One gram of onion added to the food of rats inhibits significantly (p < 0.05) bone resorption as assessed by the urinary excretion of tritium released from bone of 9-week-old rats prelabeled with tritiated tetracycline from weeks 1 to 6. To isolate and identify the bone resorption inhibiting compound from onion, onion powder was extracted and the extract fractionated by column chromatography and medium-pressure liquid chromatography. A single active peak was finally obtained by semipreparative high-performance liquid chromatography. The biological activity of the various fractions was tested in vitro on the activity of osteoclasts to form resorption pits on a mineralized substrate. Medium, containing the various fractions or the pure compound, was added to osteoclasts of new-born rats settled on ivory slices. After 24 h of incubation, the tartrate-resistant acid phosphatase positive multinucleated cells, that is, osteoclasts, were counted. Subsequently, the number of resorption pits was determined. Activity was calculated as the ratio of resorption pits/osteoclasts and was compared to a negative control, that is, medium containing 10% fetal bovine serum only and to calcitonin (10(-12) M) as a positive control. Finally, a single peak inhibited osteoclast activity significantly (p < 0.05). The structure of this compound was elucidated with high-performance liquid chromatography-electrospray ionization-mass spectrometry, time-of-flight electrospray ionization mass spectrometry, and nuclear magnetic resonance spectroscopy. The single peak was identified as gamma-L-glutamyl-trans-S-1-propenyl-L-cysteine sulfoxide (GPCS). It has a molecular mass of 306 Da and inhibits dose-dependently the resorption activity of osteoclasts, the minimal effective dose being approximately 2 mM. As no other peak displayed inhibitory activity, it likely is responsible for the effect of onion on bone resorption.

Background: Due to variable absorption and extensive first-pass metabolism, the bioavailability of oral delta-9-tetra­hydrocannabinol (THC) and cannabidiol (CBD) is low, and, therefore, alternative application forms are necessary. Methods: In an open-label, 2-period phase-1 study on 11 healthy volunteers, a combination of THC and CBD was compared by pulmonary (inh) and intravenous (iv) application. The liquid aerosol was produced by an in vitro validated pressurized metered-dose inhaler (pMDI) device, releasing 41–44% of the cannabinoid dose, enabling a dosage of 81 µg THC and 87 µg CBD per actuation. Three subjects (pilot trial, low-dose session) received 324 and 348 μg THC and CBD, respectively, and 8 subjects (main trial, high-dose session) received 648 and 696 µg THC and CBD, respectively. The addition of the local anesthetic lidocaine to the inh preparation should prevent airways irritation and coughing. The pharmacokinetic evaluation was based on plasma profiles acquired by gas chromatography-mass spectrometry. Adverse effects were monitored by visual analog scales and measuring vital functions. Results: After low inh doses, THC and CBD were not measurable in plasma longer than 20 and 40 min after administration, respectively. Therefore, only plasma levels resulting after high doses were further evaluated. After inh and iv administration, THC plasma peaks were observed 5 min post-drug, with THC peak concentrations ranging from 3 to 22 and from 13 to 40 ng/mL, respectively. CBD peaks were also measured 5 min after inh and iv administration, with concentrations ranging from 2 to 17 and from 14 to 26 ng/mL, respectively. The elimination half-lives were 7 and 11 min after inh and 22 and 24 min after iv administration for THC and CBD, respectively. The mean inh bioavailability (calculated vs. iv) was 55 ± 37 and 59 ± 47% for THC and CBD, respectively. Conjugated 11-carboxy-THC was the main THC metabolite. The nebulized aerosol was generally well tolerated with little or no coughing and only slight psychological adverse effects. These were more distinct after iv administration, especially irritations and hallucinations. Besides moderate tachycardia, the vital functions stayed unchanged. Conclusions: We conclude that a THC-CBD inh aerosol shows favorable pharmacokinetic properties, which are similar to those of an iv preparation. Adding a local anesthetic is recommended to prevent coughing, which decreases absorption. The negligible psychoactivity may be due to an anti­psychotic effect of CBD, the low THC dosage, and/or the decreased formation of the psychoactive metabolite 11- hydroxy-THC. Therefore, the inhalation via a pMDI is a viable, safe, and well-tolerated alternative to the oral administration.

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