2.10. In Vitro Determination of Sun Protection Factor (SPF)

SPF was determined according to an in vitro method [46], known for being practical and presenting a good correlation with in vivo methodologies. Thus, formulations were prepared using polawax^® cream as a cosmetic base and extracted samples from all months harvested of both species, separately, were incorporated at a concentration of 10%. For spectrophotometric analyses, liquid samples of each formulation were prepared at 0.2 mg/mL, using absolute ethanol as solvent. Subsequently, a scan was made between the wavelengths of 200–400 nm using a spectrophotometer UV-Vis, UV-2550 Shimadzu, with a 1 cm optical path length quartz cell, analyses was done in triplicate and absolute ethanol was also used as blank. SPF was calculated by Equation (2), and an assay was made in triplicate.

Equation (2) SPF formula.

where,

CF = 10 (correction factor)

EE(λ) = erythematogenic effect

I(λ) = Sun intensity

ABS(λ) = absorbance