Jojoba Oil Esters Ease Inflammation, Sensitivity and Water Loss from Skin and the Environment

Read this article and more in the September 2023 digital magazine

Recent climate change has triggered significant heat-related events including water shortages and even severe droughts throughout the world.^{1, 2} This has brought profound attention to, among other concerns, the need to focus carefully on the pragmatic use and careful management of precious water resources.

Simmondsia chinensis (jojoba) plant sprig, seed and natural golden oil

Consumers and scientists alike are concerned about water scarcity.^3-5 This is evident in cosmetic consumer literature that highlights the need to conserve water and reinforces the notion that waterless formulations are popular with consumers who understand that water sustainability is important.^6-8

Ideas for improving water scarcity include a renewed focus on areas where ingredient sustainability is impacting water use.^{9, 10} Simmondsia chinensis (jojoba) provides a good example. This unique plant grows around the world and is well-suited for semi-arid conditions.^11-13 Indeed, farms that grow jojoba plants are generally located in arid or semi-arid regions requiring outstanding water management to maintain the plants.

Furthermore, after jojoba seeds are harvested, their oil is typically extracted using mechanical cold-pressing techniques that extract the bulk of the oil. The resulting meal can then be used to help fertilize the plants, allowing for the cyclical agricultural use of the entire seed.

Jojoba oil also demonstrates well-documented skin mimetic characteristics and good tolerance by most skin types. This is important for today’s market and industry interest in topical ingredients that can help to mitigate and calm irritated and inflamed skin.¹⁴ Consumer reviews on retailer websites reveal that adverse skin reactions, excessive dryness potentially leading to irritation and redness are among the top complaints when trying a new product. These experiences could be alleviated by carefully selecting ingredients that provide benefits to address skin sensitivity.

Jojoba seed oil and its derivative esters are a staple ingredient, commonly used in cosmetics and personal care products.^{15, 16} In 2008, the Cosmetic Ingredient Review recognized jojoba oil and its esters and derivatives as safe for use in topical applications.¹⁷ The oil and esters are well-known to offer occlusive and hydrating benefits to skin and hair.¹⁸ Recent work also suggests jojoba oil may provide unique skin-penetration benefits when used in conjunction with actives such as retinol, thanks to the unique structure of jojoba oil.¹⁹

The oil is unique among the plant seed oils because it does not contain triglyceride fatty acid esters. Rather, it contains linear fatty acid esters that are waxes (for more on jojoba oil see Lionetti).^20-22 These waxes are liquid at room temperature, which gives the appearance of an oil.

Jojoba oil lends itself to interesting, natural chemical manipulations to provide unique trans-esterified esters (see Figure 1). The hydrogenation of its linear oils can produce naturally derived waxes that tend to melt at higher temperatures. While these hydrogenated esters require melting for formulation, they reform as soft to slightly hardened wax particles in w/o emulsions. It this respect, the esters can create solid wax dispersions rather than liquid droplets, improving spreadability upon topical application; although hardened waxes may also provide tactile benefits not seen with the liquid wax esters.

The waxes also share a strong similarity to the linear monoesters found in human skin sebum.²³ This gives the oil its skin compatibility and potential rapid absorption and occlusive benefits. These properties are less effective in the case of branched triglyceride oils.

While it is known that jojoba oil itself possesses anti-inflammatory benefits on skin, no apparent studies have examined this benefit from the trans-esterified jojoba esters.^{18, 20} As such, the present study examined the effects of commercially available jojoba esters^a in liquid, natural jojoba-like form in three skin studies measuring irritation mitigation, skin hydration and soothing properties, as described next.

Jojoba waxes share a strong similarity to the linear monoesters found in human skin sebum. This gives the oil its skin compatibility and potential rapid absorption and occlusive benefits."

Materials and Methods

Jojoba esters: The jojoba esters^a in this study were used as provided by the manufacturer.

Formulations: The formulas used to test effects on skin irritation and hydration are shown in Table 1. Formulations employed in the skin sensitivity study are shown in Table 2.

Skin TEWL and erythema protocols: The first study examined the use of the 2% jojoba esters to mitigate irritation induced by the application of a 2% dilute sodium lauryl sulfate solution applied under occlusion to the skin. This study was carried out in 30 volunteers (ages 20-64, Caucasian) who all signed informed consent prior to commencement of the study.

After 30 min in a climate-controlled (22°C, 55% RH) room, volunteers were marked at three sites on their backs. All three sites were occluded with patches^b moistened with 1 mL of 2.0% SLS solution. The occluded sites remained covered for 24 hr. After SLS treatments concluded, initial baseline measurements of trans-epidermal water loss (TEWL)^c and erythema^d were obtained. 

Two sites were then treated with either the placebo or active formulation (see Table 1). The third site remained untreated (control). Measurements of TEWL and erythema were again performed at 30 min and 1, 2, 4 and 8 hr after product treatment. The volunteers were then allowed to return home with instructions not to apply water to or wash their backs. The next day, volunteers returned to the lab and measurements were taken again at 24 hr for all parameters.

