Limonene, a food additive, and its active metabolite perillyl alcohol improve regeneration and attenuate neuropathic pain after peripheral nerve injury: Evidence for IL-1ß, TNF-α, GAP, NGF and ERK involvement.

BACKGROUND: Limonene (LIM) and its main metabolite perillyl alcohol (POH) are ingredients found in food with promising chemical entities due to their pharmacological profile. In this study, we hypothesized that LIM and POH are two molecules capable of accelerating the regenerative process and alleviating neuropathic pain. METHODS: Animals were treated daily (LIM, POH and saline) for 28 days and during this period evaluated for mechanical hyperalgesia, astrocyte participation by immunofluorescence for GFAP, and ELISA was used to quantify IL-1ß and TNF-α in the spinal cord. Western blot analysis of the following proteins was also performed: GFAP, GAP-43, NGF and ERK. For motor deficit analysis, tests were performed to assess hind paw muscle strength and footprints through gait (SFI). RESULTS: Both POH and LIM accelerated the regenerative process and improved motor deficits comparing to positive control; however, POH was more effective, particularly between the 2nd and 3rd week after the nerve injury, increasing GAP-43, NGF and the phosphorylated ERK immunocontent. Moreover, POH and LIM were able to reduce hyperalgesia and astrocytosis. CONCLUSIONS: Both substances, LIM and POH, improved the regeneration process and sensory and motor function recovery in the PNI model in mice by mitigating the inflammatory reactions and up-regulating the neurotrophic process.

GC-MS Profile and Enhancement of Antibiotic Activity by the Essential Oil of Ocotea odorífera and Safrole: Inhibition of Staphylococcus aureus Efflux Pumps.

Considering the evidence that essential oils, as well as safrole, could modulate bacterial growth in different resistant strains, this study aims to characterize the phytochemical profile and evaluate the antibacterial and antibiotic-modulating properties of the essential oil Ocotea odorífera (EOOO) and safrole against efflux pump (EP)-carrying strains. The EOOO was extracted by hydrodistillation, and the phytochemical analysis was performed by gas chromatography coupled to mass spectrometry (GC-MS). The antibacterial and antibiotic-modulating activities of the EOOO and safrole against resistant strains of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were analyzed through the broth microdilution method. The EP-inhibiting potential of safrole in association with ethidium bromide or antibiotics was evaluated using the S. aureus 1199B and K2068 strains, which carry genes encoding efflux proteins associated with antibiotic resistance to norfloxacin and ciprofloxacin, respectively. A reduction in the MIC of ethidium bromide or antibiotics was used as a parameter of EP inhibition. The phytochemical analysis identified 16 different compounds in the EOOO including safrole as the principal constituent. While the EOOO and safrole exerted clinically relevant antibacterial effects against S. aureus only, they potentiated the antibacterial activity of norfloxacin against all strains evaluated by our study. The ethidium bromide and antibiotic assays using the strains of S. aureus SA1119B and K2068, as well as molecular docking analysis, indicated that safrole inhibits the NorA and MepA efflux pumps in S. aureus. In conclusion, Ocotea odorifera and safrole presented promising antibacterial and antibiotic-enhancing properties, which should be explored in the development of drugs to combat antibacterial resistance, especially in strains bearing genes encoding efflux proteins.