Antimicrobial Activities of <i>Pistacia lentiscus</i> Essential Oils Nanoencapsulated into Hydroxypropyl-beta-cyclodextrins

Abstract

The rising risks of food microbial contamination and foodborne pathogens resistance have prompted an increasing interest in natural antimicrobials as promising alternatives to synthetic antimicrobials. Essential oils (EOs) obtained from natural sources have shown promising anticancer, antimicrobial, and antioxidant activities. EOs extracted from the resins of <i>Pistacia lentiscus</i> var. <i>Chia</i> are widely utilized for the treatment of skin inflammations, gastrointestinal disorders, respiratory infections, wound healing, and cancers. The therapeutic benefits of <i>P. lentiscus</i>essential oils (PO) are limited by their low solubility, poor bioavailability, and high volatility. Nanoencapsulation of PO can improve their physicochemical properties and consequently their therapeutic efficacy while overcoming their undesirable side effects. Hence, PO was extracted from the resins of <i>P. lentiscus</i>via hydrodistillation. Then, PO was encapsulated into (2-hydroxypropyl)-beta-cyclodextrin (HPβCD) via freeze-drying. The obtained inclusion complexes (PO-ICs) appeared as round vesicles (22.62 to 63.19 nm) forming several agglomerations (180 to 350 nm), as detected by UHR-TEM, with remarkable entrapment efficiency (89.59 ± 1.47%) and a PDI of 0.1475 ± 0.0005. Furthermore, the encapsulation and stability of PO-ICs were confirmed via FE-SEM, ¹H NMR, 2D HNMR (NOESY), FT-IR, UHR-TEM, and DSC. DSC revealed a higher thermal stability of the PO-ICs, reaching 351.0 °C. PO-ICs exerted substantial antibacterial activity against <i>Pseudomonas aeruginosa</i>, <i>Staphylococcus aureus</i>, and <i>Escherichia coli</i> as compared to free PO. PO-ICs showed significant enhancement in the antibacterial activity of the encapsulated PO against <i>S. aureus</i> with an MIC90 of 2.84 mg/mL and against <i>P. aeruginosa</i> with MIC90 of 3.62 mg/mL and MIC50 of 0.56 mg/mL. In addition, PO-ICs showed greater antimicrobial activity against <i>E. coli</i> by 6-fold with an MIC90 of 0.89 mg/mL, compared to free PO, which showed an MIC90 of 5.38 mg/mL. In conclusion, the encapsulation of PO into HPβCD enhanced its aqueous solubility, stability, and penetration ability, resulting in a significantly higher antibacterial activity.