Development and validation of an RP-HPLC method for the analysis of anthraquinones in noni fruits and leaves

Noni fruits and leaves, which have been used traditionally for thousands of years to improve health, are increasingly attracting the interests of consumers and researchers. A selective and validated HPLC method for the analysis of anthraquinones in noni fruits and leaves has been developed and is reported for the first time. Four anthraquinones, 5,15-dimethylmorindol (5,15-DMM, 1), lucidin (2), and alizarin (3), and rubiadin (4) are examined. The limits of detection of 1–4 were in the range of 1.0 and 20.0 ng. Intra- and inter-day precisions of 1 were determined to be less than 5.3%. The accuracy, expressed as the percent recovery of 1 after spiking at three concentrations ranged from 83.0% to 93.3%. Further, the linear correlation coefficient was >0.999, within the range of concentration investigated. The 5,15-DMM content of noni fruit puree and noni leaf infusion are between 0.186 to 0.202 μg/mL (ppm), and 5.82 to 20.93 ng/mL (ppb), respectively. Lucidin, rubiadin and alizarin were not detected in any of the noni samples. The presence of only trace amounts in the noni fruits and leaves may help to eliminate safety concerns regarding anthraquinone contents.