The molecular structure of β-alanine is resistant to sterilising doses of gamma radiation

Abstract

β-alanine is the rate-limiting point for the endogenous synthesis of carnosine in skeletal muscle. Carnosine has a wide range of implications for health, normal function and exercise performance. Whilst the physiological relevance of carnosine to different tissues remains enigmatic, β-alanine administration is a useful strategy to investigate the physiological roles of carnosine in humans. Intravenous administration of β-alanine is an interesting approach to study carnosine metabolism. However, sterilisation is mandatory due to the nature of the administration route. We evaluated whether sterilising doses of gamma radiation damages the molecular structure and leads to the loss of functional characteristics of β-alanine. Pure β-alanine was sterilised by gamma radiation in sealed glass vials using a 60Co multipurpose irradiator at a dose rate of 8.5 kGy.hour-1 totalising 10, 20, 25 30 and 40 kGy. The molecular integrity was assessed by X-ray Diffraction and changes in content were determined by High Performance Liquid Chromatography (UV-HPLC) and Triple Quadrupole Mass Spectrometer (HPLC/MS-MS). Sterility assurance was evaluated by inoculation assay. To examine whether functional properties were preserved, β-alanine was infused in one participant, who rated the level of paraesthesia on the skin using a 0-3 scale. Urinary β-alanine was quantified before and 24-h following β-alanine infusion using HPLC-ESI+-MS/MS. Irradiation resulted in no change in the crystal structure of β-alanine, no degradation, and no new peaks were identified in the dose range assayed. The inoculation assay showed the absence of viable microorganisms in all β-alanine samples, including those that did not undergo irradiation. Intravenous infusion of β-alanine resulted in paraesthesia and it detected in the urine as per normal. We conclude that gamma radiation is a suitable technique for the sterilisation of β-alanine. It does not lead to degradation, damage to the β-alanine structure, content or loss of function within the evaluated irradiation conditions.

Fig 1. Representative chromatograms of selected reaction monitoring (SRM) of β-alanine after gamma irradiation at dose rate of 8.5 kGy hour^-1 and absorbed doses ranging from 0 to 40 kGy.

Chromatograms were obtained in a blank control, a non-irradiated 50 mM control, and 10–40 kGy irradiated 50 mM β-alanine samples.

Fig 2

X-ray Diffractograms of β-alanine and β-alanine standard (27–1501—PDF-ICDD) before (a) and after gamma irradiation at dose rate of 8.5 kGy hour^-1 and absorbed doses ranging from 10 to 40 kGy (b).

Fig 3. β-alanine peak intensities and concentrations obtained in a midstream urine sample before intravenous infusion of β-alanine and in a 24-h urine sample obtained after β-alanine infusion (Fig 2A).

Symptoms of paraesthesia reported by the participant during intravenous infusion of irradiated β-alanine (Fig 2B).