Chromatographic Evaluation and Characterization of Constituents of Sunflower Seed Extract Used as Food Additives.

Sunflower seed extract, an antioxidant agent registered on the List of Existing Food Additives in Japan, was evaluated using HPLC, and three common constituents were detected. These peaks were identified as monocaffeoylquinic acids (3-O-caffeoylquinic acid, 4-O-caffeoylquinic acid, and 5-O-caffeoylquinic acid [chlorogenic acid]). Upon scrutinizing other components, dicaffeoylquinic acids (isochlorogenic acids; 3,4-di-O-caffeoylquinic, 3,5-di-O-caffeoylquinic, and 4,5-di-O-caffeoylquinic acids) were also identified. Structures of two newly isolated compounds were determined to be 3-O-(3S-2-oxo-3-hydroxy-indole-3-acetyl)-5-O-caffeoylquinic and 4-O-(3S-2-oxo-3-hydroxy-indole-3-acetyl)-5-O-caffeoylquinic acids. To identify the components that contribute to the antioxidant activity of sunflower seed extract, we fractionated the food additive sample solution and examined the active fractions for 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity. Monocaffeoylquinic and dicaffeoylquinic acids showed high DPPH activity, including their contribution to the antioxidant activity of this food additive. DPPH radical scavenging activity of the new compounds showed almost the same value as that of the positive control, Trolox. Therefore, the contribution of these compounds was also considered.

Design, Synthesis, and Evaluation of Inhibitors of Hedgehog Acyltransferase.

Hedgehog signaling is involved in embryonic development and cancer growth. Functional activity of secreted Hedgehog signaling proteins is dependent on N-terminal palmitoylation, making the palmitoyl transferase Hedgehog acyltransferase (HHAT), a potential drug target and a series of 4,5,6,7-tetrahydrothieno[3,2-c]pyridines have been identified as HHAT inhibitors. Based on structural data, we designed and synthesized 37 new analogues which we profiled alongside 13 previously reported analogues in enzymatic and cellular assays. Our results show that a central amide linkage, a secondary amine, and (R)-configuration at the 4-position of the core are three key factors for inhibitory potency. Several potent analogues with low- or sub-µM IC50 against purified HHAT also inhibit Sonic Hedgehog (SHH) palmitoylation in cells and suppress the SHH signaling pathway. This work identifies IMP-1575 as the most potent cell-active chemical probe for HHAT function, alongside an inactive control enantiomer, providing tool compounds for validation of HHAT as a target in cellular assays.

Application of the relative molar sensitivity method using GC-FID to quantify safranal in saffron (Crocus sativus L.).

Safranal is one flavor component of saffron, which is used as a spice, food additive, and crude drug. In ISO3632, safranal is defined as the compound that contributes to the quality of saffron, and many quantitative determination methods for safranal have been reported. However, safranal is volatile and degrades easily during storage, and an analytical standard with an exact known purity is not commercially available, making it difficult to quantify accurately the content of safranal in saffron. Here, we developed a method for quantifying safranal using relative molar sensitivity (RMS), called the RMS method, using a GC-flame ionization detector (GC-FID). We determined the RMS of safranal to 1,4-bis(trimethylsilyl)benzene-d4, a certified reference material commercially available, by a combination of quantitative NMR and chromatography. Using two GC-FID instruments made by different manufacturers to evaluate inter-instrument effect, the resultant RMS was 0.770, and the inter-instrument difference was 0.6%. The test solution, with a known safranal concentration, was measured by the RMS method, with an accuracy of 99.4-101%, repeatability of 0.81%, and reproducibility of 0.81-1.3%. Given the ease of degradation, high volatility, and uncertain purity of safranal reagents, the RMS method is a more accurate quantification approach compared to the calibration curve method and methods based on absorption spectrophotometry. Moreover, our findings revealed that the GC-FID makeup gas affected the RMS and quantitative values.

A new single-reference quantitative method using liquid chromatography with relative molar sensitivity based on 1H-qNMR for khellactone esters from Peucedanum japonicum root extract.

Khellactone ester (KLE) quantification using the absolute calibration method is difficult owing to the unavailability of standard reagents that can guarantee purity. Herein, a new method was developed to quantify KLEs from Peucedanum japonicum root extracts using liquid chromatography (LC) without utilizing standards. This method used relative molar sensitivity (RMS) and 7-ethoxy-4-methylcoumarin as a single-reference (SR) compound instead of KLE standards. RMS is the sensitivity ratio of SR to analytes, determined using an offline combination of quantitative NMR and LC. LC was performed using a triacontylsilyl silica gel column of superficially porous particles with a ternary mobile phase. The range of the method was 2.60-509 µmol/L. The accuracy and precision were reasonable. This is the first study to apply the RMS method to both conventional LC and ultra-high-performance liquid chromatography using the same mobile phase and column. This method may aid the quality assurance of foods containing KLEs.

[Proposal for Guidelines on the Notation and Investigation of Scientific Names for the Source of Natural Food Additives in Japanese Standards].

The official specifications for food additives from natural sources list the species according to their scientific and Japanese names, thereby providing a unique identifier for the species. This helps to prevent the use of nonprescribed species, which might cause unexpected or unintended health hazards. However, there are cases in which the names of the source species listed in the official specifications differ from the accepted scientific names based on the latest taxonomic research. In this paper, we argue that it is more important to define scientific and Japanese names with an emphasis on traceability in order to control the range of food additive ingredients in a rational and sustainable manner. Therefore, we proposed a method for ensuring traceability as well as a specific notation procedure for scientific and Japanese names. Using this method, we examined the source species for three food additives. In some cases, the range of sources species expanded with the change in scientific names. Ensuring traceability is extremely important, but it is also necessary to confirm whether unexpected species are included when names are changed.

