METHOD DEVELOPMENT FOR THE DETERMINATION OF NAPTHODIANTHRONES AND PHLOROGLUCINOLS IN ST. JOHN’S WORT
Rachel A. Lieberman and Lane C. Sander
St. John’s wort (SJW, Hypericum perforatum L.) has been used as a traditional medicine in the treatment of abdominal pain, wound healing and burns, to name a few, and more recently as an antidepressant. The unique marker compounds of SJW include naphthodianthrones (hypericin and pseudohypericin) and phloroglucinols (hyperforin and adhyperforin). The levels of these phytochemical components may vary in floral, leaf, and stem tissue. The National Institute of Standards and Technology (NIST) in collaboration with the National Institutes of Health Office of Dietary Supplements (NIH-ODS) and the Food and Drug Administration (FDA) is producing a suite of SJW Standard Reference Materials (SRMs) including a powdered leaf, methanolic extract, carbon dioxide extract, and finished product forms. These SRMs are intended to assist dietary supplement manufacturers in providing accurate values for their product labels.
At least two independent analytical methods are necessary for the certification of an SRM. The efficiency of Soxhlet extraction and ultrasonic extraction have been compared. SJW marker compounds are separated with a C18 column and detected by absorbance at 520 and 590 nm for the napthodianthrones and at 272 nm for the phloroglucinols. Preliminary concentrations of the marker compounds in the SRMs have been determined with an internal standard calibration approach. Further studies will include development of a second separation method, evaluation of analyte stability, and value assignment of the SRMs.