A rapid and non‐invasive fluorescence method for quantifying coenzyme Q10 in blood and urine in clinical analysis

BACKGROUND: Coenzyme Q10 (CoQ10) supplementation can improve cognition in patients with Alzheimer's disease (AD) and AD transgenic model mice. To ameliorate the discomfort that patients with AD suffer after several blood extractions, a non‐invasive method for detecting urine CoQ10 levels needs to be established. METHODS: Here, we developed a new technique of fluorescence spectrophotometry with ethyl cyanoacetate (FS‐ECA), on the basis of the principle that the chemical derivative obtained from the interaction between CoQ10 and ECA was detected by a fluorescence detector at λ(ex/em) = 450/515 nm. As a standard reference method, the same batches of the clinical samples were analyzed by high‐performance liquid chromatography with an ultraviolet detector (HPLC‐UV) at 275 nm. RESULTS: The limits of detection (LOD) and limits of quantization (LOQ) (serum: 0.021 and 0.043 mg/L; urine: 0.012 and 0.025 mg/L) determined by the FS‐ECA method were similar to that obtained through HPLC‐UV (serum: 0.017 and 0.035 mg/L; urine: 0.012 and 0.025 mg/L). More importantly, this new FS‐ECA technique as well as the conventional HPLC‐UV method could detect a marked difference in urine CoQ10 levels between AD and controls. CONCLUSION: Our findings suggest that this non‐invasive method for quantifying urine CoQ10 potentially replaces HPLC to detect blood CoQ10.