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Hello, Hydration: Spinach Hydrogels Deliver Saturated Skin

Contact Author Nattaya Lourith and Mayuree Kanlayavattanakul, Mae Fah Luang University, Thailand
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Moisturizing or hydrating polysaccharides are derived from several natural sources. These botanical and edible biopolysaccharides are largely used to meet consumer demand for natural and sustainable cosmetic products. Polysaccharides are composed of multiple saccharides that form a large branched or unbranched chain. These polymers are constructed with simple sugar building blocks that are hydrated in an aqueous environment and create gel structures referred to as hydrogels or hydrocolloids.

Water is immobilized by insoluble polymers in this system, which can be used to moisturize skin. The moist gels are very compatible with biological tissues and are biodegradable, classifying them as biopolymers. They are inexpensive and vastly available from natural sources, which work to highlight their health benefits in cosmetic applications. Altogether, these factors strengthen consumer opinions of the safety and efficacy of biopolysaccharides.1, 2

Biopolysaccharides used in cosmetics are classified as either functional or active. Functional polysaccharides are deemed as such on the basis of their functions in the formulation; such as film-formers, gelling agents, thickeners, suspending agents, conditioners and emulsifiers. These actions primarily rely on the physicochemical properties of the biopolymer.

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On the other hand, active polysaccharides are classified as such based on the ability of the hydrogel or hydrocolloid to mobilize water upon application to skin, which is widely expected from cosmetic formulations. Moisturizing polysaccharides can therefore work as anti-aging ingredients by protecting skin while treating wrinkles. And again, since the actives are compatible with biological tissues and have a biodegradable nature, they can serve as key ingredients in sustainable cosmetics.

Ceylon Spinach

Ceylon spinach (Basella alba and B. rubra) is an important vegetable in many Asian recipes. B. alba has characteristic green leaves and stems, while B. rubra has red leaves and stems. B. alba grows faster and has greater active content than B. rubra. As such, it is cultivated at a higher volume.

B. alba has long been used as an Ayurvedic remedy for skin diseases and in traditional Thai medicine. Furthermore, this mucilaginous vegetable is a common addition to backyard gardens in north and northeastern Thailand, where it is cooked as a clean, organic soup.

In spite of its use in herbal remedies, ready availability and low cost, the potency of this green spinach polysaccharide for cosmetic applications has not been widely examined. The present work therefore explores its potential by first characterizing biopolysaccharide content, swelling capacity and hydration potential. In addition, the safety and efficacy of this biopolymer were evaluated in human volunteers, and findings were compared with those obtained previously for malva nut and okra polysaccharides.

Materials and Methods

The spinach polysaccharides were characterized as follows.

Preparation of the spinach polysaccharides: The fresh aerial part of green Ceylon spinach cultivated in Chiang Rai was cleaned and extracted via a patented method described elsewhere.3

Total polysaccharide content (TPC): The TPC content, for hydrating potential, was quantified using the phenol-sulfuric acid assay, and glucose was regarded as the standard. The result was expressed as μg glucose/g.3

Total tannin content (TTC): Total tannin content of the polysaccharide was determined by the Folin-Ciocalteu assay, and tannic acid was used as the standard and expressed as μg tannic acid/g.3, 4 This entity supports oil control in skin care applications.

Astringent activity: Astringent activity, also related to oil control, was measured by mixing the sample in ethanol with hemoglobin in phosphate buffer saline, followed by centrifugation. The supernatant was then analyzed in a comparison with tannic acid. Results were reported in mg tannic acid/g.3, 4

Swelling capacity and viscosity: The prepared polysaccharide extract was examined for swelling capacity in water and for viscosity; the percentage of swelling capacity and viscosity were reported in units of cps.3

Polysaccharide characterization: The polysaccharide content of the green spinach extract was confirmed by FT-IR analysis.3

Following characterization of the polysaccharides, in vitro and in vivo effects relevant to skin hydration potential were assessed.

Green Ceylon spinach polysaccharide extract meets cosmetic consumer preferences for naturally derived, safe and sustainably sourced cosmetic actives.

