Phytochemical content, in vitro antioxidants and antimicrobial activities of Daphne gnidium L. leaves

Abstract

Daphne gnidium is an endemic plant of Mediterranean basin, widely used for hair care and dermatological diseases in this area. This investigation aims to evaluate the phytochemical composition of D. gnidum leaves extracted by ultrasounds assisted extraction using aqueous and organic solvents (methanol, ethanol, chloroform and ethyl acetate) and to determine their antioxidant and antimicrobial activities. The ethanolic extract showed a higher concentration of total phenolic content (93.24 ± 0.07 mg GAE/g of dry extract), while the chloroform extract had a higher flavonoid content (60.94 ± 0.18 mg QE/g of dry extract) and condensed tannins (91.52 ± 2.23 mg CE/g of dry extract). Antioxidant potential was assessed by three methods (DPPH, ABTS and FRAP). Aqueous extract showed stronger antioxidant potential in DPPH test (IC₅₀ = 37.99 ± 1.51 µg/mL). Methanolic extract was the most potent in ABTS assay (IC₅₀ = 190 ± 4.86 µg/mL), while aqueous extract performed best in FRAP method (9.1 ± 0.08 mg AAE/g). The Pearson correlation test revealed a strong positive correlation between total flavonoid content, condensed tannins and antioxidant activity (DPPH, ABTS and FRAP assay), while a negative correlation was demonstrated between the DPPH, ABTS methods and total phenolic content. The antimicrobial activity was examined against four strains (Staphylococcus aureus, Bacillus subtilis, Proteus mirabilis and Candida albicans). At a concentration of 50 mg/mL, all tested extracts (aqueous, methanolic, ethanolic, chloroform and ethyl acetate) exhibited inhibitory effect against the four strains with inhibition diameters ranging from 8.67 ± 0.47 to 19.33 ± 0.94 mm, the latter achieved by the ethanolic extract against Proteus mirabilis. In conclusion, D. gnidium contains compounds with potential antioxidants and antimicrobial activities against certain harmful bacteria.