14 and 15 The in vitro method measures the reduction

of the irradiation by measuring transmittance after passing through a film of product. As in the operative conditions of the transmission measurement are correct, this to be a very precise and single value, always reproducible for the same product and expressed as a single UV curve, in the percent transmittance or absorbance scale (Fig. 1). The crude R. kordesii petal extract, the gel formulation (1.5% carbomer 937) containing R. kordesii petal extract were analyzed for the in vitro SPF. The selleck chemicals llc crude R. kordesii petal extract gel formulation was dissolved in methanol UV solv:water (6:4). Scans of the samples in solution were run from 320 to 290 nm using 1 cm quartz cuvettes in a Shimadzu UV-1700 spectrophotometer. 16 The commercial sunscreens, Himalaya® SPF 30, were used for the calculation of the correction factor and a solution of 8% homosalate (v/v) diluted to 0.2 μg/ml was used as standard. The SPF model used in this study was based on the following equation proposed by Mansur et al. 17 equation(1) SPF=CF×∑290320EE(λ)×I(λ)×abs(λ)where CF is correction factor, determined by sunscreens with known SPF, so that a solution containing 8% of

homosalate gives SPF = 8; EE(λ) the erythemal efficiency spectrum; I(λ) the solar simulator spectrum as measured with a calibrated spectroradiometer; equation(2) ∑290320EE(λ)×I(λ)=290–320nmwhere, KRX-0401 manufacturer GPX6 290–320 nm in 5 nm

increments; abs(λ) is the spectroradiometer measure of sunscreen product absorbance. Table 3 shows the normalized values of the product function used in these studies and were calculated by Sayre et al. 17 and 18 The data were analyzed statistically by factorial analysis of variance (ANOVA). The Tukey–Kramer test was then used to determine significant differences between groups. The chemical stability of the R. kordesii root extract gel was determined according to the concentration of R. kordesii extracts at different storage temperatures (5, 25 and 45 °C) for 3–4 months. The final concentration was expressed as micrograms of R. kordesii extracts per gram of gel formulation. Carbomer frequently interacts with cationic drugs and excipients due to its numerous carboxylic acid groups. 19 In vitro studies using carbomers 973 showed that its interaction with substances commonly used in the pharmaceutical industry, such as lidocaine and mebeverine hydrochloride, was a function of pH, drug, polymer concentration and electrolytes. 20 All samples stored at 5 and 25 °C were stable over the time of experiment (3–4 months). All of them showed an initial decrease (20%) between days 0 and 1 and then remain constant over time. The samples stored at 45 °C were stable up 7 days then the degradation of gel structure was observed after 7 days. The correction factor was calculated for commercial sunscreen (Himalaya® SPF 30) using Eq.