytes) and an improver of filaggrin synthesis, a protein crucial in maintaining skin hydration.
Tamarind is considered as one of the most beautiful trees growing in the South- East of Asia, and is also an edible plant: its young pods are used both for nutrition and to manufacture spices.1 Traditionally used in the Ayurvedic medicine even today, its use as a laxative dates back to the 1500s even in Western countries. The seed of tamarind has a high content of polysaccharides among which the most abundant is a branched polysaccharide of a cellulose-type backbone (?-(1-4)Dglucose) carrying xylose and galactoxylose substituents (Fig. 1). This polysaccharide has been extremely well characterised (the polydispersion index being very limited, i.e. the number of molecules largely differing from the fixed molecular weight), and its use in cosmetic formulations has been assessed in terms of skin hydration, elasticity, roughness and density on healthy volunteers. Additionally, Xilogel has shown to impart a unique sensoriality to cosmetic formulations, a smooth running spreadability that is perceivable at concentrations as low as 0.1%. In the present study, the cosmetic efficacy of Xilogel (now referred to as ‘the moisturising active’) has been compared with that of sodium hyaluronate, employed at the same percentage (0.5%) in the same cosmetic formulation (either containing the moisturising active or sodium hyaluronate). Hyaluronic acid is an endogenous glycosaminoglycan of the extracellular matrix; its structure makes it highly effective in retaining water and plays an important role in maintaining the appropriate hydration for the transportation of nutrients. The topical application of hyaluronic acid or its derivatives as sodium hyaluronate provide an effective cutaneous hydration.2 Additionally, the effect of the moisturising active has also been evaluated in vitro by assessing the activity of the beta-galactosidase enzyme, a characteristic marker in senescent cells. Also, the regulation of filaggrin, a protein considered as a biomarker of hydration, has been investigated.
Study protocol and results
Twenty female volunteers aged 35-60 years were selected for the clinical trial. They were requested not to use other products on the tested area, to avoid intentional UV exposure and to refrain from washing their face three hours prior to measurements. The volunteers were required to apply the moisturising active – containing emulsion on one half of the face, the sodium hyaluronate – containing formulation on the other half, in a single blind manner, twice daily for four weeks. At the beginning (T0) and at the end of the treatment (Tf, after four weeks) instrumental measurements of skin hydration, skin elasticity, roughness and skin density/echogenicity were performed on each half face. An additional measurement of skin hydration was performed after 30 minutes from the first application of a controlled dose of product (2 mg/cm2). The composition of the topical formulation is shown in Table 1.
Skin hydration was measured by the means of a Corneometer CM 825 (Courage & Khazaka, Germany), which express skin moisture through the widely known corneometric units (ranging 0-150).
Skin elasticity was measured by means of a Cutometer SEM 575 (Courage & Khazaka, Germany), assessing the vertical deformation of the skin when sucked into the opening of a measuring probe. The resulting parameters refer to:
• R0 as maximal skin deformation.
• R2 as overall elasticity.
• R6 as viscoelastic ratio.
Skin roughness was measured by recording 3D images of the skin structure (GFM, Germany) allowing the measurement of the parameters:
• Sa as average roughness.
• Sz as average maximum roughness.
Skin density Skin density was measured by means of an Ultrasound Scanner Dermascan C Ver 3 (Cortex Technology, Denmark) expressing the changes of intensity of the reflected signal through colour changes according to the following scale: white > yellow > red > green > blue > black. In terms of statistical analysis, the data have been analysed by means of the Student’s t-test for paired data, the results being considered statistically significant when the P value was ?0.05.
