Foreword

Food contains a variety of ingredients that have both beneficial and harmful effects on living organisms. The intake of beneficial substances in the foods can improve human health, but excessive intake can cause adverse side effects. On the other hand, consumption of food contaminated with harmful substances has been linked to the development of various diseases. From this point of view, the qualitative and quantitative analysis of active ingredients present in food is an important issue. Among analytical techniques, LC is particularly useful because it enables simultaneous determination of concentrations of many components and selective analysis of certain components separated from other interfering matrices. This Current Topics of Chemical and Pharmaceutical Bulletin contains one review article and five regular articles describing the latest research on the liquid chromatographic techniques utilized in the field of food science. These liquid chromatographic techniques include HPLC with UV detection, fluorescence detection, electrochemical detection (ECD) and MS.

The review article entitled “A Review on the Foodomics Based on Liquid Chromatography Mass Spectrometry” by Mr. Muguruma, Dr. Nunome and Prof. Inoue summarizes the recent trends and applications of metabolomics based on “foodomics” by LC-MS and provides the perspectives and insights into the methodology and various sample preparation techniques in food analysis. “Foodomics,” is the multi-“Omics” used to control food safety, quality, traceability, and hygiene management and to assess functional and nutritional factors in the field of food science. LC-MS has a great potential to study food and nutrition components, ranging from small molecules to huge proteins with high sensitivity, which is important in foodomics study. Furthermore, MS enables the simultaneous detection of various target analytes in complex food mixtures with an individual m/z value.

The first regular article entitled “Quantification of Casein in Baked Food Products by Selective Analysis of Phosphorylated Peptides Using Fluorous Derivatization with Liquid Chromatography-Tandem Mass Spectrometry Method” by Mr. Kawasue and Prof. Yoshida and colleagues, describes the determination method for casein in baked food products by liquid chromatography with tandem mass spectrometry (LC-MS/MS). LC-MS/MS is effective for both quantitative and qualitative analysis of food components, but there is a problem of ion suppression by matrix components. In this study, fragment peptides obtained by tryptic digestion of caseins were selected as target peptides. The phosphorylated serine residue in each peptide was converted to a perfluoroalkyl group by derivatization. The obtained fluorous-derivatized peptides were analyzed by LC-MS/MS, to which a fluorous LC column was connected. As the fluorous-derivatized phosphopeptides were selectively retained on a fluorous LC column, they could be detected without any interference from matrix components in the baked foods.

The second regular article entitled “Study on the Synthesis of Methylated Reference and Their Application in the Quantity of Curcuminoids Using Single Reference Liquid Chromatography Based on Relative Molar Sensitivity” by Dr. Takahashi and Prof. Inoue and colleagues, reports the versatility of methylated reference (MR) to improve applications in the single reference LC based on relative molar sensitivity. In this study, three curcuminoids such as curcumin, demethoxycurcumin and bisdemethoxycurcumin were evaluated by LC-UV using methylated curcumin as MR. It was indicated with MR that curcuminoids in various turmeric products were determined without respective calibration curves using authentic standards.

The third regular article entitled “Determination Method for Pyrroloquinoline Quinone in Food Products by HPLC-UV Detection Using a Redox-Based Colorimetric Reaction” by our research group, developed an HPLC method for the determination of pyrroloquinoline quinone (PQQ), which utilizes a redox-based colorimetric reaction. In this method, PQQ could be detected using a colorimetric reagent based on the redox cycle of quinone although the absorbance of PQQ itself was negligible. The method was applied successfully for the determination of PQQ in supplemental capsules, and also in juice samples.

The fourth regular article entitled “HPLC Fluorescence Method for Eugenols in Basil Products Derivatized with DIBI” by Dr. Takada and Prof. Wada and colleagues, describes a sensitive HPLC-fluorescence method for eugenols derivatized with fluorescent reagent, 4-(4,5-diphenyl-1H-imidazol-2-yl)iodobenzene (DIBI) based on the Mizoroki–Heck coupling reaction. HPLC-fluorescence is more sensitive than UV methods but requires derivatization of non-fluorescent compounds such as eugenols. This method was successfully used to analyze three eugenols in basil products without any interfering peaks.

The final regular article entitled “Determination of Phenolic Compounds in Beverages by Three-Flow Channel Isocratic HPLC with Electrochemical Detections Using a Column-Switching Technique” by Dr. Sun and Dr. Kotani et al., devises a three-flow channel isocratic HPLC with electrochemical detection (3LC-ECD) system using a column-switching technique for the quantitative analysis of phenolic compound. Phenolic compounds with significantly different hydrophobicity were simultaneously measured to draw three chromatograms by the 3LC-ECD without a gradient elution that interferes with the high-sensitive determination of redox compounds by HPLC-ECD. The 3LC-ECD system was demonstrated that the contents of the phenolic compounds in tea and wine samples with simple sample preparation procedures.

I believe that the review and research articles in this Current Topics provide useful suggestions to obtain valuable information of active ingredients in food samples. I would like to express my special thanks to all of the authors for their significant contributions to this Current Topics on food analysis.