Phytochemical analysis and antibacterial activity towards methicillin-resistant Staphylococcus aureus of leaf extracts from Argania spinosa (L.) Skeels

Argania spinosa (L.) Skeels is an endemic Moroccan species belonging to Sapotaceae family. In this work, lipophilic and aqueous extracts were obtained from leaves and subjected to a chemical profiling by MS and LC-MS/MS. Pentacyclic terpenoids were identified and quantified in the lipophilic fraction, while phenolic compounds (mainly belonging to flavonols and flavan-3-ols) were identified in the aqueous fraction. The antibacterial activities of fractions were evaluated in vitro against both reference Gram-positive and -negative bacterial strains and clinical isolates of methicillin-sensitive and methicillin-resistant Staphylococcus aureus (MSSA and MRSA); in addition, the compounds quantified as main components in each extract were assayed against reference strains. A relevant antibacterial activity was observed against reference MSSA and MRSA strains of S. aureus: for the lipophilic fraction, MIC50 values obtained were 177.8 and 170.6 μg/mL for the former and the latter, respectively, while for the aqueous fraction were 215.5 and 233.3 μg/mL. These inhibitory activities could be mainly ascribed to ursolic and oleanolic acids, among pentacyclic terpenoids, and to quercetin concerning phenolic compounds. A remarkable antibacterial activity was also observed against clinical isolates, thus argan leaves can be considered of interest in the chemotherapy of human infections.