Antioxidant and antimicrobial activities of Lavandula dentata extracts: A comparative study of solvent efficacy

Lavandula dentata, commonly known as “el khouzama” in Algeria, is a medicinal plant widely recognized for its aromatic and therapeutic properties. In the context of increasing bacterial resistance to antibiotics and the harmful effects of oxidative stress, the flowers and leaves of L. dentata may offer a promising natural alternative. This work aims to evaluate the antioxidant and antimicrobial effects of ethanolic and aqueous extracts obtained from the aerial parts of L. dentata. Both extracts significantly inhibited DPPH free radicals, with the ethanolic extract showing greater efficiency (IC₅₀ = 0.53 ± 0.06 mg/mL). The aqueous extract reduced ferric iron to ferrous iron to a significantly higher extent (99.21 ± 0.06 mM Fe²⁺/g extract) compared with the ethanolic extract (69.22 ± 0.13 mM Fe²⁺/g extract) (p < 0.05). The ethanolic extract exhibited a total antioxidant capacity of approximately 19.15 ± 0.01 mg Eq AA/g DM, which was higher than that of the aqueous extract (8.64 ± 0.02 mg Eq AA/g DM) (p > 0.05). The evaluation of antimicrobial activity using the agar diffusion method and MIC determination revealed that all seven microbial strains were highly sensitive to the ethanolic extract, which produced inhibition zones ranging from 13 ± 0 to 17 ± 2.45 mm (p < 0.01). The minimum inhibitory concentration (MIC) was 40 ± 0 mg/mL for all strains. The aqueous extract was effective only against E. hirae and C. albicans, producing inhibition zones of 14.67 ± 0.47 mm and 11.33 ± 1.00 mm, respectively, with MIC values of 7.5 ± 4.33 and 8.33 ± 2.89 mg/mL (p > 0.05). Overall, L. dentata demonstrates potent antioxidant and antimicrobial properties, supporting its potential application in the agri-food and pharmaceutical industries.