Antimycobacterial, antioxidant and cytotoxic activities of essential oil of gall of Pistacia atlantica Desf. From Algeria

The essential oils (EOs) of unripe galls (from male and female plants) of a total number of 52 samples of Pistacia atlantica collected from different regions in Algeria were analysed by GC/MS and GC. The yields of the extraction of the EO by hydrodistillation vary from low to high values (0.08–1.89% v/w). The results of both methods of principal component analysis and hierarchical ascendant classification revealed the presence of two different chemotypes: α-pinene chemotype and α-pinene/sabinene/terpinen-4-ol chemotype.

Medicinal plants are rich sources of bioactive compounds with diverse pharmacological properties, including antimicrobial activities. This study aimed to assess the antibiofilm potential of methanol and ethanol extracts from nine selected medicinal plants, as well as their synergistic effects with doxycycline against Bacillus strains. Standard procedures were employed to determine the phytochemical composition, total phenolic, and flavonoid contents of the extracts. The antibacterial activity was evaluated using the broth microdilution method, while biofilm formation was assessed via the microtiter plate method. Antibiofilm activity was determined using the 3‐(4,5‐dimethyl‐2‐thiazolyl)‐2,5‐diphenyl‐2H‐tetrazolium‐bromide (MTT) assay. Combination studies were conducted using the checkerboard microdilution method. All extracts contained phenols, flavonoids, steroids, triterpenes, and anthraquinones. The methanolic extract of Psidium guajava exhibited the highest total phenolic and flavonoid contents (90.48 ± 0.55 mg GAE/g), while the ethanolic extract of Olax subscorpioidea showed the highest flavonoid content (6.48 ± 0.33 mg QE/g). Ethanol extracts of Eucalyptus globulus and Psidium guajava and methanolic extract of Syzygium jambos demonstrated significant antibacterial activity against Bacillus anthracis 34F2 Sterne strains, with a MIC value of 64 μg/mL. Biofilm formation in Bacillus strains was notably enhanced in the presence of glucose. The methanolic extract of O. subscorpioides exhibited the highest biofilm imbibition (85%), while Picralima nitida methanolic extract showed the most effective biofilm eradication (79%). The combination of Solanum torvum ethanol extract with doxycycline displayed synergistic effects against biofilm formation inhibition and eradication in all tested Bacillus strains. Taken together, Solanum torvum ethanol extract shows promise for developing new combination antibacterial therapies.

L’activité antimicrobienne des huiles essentielles de galles de Pistacia atlantica récoltées dans trois régions (Aïn-Oussara, Laghouat et Kheneg) a été évaluée sur sept souches pathogènes (Escherichia coli, Bacillus cereus, Pseudomonas aeruginosa, Staphylococcus aureus, MRSA+, Salmonella typhi et Candida albicans), en utilisant les méthodes de diffusion sur gélose, de microdilution et celle de microatmosphère (seulement pour Candida albicans). Les huiles essentielles ont révélé un effet antimicrobien remarquable contre les micro-organismes testés, avec des valeurs de CMI et de CMB variant de 0,13 à 7,99 μl/ml et de 0,25 à 7,99 μl/ml, respectivement. Une activité importante a été observée pour les échantillons de la station Kheneg contre l’espèce Candida albicans avec une zone d’inhibition de 68 mm (50 μl). Ces résultats suggèrent que les huiles essentielles testées pour leur activité antimicrobienne peuvent être classées comme bactéricides.