In vitro hydration and oil absorption capacities: Hydration and oil-absorption capacities were determined by mixing the polysaccharides with either water or olive oil in a centrifuge tube. After the supernatant was decanted, the residue weight was hydrated, centrifuged and recorded. The hydration and oil absorption capacities were calculated as the amount of water or olive oil retained by the pellet (g water/oil per g sample dry weight).4

Skin irritation and hydration: This study was delineated by the Declaration of Helsinki and Tokyo for humans, and was approved by the ethical committee of the Mae Fah Luang University (REH-59031) prior to volunteer enrollments and initiating the study. The green spinach polysaccharide extract (0.05% and 0.10% w/v in water) was preliminary assessed for skin irritation in 10 healthy Thai volunteers aged between 20-30 years old by means of a single-application, closed-patch test. Skin irritation severity was graded on a scale of 0-4. Observations were made immediately and at 24 hr, 48 hr and 72 hr following the removal of the patch test chambera. From this, a Mean Irritation Index (MII) was calculated, where a MII < 0.2 was interpreted as being non-irritating.

Thereafter, skin hydrating efficacy was evaluated in 22 volunteers and monitored by a corneometerb. Baseline skin hydration levels were recorded, followed by a single application of 0.05% and 0.10% spinach polysaccharide extract onto a different area of the skin in a randomized, single-blind procedure. Short-term skin hydrating efficacy was recorded, and changes in skin hydration percentages from the untreated, control skin were calculated.3, 4

Results and Discussion

As noted, green Ceylon spinach is widely grown in Thailand as a common vegetable. The spinach used for this study was grown in Chiang Rai, the northernmost area of Thailand, located in the Golden Triangle area. The spinach was collected from local farmers, and the physicochemical properties of the biopolysaccharide extract prepared from it were examined as described. Since total polysaccharide content and swelling/water absorption capacity (or hydration efficacy in vitro) are the physicochemical properties imparting skin hydration efficacy,1 these parameters were examined first.

TPC, swelling capacity and viscosity: As shown in Figure 1, the TPC for Ceylon spinach was 370 μg glucose/g, and the polysaccharide extract was 3.5-4.7% swelled in water, forming a thick, viscous solution (hydrogel). This swelling capacity increased with the hydrophilicity of the hydrogel network, whose behavior is related to viscosity. The vegetable polymer therefore demonstrated potential for use as a thickening or suspending agent in cosmetic products, in addition to possible applications for skin hydration.1, 4

Furthermore, although the TPC of the green spinach polysaccharide was less than that previously observed for malva nut,5 the spinach polysaccharide had greater swelling capacity and higher viscosity—green Ceylon spinach polysaccharide ranged from 1,515-1,565 cps, whereas malva nut polysaccharide was between 1,560-1,265 cps.5 This suggests a greater degree of skin-hydrating efficacy potential from the Ceylon spinach.

TTC, astringent activity and oil absorption: As noted, the TTC, astringency and oil-retention capacity of green Ceylon spinach also were demonstrated (see Figure 1). These relate to oil management and the control of greasiness in skin care.6, 7

Polysaccharide characterization: The polysaccharide nature of the Ceylon spinach extract was confirmed by FT-IR spectroscopy. Characteristic absorption bands of polysaccharide at 3,404 cm-1 (O-H), 2,943 cm-1 (C-H), 1,644 cm-1 (-COOR), 1,408 cm-1 (COO-), 1,310 cm-1 (O-H) and 1,246 cm-1 (C-O) were observed, with the carboxylate resonances at 1,644 and 1,408 cm-1 attributable to carbohydrate residues at 1,070 (CH2-O-CH2) and 1,039 cm-1 (CH2). Plus, a low energy C-O absorption in the fingerprint region (600 cm-1) confirmed that this green Ceylon spinach extract is a polysaccharide.4

The presence of numerous hydrogen bonds in green Ceylon spinach extract—to a greater degree than in malva nut hydrogel5—supports the higher viscosity and swelling capacities observed for the spinach polysaccharide. Thus, this green Ceylon spinach polysaccharide should offer better skin moisturization.

In vitro hydration efficacy: Hydration efficacy by means of water retention capacity was assessed in vitro as described. This property is an important criterion dictating the formation of hydrogels for cosmetic applications. The hydration efficacy of green Ceylon spinach polysaccharides shown in vitro (see Figure 1) is due to its high polysaccharide content, which governs water absorption levels.3, 4

Numerous hydrogen bonds in green Ceylon spinach extract support the polysaccharide's high viscosity and swelling capacities.

Safety and in vivo skin hydration efficacy: Although the preparation process for the green Ceylon spinach polysaccharide extract was modified in accordance with the method used for foods, preliminary skin irritation tests were conducted. The dermal safety of the biopolysaccharide extract was confirmed (MII = 0), as examined with water in parallel amid the same group of 10 volunteers.

