Background and scope: 1,8-Cineole (C10H18O), more widely known as Eucalyptol, is a bicyclic epoxy monoterpene that has long been used as an herbal therapeutic to treat inflammatory diseases due to its expectorant, antimicrobial and anti-inflammatory properties. In its pure form, 1,8-Cineole is used as an Active Pharmaceutical Ingredient (API) in the treatment of inflammatory respiratory diseases and colds. Its effectiveness in the treatment of bronchitis and sinusitis is considered proven. Scientists recognize the antimicrobial, antiviral, and cytotoxic potentials of 1,8-cineole and it is well established that the substance spreads almost everywhere in the human body following oral administration. However, it hasn’t been clear how cineole works in the organism, i.e. whether the immune system is stimulated or modulated or whether the API impacts the site of inflammation directly. A study was unleashed to gain further insight and knowledge. In it, Stir Bar Sorptive Extraction (SBSE) using the GERSTEL twister as well as the Thermal Desorption Unit (TDU 2) and Cooled Injection System (CIS 4, all from GERSTEL), was combined with GC-MS analysis to learn more about the distribution of the API in the body.
The study title: “Determination of orally administered 1,8-cineole in nasal polyp tissue from patients with chronic rhinosinusitis using gas chromatography and mass spectrometry”. The Schleswig-Holstein University Hospital, the Kloster-frau Healthcare Group and the Fraunhofer Institute for Molecular Biology and Applied Ecology (IME) in Schmallenberg, North Rhine-Westphalia, all based in Germany, were involved.
The main task: Determine 1,8-cineole in the target impact area, i.e. a homogenate of surgically removed inflammatory nasal polyp tissue.
Samples taken: Following the operation, tissue homogenates of removed nasal polyps were prepared in glass vials in ice-cold phosphate-buffered saline solution and submitted for analysis at dry-ice-cold -80 °C. The samples were thawed at 4 °C, brought to room temperature, homogenized, and an aliquot taken and brought to a total volume of 4 mL with distilled water.
Extraction: Extraction of 1,8-cineole and 1,4-cineole (internal standard) was performed using Stir Bar Sorptive Extraction (SBSE) with a PDMS Twister (GERSTEL Twister®).
Sample introduction to GC-MS: Transfer of the Twister to the TDU 2 was performed by a MultiPurpose Sampler (MPS robotic). Thermal desorption of the analyte and internal standard was performed in the GERSTEL TDU 2, the desorbed compounds were subsequently cryofocused in the CIS 4. A temperature program was finally used to transfer the compounds from the CIS 4 to the GC column for separation and Mass Spectroscopy (MS) determination.
Analysis: A GC-MS system from Agilent® Technologies (GC 6890N-5973 MSD) was used with Helium carrier gas and electron impact (EI) ionization at 70 eV at a source temperature of 230 °C. Selective ion monitoring (SIM) was performed focusing on the mass signals m/z 154 as quantifier and m/z 108 as qualifier for 1,8-cineole as well as m/z 111 and m/z 154 as quantifier and qualifier respectively for 1,4-cineole. The MS quadrupole temperature was set to 150 °C, the solvent delay to 4 minutes, and the acquisition time to 10 minutes.
Analysis results: The method was validated for selectivity, recovery, and reproducibility. The limit of quantification (LOQ) was determined to be 0.1 ng per sample extracted from cell lysate, regardless of sample volume or sample mass with a limit of detection (LOD) of 0.05 ng/sample. Calibration was performed over a concentration range of 0.05 to 5 ng/sample. Recovery was determined by MacKenzie et al. by analyzing six individual samples. The recovery mean was 102 % with a relative standard deviation of 2.7 %. Three blank samples (water) and three samples (cell lysate) were analyzed to ensure the specificity of the method. None of the blank samples had a concentration above the LOD. Additional matrix-containing samples were spiked with 0.1 ng, 1.0 ng, and 4.0 ng per sample, respectively, performed in triplicate. Average recovery rates were 121 % with a relative standard deviation (RSD) of 9.09 %, 107 % with an RSD of 4.12 % and 98.7 % with an RSD of 0.181 % respectively for the three levels.
Interpretation: To prove that orally administered 1,8-cineole reaches the nasal inner tissue, polyps from 30 chronic rhinosinusitis with nasal polyps (CRSwNP) patients were surgically removed and analyzed by SBSE-TD-GC-MS. Of the 30 patients, 15 had been administered cineole preparations over a period of 14 days leading up to the operation. 1,8-cineole was clearly detectable in tissue samples from nasal polyps, independent of individual body weight or BMI values of the patients. Oral administration of drugs containing 1,8-cineole resulted in significantly increased 1,8-cineole concentrations (above the LOQ) in the nasal polyps in eleven of 15 samples. Individual deviations could be explained by other factors. As such, the results indicate that there is a basis for a localized therapeutic effect.
Surprise: In samples from three members of the control group, 1,8-cineole was also found at levels above the LOQ. Subsequent interviews with control group members led the researchers to conclude that increased 1,8-cineole values were most probably due to ingestion of monoterpene containing herbs in the form of tea infusions or resulting from inhalations, leading to accumulation in the nasal tissue.
Conclusion: While a mild cold can heal quickly by itself, ingesting sage or peppermint teas containing 1,8-cineole is known as a helpful home remedy in the case of more serious conditions such as CRSwNP. The treatment of this disease can involve high dosage 1,8-cineole preparations as part of a phytotherapy described by a medical doctor. Their study, write MacKenzie et al., expands the understanding of the systemic impact of 1,8-cineole when used in therapy and thus its potential benefit for patients. Individual differences in the concentrations determined should be investigated further as related to metabolic differences.
Referenz
MacKenzie et al. (2023), Determination of orally administered 1,8‑Cineol in nasal polyp tissues from chronic rhinosinusitis patients using gas chromatography-mass spectrometry, Scientific Reports 13:3605, https://doi.org/10.1038/s41598-023-29941-x