p. 9-11 / SUN CARE
Vegetable oils as bioactive adjuvants for sunscreens
CAMILA AREIAS DE OLIVEIRA*, DEBORAH DE OLIVEIRA NISHIKAWA, TATIANA SANTANA BALOGH, PAULA SOUZA PRESTES, VLADI OLGA CONSIGLIERI, TELMA MARY KANEKO, MARIA VALÉRIA ROBLES VELASCO, ANDRÉ ROLIM BABY
School of Pharmaceutical Sciences of University of São Paulo, Laboratory of Cosmetology, Dept. of Pharmacy
580 Prof. Lineu Prestes Av., Bl. 13/15, Conjunto das Químicas, Cidade Universitária, 05508-900, São Paulo, SP, Brazil
KEYWORDS: Bioctive sunscreens: Ethylhexyl methoxycinnamate; Simmondsia chinensis; Cymbidium grandiflorum; Daucus carota L.; Lycopersocon esculentum.
ABSTRACT: Nowadays, it is observed the use of naturally occurring plant products for the prevention of UV-induced skin photodamage and for the improvement of Sun Protection Factor (SPF). This research proposed the development and in vitro efficacy evaluation of bioactive sunscreens containing vegetable oils associated or not to an UVB filter. Formulations were developed with an anionic self-emulsifying agent. Ethylhexyl methoxycinnamate (EHM) was selected as UVB filter and the next vegetable oils were individually associated or not to the EHM: Simmondsia chinensis (jojoba), Cymbidium grandiflorum (orchid), Daucus carota L. (carrot) and Lycopersicon esculentum (tomato). The following determinations were performed (base; base + EHM; base + oils; and base + EHM + oils): pH value, apparent viscosity (cP) and in vitro SPF by reflectance spectrophotometry with integrated sphere (RSIS) (Labsphere® UV- 2000S). One-way ANOVA followed by Tukey test (p<0.05) was the statistical treatment. The pH values of pHmeter ranged from 6.3 to 6.9. It was verified that L. esculentum oil promoted the apparent viscosity lowest value (15,600 cp). In vitro efficacy indicated the elevation of SPF from 4.25 ± 0.5 (base + EHM) to 7.25 ± 1.5 (base + EHM + D. carota L. and base + EHM + L. esculentum). A synergism on the SPF increase was statistically identified when 10 percent w/w D. carota L. (carrot) oil or 10 percent w/w L. esculentum (tomato) oil was individually associated with 7.5 percent w/w EHM. These results indicated that there was a synergism between these oils rich in carotenoid pigments and the employed UVB filter. The RSIS was suitable for the estimation of in vitro efficacy through SPF determination of the above bioactive sunscreens.
The solar spectrum is composed by ultraviolet (100-400 nm), visible (400-800 nm) and infrared (>800 nm) radiation. The ultraviolet (UV) radiation is conveniently divided into UVC (200-290 nm), UVB (290-320 nm) and UVA (340-400 nm). The UVA radiation itself is subdivided in UVA1 (340-400 nm) and UVA2 (320-340 nm) (1-3).
The over exposure of human skin to UV radiation may cause sunburn, erythema (mostly caused by exposure to UVB radiation), photoaging and may increase the risk of melanoma and non-melanoma skin cancer (4-7).
Sunscreens are mainly utilized for the prevention of the erythema formation decurrent from sun exposure. These formulations reduce the incidence of ultraviolet radiation on the skin’s surface, thus assisting to prevent its deleterious effects (2, 4, 8).
Currently there is a tendency to developing broad spectrum sunscreen formulations with reduced amounts of chemical UV filters. Bioactive and natural substances have therefore been widely investigated as whether they are capable of protecting the skin against UV radiation or of increasing the protection supplied by filters (2, 7).
Botanical constituents may present different proprieties such as antioxidant and photoprotective activities. These two proprieties justified the use of natural compounds in sunscreens. The scientific literature relates that some botanical ingredients are able to prevent the UV-induced skin photodamages and to improve the Sun Protection Factor (SPF) of the sunscreens (2).
Based on that the present work aims to investigate, developing and evaluating the in vitro efficacy (SPF value) of bioactive sunscreens containing vegetable oils (Simmondsia chinensis, Cymbidium grandiflorum, Daucus carota L. and Lycopersicon esculentum) associated or not to an UVB filter (ethylhexyl methoxycinnamate (7).
