Caffeine and guarana are safe foods according to the American (FDA) and Brazilian (ANVISA) health agencies. However, data regarding the composition, quality, and safety of guarana-based food supplements sold in Brazil are limited. Most of the methods used for quantification of caffeine and other guarana chemical markers are based on complex extraction techniques as well as on gradient elution and do not evaluate the matrix effect nor the uncertainty estimation measurement. A simple and selective method for caffeine detection has been developed and validated using HPLC-UV. It shows linearity between 1 and 10 µg mL-1, has a significant matrix effect (p < 0.05) and its expanded uncertainty varies from 6.9 to 16.7%. Other parameters (selectivity, recovery, precision, robustness, limits of detection, and quantification) were satisfactory. The present study has analyzed 30 commercial samples of guarana-based food supplements (powders and capsules). Powder samples have shown an average caffeine level of 25.27 ± 5.20 mg g-1 while capsules 28.53 ± 13.81 mg g-1. No significant difference between the two types of samples has been observed (p > 0.005).
Keywords:
bioactive substances; food supplements; high performance liquid chromatography; methylxanthines; quality control
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