Vegetable oils as bioactive adjuvants for sunscreens
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).