The SPF value concerns mainly the effects of the UVB radiation on the skin. It is the universal indicator for the description of the sunscreen’s efficacy against sunburn (1, 7).
In vitro methods for SPF estimation have been introduced based on the assumption that the protection against UV radiation provided by sunscreens is dependent on their absorption characteristics and concentrations (8, 10).
MATERIALS AND METHODS
Ten formulations were developed using an anionic self-emulsifying base. Ethylhexyl methoxycinnamate (EHM) was selected as UVB filter and the following vegetable oils were individually associated or not to the EHM: Simmondsia chinensis (jojoba), Cymbidium grandiflorum (orchid), Daucus carota L. (carrot) and Lycopersicon esculentum (tomato).All oils used were obtained commercially.
The formulations’ qualitative and quantitative compositions are described on Table 1 below.
Preparation of the formulations
The components of the oil phase were all mixed together as well as the components of the water phase. Afterwards, the water phase was poured onto the oil phase under agitation.
When the mixture was homogeneous, the preservant and the silicone were added and the formulation was again homogenized.
pH and apparent viscosity determination
All ten formulations had their pH and apparent viscosity measured in replicates of four. The pH values were determined by pHmeter®.The apparent viscosity values (cP) were attained by Brookfield® viscosimeter using TR11 spindle and 30 rotations per minute.
In vitro photoprotection assessment
The photoprotective efficacy assessment was performed in vitro by quantifying the Sun Protection Factor (SPF) value of the prepared formulations, which was measured by reflectance spectrophotometry with integrated sphere (RSIS) (Labsphere® UV-2000S Ultraviolet Transmittance Analyzer).
Statistical analysis were performed with the software STATISTICA® Release 7.0. Data were statistically treated using one-way ANOVA followed by Tukey test (p<0.05).
The samples were accurately weighted and uniformly applied with a glove-coated finger on the rough side of PMMA (poly methyl methacrylate) plates in the ratio of 0.75 mg/cm2. The samples were then allowed to dry at room temperature during 20 minutes protected from the light (2, 10).
The plates were prepared in replicates of four, and nine different points per plate were measured for each sample.
RESULTS AND DISCUSSION
The average pH, apparent viscosity and in vitro SPF results obtained for all formulations are summarized in Table 2 below as well as the results of the statistical analysis.
None of the formulations presented statistically different pH values.
As shown in Table 2, formulations with the L. esculentum oil associated or not with the EHM lowered the apparent viscosity value (15600 cP and 17950 cP).
Formulations F7, containing 7.5 percent EHM and 10 percent C. grandiflorum oil (SPF 5.25 ± 1.5) and F10, containing 7.5 percent EHM and 10 percent S. chinensis oil (SPF 6.25 ± 0.9) did not present a statistically significant difference when compared to formulation F6.
The in vitro photoprotective efficacy assessment demonstrated that the formulations F8, with 7.5 percent EHM and 10 percent L. esculentum oil (SPF 7.0 ± 1.4), and F9, with 7.5 percent EHM and 10 percent D. carota L. oil (SPF 7.25 ± 1.5), presented a statistically significant increase in the SPF values when compared with formulation F6, containing only the EHM filter and no vegetal oil (SPF 4.25 ± 1.7).
These results indicate that there was a synergism between these oils rich in carotenoid pigments (Daucus carota L. and Lycopersicon esculentum) and the employed UVB filter. Carotenoid pigments protect the photosynthetic apparatus in plants by dissipating excess energy, and several lines of evidence support the idea that carotenoids also protect human skin against UV-induced lesions. Tomatoes and tomato products are major sources of lycopene. Following ingestion of dietary products rich in lycopene, photoprotective effects have been demonstrated (7).
Results indicated that the combination of vegetable oils with the UVB filter did not show significant variations in pH and viscosity values. The in vitro photoprotective efficacy assessment demonstrated that there was a synergism between the formulations with the combination of oils rich in carotenoid pigments (Daucus carota L. and Lycopersicon esculentum ) and EMH. The RSIS was suitable for the estimation of the in vitro photoprotective efficacy involving the SPF determination of the developed bioactive sunscreens.
FAPESP (2008/57800-0), CAPES, Chemyunion.
Table 1. Qualitative and quantitative (% w/w) composition of the formulations.
Table 2. pH, apparent viscosity and in vitro SPF results of the developed formulations.
Legend: X = presence; / = absence
Legend: SD = Standard Deviation; CV = Coefficient of Variation
Different letters indicate statistically significant differences between samples of each column (p<0.05; n=4).
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