Application of Protein Phosphatase 1 Inhibition Assay and Reversed Phase Liquid Chromatography for the Detection of Microcystins in Algal Dietary Supplements
YI-MIN CHEN1,2, RANG HUANG2 AND HONG-NONG CHOU1*
1. Institute of Fisheries Science, National Taiwan University, 1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan, R.O.C.
2. Institute of Oceanography, National Taiwan University, Taipei 10617, Taiwan, R.O.C.
(Received: August 6, 2004; Accepted: November 25, 2004)
ABSTRACT
Protein phosphatase 1 inhibition assay and reversed phase high performance liquid chromatography were adjusted for the detection of microcystins in Chlorella and Spirulina dietary supplements. Various sample preparation procedures for the enzyme and chemical assays were tested by the toxin-spiked samples to improve the sensitivity and accuracy of these methods. A silica gel solid phase extraction coupled with a deactivated elution had remarkably reduced the matrix interference from sample extracts and improved the detection of microcystins in both assays. High performance liquid chromatography could give the composition of different microcystins in the sample if the resolution of separation and toxin standards were available. On the contrary, protein phosphatase 1 inhibition assay gave an accumulated inhibition activity of the sample that could be converted to MCYST-LR equivalent according to the IC50 of this standard. A good sensitivity of 50 ppb of microcystin in dried algal samples, was reached using the methods established in this research. Both enzyme and chemical assays were applied for the detection of possible microcystin contamination in the commercial
products of algal dietary supplement. It was found that all nine samples of algal product examined in this study were free from microcystins.
Key words: solid-phase extraction (SPE), microcystins, protein phosphatase 1 inhibition assay, high performance liquid chromatography (HPLC)