In vitro studies
According to a preliminary MTT test, the product results show the moisturising active not to modify cellular vitality in terms of cells morphology and metabolism. The MTT test is considered as a preliminary indication before conducting further in vitro investigations. The activity of beta-galactosidase, which is an enzyme considered a marker of ageing (with an increased betagalactosidase activity in senescent cells), has been evaluated on aged keratinocytes and expressed as arbitrary fluorescence units (AU). Beta-galactosidase is a lisosomial enzyme expressed both in aged and non-aged cells, showing an optimal activity at pH = 4. However, at a pH of around 6, the expression of betagalactosidase is evident only in aged keratinocytes and fibroblasts. The expression of filaggrin has been evaluated by immunocytochemistry (using a monoclonal anti-filaggrin antibody and, afterwards, the secondary fluorescent goat anti-mouse antibody). The analytical software NIS elements 3.10 has then calculated arbitrary fluorescent units again. Filaggrin expression has shown a tendential increase by 17%.
Clinical study (ISPE report 31/11/01-02 (2011))
The moisturising active, already 30 minutes after the application, induces a significant increase in skin hydration (+59%), higher than the improvement obtained with the formulation containing sodium hyaluronate (+55%), with a statistically significant difference (P=0.001). The hydration effect is maintained both by the moisturising active and sodium hyaluronate, and, after the repeated applications during the four weeks of the study, the skin hydration improved in a comparable way (36% and 37% respectively). In the area treated with the moisturising active-containing formulation, an improvement of cutaneous elasticity parameters was observed: variations of biological elasticity (R2), maximal deformation (R0) and viscoelastic ratio (R6) resulted highly significant and were comparable to the benchmark (with an almost 20% increase). The moisturising active has reduced the roughness parameters Ra (mean roughness) and Rz (maximum roughness) by 21% and 28% respectively, with the effect once again comparable to the benchmark. The difference is also perceivable in some representative 3D images (see Fig. 2).
Due to its chemicophysical characteristics, the moisturising active is suitable to be incorporated into different types of formulations. It has a high compatibility both in the traditional O/W and W/O systems and water-based gels, where it also provides a stabilising and thickening effect, and also in siliconcontaining systems.
The present study has compared the cosmetic effect of a formulation containing the moisturising active and a formulation containing sodium hyaluronate as positive reference, both used at the same concentration of 0.5%. Similarly to sodium hyaluronate, after four weeks of application the moisturising active improves skin hydration (36%), skin elasticity (19%), reduces skin roughness (28%) and increased skin density (8%). No significant differences are observed between the two tested active ingredients. The main difference observed between the moisturising active and sodium hyaluronate was observed 30 minutes after the application, when the moisturising active induced a higher increase in skin hydration compared to the positive reference. Also, the two ingredients have a different structure and a different molecular weight, the moisturising active being a branched polysaccharide weighing 650 kDa while hyaluronic acid is a glycosaminoglycan with a molecular weight ranging between 1.1 MioDa and 1.8 MioDa. The branched structure of the xyloglucan in the moisturising active induced a high water retention capacity. All the other improvements suggest that, due to an improved hydration of skin cells, elasticity is boosted as well as skin roughness appears less evident. Additionally, the skin density improvement parameter may also be explained by a better homeostatic balance of dermis cells. Finally, the skin-feel is once again quite different being the touch provided by the moisturising active extremely silky and smooth-running. Besides the cosmetic properties investigated in the current study, it is worth mentioning that the polysaccharides obtained from the seed of tamarind have been reported to prevent the suppression of the immune-response and the IL-10 production induced by UV irradiation in animal models,3,4 qualifying Xilogel as an ingredient to be used in sun care products as well.
1 El-Siddig et al. Tamarind, Tamarindus indica, International Centre for Underutilised Crops, Southampton, revised edition (2006). 2 Rigano L, Andolfatto C, Stucchi L, Bosco M. Esteri butirrici dell’acido ialuronico. Derivati ialuronici con efficacia anti-aging. Cosm Technol 2010; 13 (6): 15-21. 3 Strickland FM et al. Inhibition of UV-induced suppression and interleukin-10 production by plant oligosaccharides and polysaccharides. Photochem Photobiol 1999; 69 (2): 141-7. 4 Strickland FM et al. Natural products as aids for protecting the skin’s immune system against UV damage. Cutis 2004; 74 (Suppl 5): 24-28.