Medicago spp. extracts as promising ingredients for skin care products

Agro-industrial by-products have the potential to be used with different purposes thus providing economical advantage to otherwise disposable residues. In particular, the field of skin care products and cosmetics may benefit from these remaining materials. Hydro-alcoholic extracts of seven species of Medicago (M. minima, M. tornata, M. truncatula, M. rigidula, M. scutelata, M. segitalis and M. sativa) were screened for antioxidant, cytotoxicity and antimicrobial activities aiming at their application as functional ingredient in skin formulations. Antioxidant activity was evaluated by standard methods such as DPPH· and FRAP. In both methods the antioxidant activity of M. segitalis displayed the highest antioxidant activity (214.49 ± 6.69 μmol Trolox equivalent per g db for DPPH; 120.84 ± 1.86 μmol/mg db for FRAP). For DPPH M. rigidula showed the lowest antioxidant activity (127.18 ± 1.96 μmol Trolox equivalent per g db) and for FRAP M. minima showed the lowest one (58.05 ± 6.09 μmol per mg db). Also, the total phenolic and total flavonoid contents (TPC and TFC, respectively) were evaluated. The TPC of the different extracts varied from 21.96 mg to 36.41 mg GAE/g db sample, being the highest TPC obtained for M. minima and the lowest for the M. scutelata. TFC varied from 5.54 to 11.67 mg CEQ/g db sample. Linear negative correlations were established between the total phenol contents and for both the antioxidant activity methods. The extracts were also screened for cytotoxicity using MTS and LDH assays in two different skin cell lines (HaCaT and HFF-1) and showed low cytotoxicity. Preliminary assays for antimicrobial potential showed that extracts from Medicago display antibacterial activity, with MIC values of 31.3 μg/mL and 125 μg/mL for some Gram-positive and Gram-negative bacteria, respectively. Taken together, the results suggested that Medicago hydro-alcoholic extracts are a potential source of natural compounds with high levels of antioxidant activity, low cytotoxicity for skin cells and the ability to potentially prevent microbial infections of the skin due to its antimicrobial effect, as well as contribute as a natural preservative in cosmetic products. All referred above justify their possible uses in skin care products.