Inner volar forearm skin hydration protocol: The second study compared the skin hydration effects of the jojoba esters at 2% with a placebo and untreated skin on the inner volar forearms of volunteers. First, one week prior to the study, measurements of skin hydration were taken^e in 30 volunteers to establish a baseline hydration value. The volunteers then washed their inner volar forearms using an astringent bar soap. The skin was examined 7 days later to demonstrate the drying effects of the soap.

The test products (see Table 1) were then applied, leaving one site as the untreated control. Hydration measurements were made at 30 min and 1, 2, 4 and 8 hr after product treatment. Participants were sent home with instructions not to wash their inner volar forearms. They returned 24 hr later for a final hydration measurement.

Calculations: Results were compared to baseline and against each other using the student’s t-test. Confidence was established at 95% (p < 0.05).

Skin sensory study protocols: The third study tested the effects of the jojoba esters at 3% (or not, placebo) on skin sensory properties. Results were determined by panelists’ subjective responses to using the test formulations (see Table 2) on their inner volar forearms. Evaluations were carried out in 10 volunteers (ages 20-55) who signed informed consent.

One day before and the day of the study, participants cleaned their arms with an astringent liquid soap. They then applied a quarter-sized amount of each cream to their inner volar forearms with rubbing, during which participants were asked to rate their perception of the creams. Six parameters were assessed based on four possible responses (provided), where 1 = strongly disagree, 2 = disagree, 3 = agree and 4 = strongly agree:

• On a scale of 1-4, rate how you feel about the cushion of the two creams;
• On a scale of 1-4, rate how you feel about the formulation’s velvetiness on the skin;
• On a scale of 1-4, rate how you feel about each cream’s smoothness and softness on the skin;
• On a scale of 1-4, rate how you feel about each cream’s moisturizing effects on the skin;
• On a scale of 1-4, rate how you feel about how well each cream absorbs into the skin; and
• On a scale of 1-4, rate how you feel about texture of each cream on the skin.

The numerical results were tabulated and the average response for each question was plotted using a standard spider graph to compare the responses from the volunteers for each question for both the jojoba ester and placebo formulations.

Results and Discussion

TEWL: Results of the TEWL analyses are shown in Figure 2. The formulation containing 2% jojoba esters improved the TEWL of skin within 30 min of SLS irritation and barrier disruption. It also maintained its effectiveness for at least 2 hr versus the placebo and untreated controls. These effects are likely related more to the occlusive benefits of the jojoba esters.

Erythema: Data from the erythema tests is shown in Figure 3. Results demonstrated that 2% jojoba esters worked effectively to reduce erythema versus the untreated site. This effect was apparent early in the treatment regime, with effects lasting through 8 hr and 24 hr, versus the untreated and placebo treated sites.

Hydration: Results from the inner volar forearm skin hydration studies are shown in Figure 4. The corneometer showed that a single application of the formulation containing the jojoba esters imparted a rapid skin-hydrating effect, i.e., within 30 min of application, compared with the untreated and placebo sites. This benefit extended through the entire measurement period, demonstrating enhanced hydration even after 24 hr, compared with the untreated and placebo sites.

Sensory perception: Results from the sensory study in ten volunteers indicated the formulation containing 3% jojoba esters was preferred by panelists for every parameter rated (see Figure 5). As shown, the jojoba esters provided the formulation with a more luxurious feeling on the skin, compared with the placebo.

It is likely that, in the studies examined here, the jojoba esters are offering benefits through both their ability to reduce inflammation, which has previously been noted for jojoba oil, and their potentially occlusive effect, improving the skin barrier."

Discussion and Conclusion

Naturally manipulating the chemistry of jojoba oil to make trans-esterified esters results in an ingredient that can improve TEWL, erythema and hydration while imparting rich sensory benefits to soothe sensitive skin, as shown here. The chemical structure of the jojoba wax bears strong similarity to the monoesters known to exist in human sebum and excreted by the sebaceous glands. In this respect, jojoba esters are highly compatible with human skin and can help to mimic the benefits of components of skin sebum; e.g., occlusion.

It is likely that, in the studies examined here, the jojoba esters are offering benefits through both their ability to reduce inflammation, which has previously been noted for jojoba oil, and their potentially occlusive effect, improving the skin barrier. Taken together, the jojoba esters^a described afford skin care formulators an ingredient with good skin compatibility to provide high tolerance for sensitive skin while also being derived from a natural and water-conscious source.

References

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^a Liponate Jojoba 20 (INCI: Jojoba Esters) is a product of Vantage Specialty Chemicals.

^b Finn Chamber, 8 mm, SmartPractice

^c Tewameter 300, Courage + Khazaka, CKlectronic GmbH

^d Mexameter MX 18, CKeletronics

^e Corneometer, CKelectronic GmbH