## 3 Results
### Long-Term Stability Analysis of the Selected Formulation for Volunteer Testing
The skin elasticity tests (R2 and R5 parameters) showed that the cream with micellar extract of common bean (_P. vulgaris_) sprouts statistically significantly improved total elasticity (R2) after 8 weeks by (+8.89%) and after 12 weeks by 13.30%. In the placebo group, a statistically significant increase was observed after 8 weeks (+7.61%) and 12 weeks (+8.50%). In the CR group, a statistically significant increase was observed only after 12 weeks (+6.38%). Statistically significant differences between the placebo and extract groups were observed after 12 weeks. The effect of the cream with extract and the reference cream on the improvement of the R5 parameter was statistically significant only after 12 weeks of use, while no improvement in the R5 parameter was observed in the case of the placebo cream. Statistically significant differences in the improvement of the R5 parameter were noted between the placebo cream and the cream with the extract only after 8 weeks of use. In the remaining cases, no statistically significant differences were noted. Figure 3: Characteristics of the Placebo group, Extract group, and CR—reference group in measure 1—M1, measure 2—M2, measure 3—M3, and measure 4—M4 for the Sebum Parameter. Skin type is a complex parameter primarily determined by pigments such as hemoglobin, melanin, bilirubin, and caroten. The levels of these pigments can change in response to UV radiation and certain substances, including medications. When analyzing skin color, two key indices are evaluated: the Erythema Index (EI) and the Melanin Index (MI). Erythema, represented by EI, refers to localized skin redness caused by the dilation of superficial blood vessels. MI, on the other hand, reflects the amount of melanin, a natural pigment found in living organisms [34]. The Sebumeter(r) SM 815 cassette directly measures skin oiliness. The instrument operates based on the principle of spot photometry. The cassette features a matte film with specific opalescence properties. When covered with a lipid layer, the film becomes transparent under light. The measurement, expressed in \(\upmu\)g sebum/cm\({}^{2}\), reflects the difference in transparency of the tape before and after skin contact. The measurement result is the difference in the transparency of the tape before and after contact with the skin, expressed in the range of 0-350 \(\upmu\)g of sebum/cm\({}^{2}\)[31; 32]. Sebum levels were measured at three different locations on the forehead and the result is presented as the average of these measurements. Statistical analyses for the Melanin Index (MI) and Erythema Index (EI) and for the Sebum Parameter were performed using, for within-group comparisons, repeated-measures [PERSON]'s test and between-group differences were analyzed using the Kruskal-Wallis test with post hoc Mann-Whitney U tests used where applicable. A \(p\)-value of \(<\)0.05 was considered statistically significant. The measurement of the Melanin Index demonstrated a slight lightening effect over time within the tested groups. For both the cream with the extract and the reference cream, the skin lightening effect was (\(-\)7.3%) for the cream with the extract, which was statistically significant, and (\(-\)6.4%) for the reference cream, which was not statistically significant. Comparing the skin lightening effect between the groups, no statistically significant changes were observed. Regarding the reduction in skin redness (Erythema Index), a decrease in redness was noted at (\(-\)3.68%), (\(-\)12.1%), and (\(-\)10.36%) for the placebo cream, the cream with the extract, and the reference cream, respectively. However, these values were not statistically significant. No statistically significant changes were observed when comparing the effect of the creams on redness levels between the groups at any stage of the study. The analysis of sebum secretion on the skin's surface did not show any statistically significant effect of the tested formulations on this parameter at any stage of the study.