Skin hydrating efficacy was then evaluated in 22 volunteers in vivo. A single application of the prepared green Ceylon spinach polysaccharide extract resulted in a better short-term skin hydration levels (7-28%) relative to the vehicle (water) and the control (untreated skin), as shown in Figure 2. Furthermore, the hydration efficacy of green Ceylon spinach polysaccharides proved to be superior over malva nut and okra polysaccharides,5, 8 previously assessed by a similar short-term efficacy evaluation (see Figure 3).

In these evaluations, malva nut was assessed at 0.5%, 0.75% and 1%, and the gum format exhibited better skin hydration than the untreated control at the longest period of 70 min; this effect would be governed by a different biopolysaccharide profile. However, the performance of malva nut was found to improve, depending on the form of dosage.5 Interestingly, the green Ceylon spinach polysaccharide was also more efficacious at hydrating skin than a commercially available okra polysaccharide formulated at 10%.

Conclusion

In the present work, green Ceylon spinach was proven to be a promising source for a safe and effective polysaccharide extract for skin hydration. Preparation of the vegetable polysaccharide via a previously described proprietary process3 suggests its feasibility on an industrial scale. Furthermore, the quality control and standardization protocols presented here allow for benchmarking of polysaccharide specifications with other commercially available polysaccharides for cosmetics. Indeed, the reported skin-hydrating activity and physicochemical properties of green Ceylon spinach polysaccharide will no doubt lead its successive applications in cosmetic formulations with variety of dosage forms.

The added value these findings provide is the potential to improve the quality of life for farmers growing this common crop. Altogether, green Ceylon spinach polysaccharide extract meets consumer preferences for naturally derived, safe and sustainably sourced cosmetic actives.

References

  1. Kanlayavattanakul, M., and Lourith, N. (2015). Biopolysaccharides for skin hydrating cosmetics. In: Polysaccharides (1867-1892). Cham, Switzerland: Springer.
  2. Kanlayavattanakul, M., and Lourith, N. (2015). An update on cutaneous aging treatment using herbs, J Cosmet Laser Ther, 17, 343-352.
  3. Kanlayavattanakul, M., and Lourith, N. (2016). Thailand Patent Filing No. 1601003321. Assigned to Mae Fah Luang University.
  4. Kanlayavattanakul, M., and Lourith, N. (2017). Ceylon spinach: a promising crop for skin hydrating products. Ind Crop Prod, 105, 24-28.
  5. Kanlayavattanakul, M., Fungpaisalpong, K., Pumcharoen, M., and Lourith, N. (2017). Preparation and efficacy assessment of malva nut polysaccharide for skin hydrating products. Ann Pharm Fr, 75, 436-445.
  6. Nualsri, C., Lourith, N., and Kanlayavattanakul, M. (2016). Development and clinical evaluation of green tea hair tonic for greasy scalp treatment. J Cosmet Sci, 67, 161-166.
  7. Meetham, P., Kanlayavattanakul, M., and Lourith, N. (2018) Development and clinical efficacy evaluation of anti-greasy green tea toner on facial skin. Rev Bras Farmacogn, 28(2), 214-217.
  8. Kanlayavattanakul, M., Rodchuea, C., and Lourith, N. (2012) Moisturizing effect of alcohol-based hand rub containing okra polysaccharide. Int J Cosmet Sci, 34, 280-283.

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Figure 1. Components and efficacy of green Ceylon spinach polysaccharide extract

Figure 1. Components and efficacy of green Ceylon spinach polysaccharide extract

The TPC for Ceylon spinach was 370 μg glucose/g, and the polysaccharide extract was 3.5-4.7% swelled in water, forming a thick, viscous solution (hydrogel).

Figure 2. Skin-hydrating efficacy of green Ceylon spinach polysaccharide extract

Figure 2. Skin-hydrating efficacy of green Ceylon spinach polysaccharide extract

A single application of the prepared green Ceylon spinach polysaccharide extract resulted in a better short-term skin hydration levels (7-28%) relative to the vehicle (water) and the control (untreated skin).

Figure 3. Skin-hydrating efficacy of green Ceylon spinach in a comparison with Malva nut5 and Okra8

Figure 3. Skin-hydrating efficacy of green Ceylon spinach in a comparison with Malva nut<sup>5</sup> and Okra<sup>8</sup>

The hydration efficacy of green Ceylon spinach polysaccharides proved to be superior over malva nut and okra polysaccharides,5, 8 previously assessed by a similar short-term efficacy evaluation.

Footnotes [CT1902 Lourith]

a Finn Chambers (8 mm), SmartPractice

b CM 825 Corneometer, Courage & Khazaka

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