Genetic identification of the original plant species for Mentha Herb listed in the Japanese Pharmacopoeia and analyses of their essential oil composition.

Mentha arvensis Linné var. piperascens Malinvaud is an original plant species for "Mentha Herb (Hakka, ハッカ)" and "Mentha Oil (Hakka-yu, ハッカ)" listed in the Japanese Pharmacopoeia, whereas Mentha canadensis L. is that of "Mint oil, partly dementholised" listed in the European Pharmacopoeia. Although these two species are thought to be taxonomically identical, there are no data on whether the source plants of the Mentha Herb products distributed in the Japanese market are actually M. canadensis L. This is an important issue for international harmonization of the Japanese Pharmacopoeia and European Pharmacopoeia. In this study, 43 Mentha Herb products collected from the Japanese market and two plant samples of the original species of Japanese Mentha Herb harvested in China were identified by sequence analyses of the rpl16 regions in the chloroplast DNA, and the composition of their ether extracts was analyzed by GC-MS. Almost all samples were identified as M. canadensis L., and the main component of their ether extracts was menthol, although there were variations in their composition. However, there were some samples thought to be derived from other Mentha species, even though their main component was menthol. For quality control of Mentha Herb, it is important to be sure of not only the original plant species but also the composition of the essential oil and amount of menthol as the characteristic compound.

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.

We report on the recommendation of the simple and versatility of methylated reference (MR) to improve applications in the single reference (SR)-LC based on relative molar sensitivity (RMS). Three curcuminoids (Curs) such as curcumin, demethoxycurcumin and bisdemethoxycurcumin in turmeric products were determined using authentic standards and methylated curcumin. In addition, high-speed countercurrent chromatography (HSCCC) purification is necessary to separate Curs for indicating the RMS. For HSCCC separation, a biphasic solvent system was used to obtain these fractions, which were then subjected to 1H quantitative NMR to determine their contents in each test solution. Using these solutions, the RMS of Curs are calculated from slopes ratios of calibration curves (three ranges from 0-100 µmol/L, r2 > 0.998). The averaged RMS of Curs were 8.92 (relative standard deviation (RSD), 1.17%), 8.97 (2.18%), and 9.61 (0.77%), respectively. Cur concentrations in turmeric products can be determined using RMS, peak area, and MR content added in these samples. This proposed method, which is based on chemical methylation and the SR-LC assay has been successfully applied for the simple and reliable estimation of Curs in turmeric products.

[Determination of Allyl Isothiocyanate in Mustard and Horseradish Extracts by Single Reference GC and HPLC Based on Relative Molar Sensitivities].

The main component of the Mustard and Horseradish extracts, which are used as natural food additives in Japan, is allyl isothiocyanate (AITC). The determination of AITC using GC-FID is the official method employed in the quality control assessments for these products. In this method, a commercially available AITC reagent is used as a calibrant. However, 1H-quantitative NMR (qNMR) analysis revealed that the AITC reagents contain impurity. Therefore, we examined the GC-FID and HPLC-refractive index detector (LC-RID) method based on relative molar sensitivities (RMSs) to high-purity single reference (SR). The RMSs of AITC/SR under the GC-FID and LC-RID conditions were accurately determined using qNMR. The AITC in two types of food additives was quantified using qNMR, SR GC-FID, and SR LC-RID methods. Both SR GC-FID and SR LC-RID showed good agreement within 2% with the AITC content determined by direct qNMR.

Molecular Structure of Gardenia Blue Pigments by Reaction of Genipin with Benzylamine and Amino Acids.

Genipin was reacted with benzylamine and several amino acids to prepare gardenia blue (GB). The time-course of GB formation with benzylamine was monitored by high-performance liquid chromatography (HPLC), liquid chromatography time-of-flight mass spectrometry (LC-TOFMS), and 1H and 13C NMR measurements. In this experiment, we determined the molecular structures of some intermediates using accurate masses and additional NMR techniques such as heteronuclear multiple bond correlation (HMBC). GBs with amino acids (GB-AAs) were characterized by both liquid and solid-state NMR measurements. Interestingly, many significant peaks appeared in the solid-state NMR spectra, although the 13C NMR spectra from solution samples did not show any distinct peaks. Therefore, we determined that GB-AAs had an alternating copolymer structure composed of methyne and 5H-2-pyrindine, which was substituted by amino acids at N atom and linked with methyne at 5 and 7 positions. To confirm this molecular structure, the pyrolysis gas chromatography-mass spectrometry (GC-MS) measurement of GB-AAs was carried out, and 5H-2-pyrindine and its methyl derivatives were formed as main pyrolysis products from the polymer chains.

Determination of Mogroside V in Luohanguo Extract for Daily Quality Control Operation Using Relative Molar Sensitivity to Single-Reference Caffeine.

Mogroside V is one of the characteristic and effective components of luohanguo extract, a food additive used as a sweetener in Japan as per Japan's Standards and Specifications for Food Additives (JSFA; 9th ed.). JSFA stipulates that the quantitative determination for mogroside V content in luohanguo extract applies HPLC using analytical standard mogroside V. However, no mogroside V reagents with proven purities are commercially available. Therefore the current JSFA determination method is not particularly suited for daily quality control operations involving luohanguo extract. In this study, we applied an alternative quantitative method using a single reference with relative molar sensitivity (RMS). It was possible to calculate the accurate RMS by an offline combination of 1H-quantitative NMR spectroscopy (1H-qNMR) and an HPLC/variable-wavelength detector (VWD). Using the RMS of mogroside V to a commercial certified reference material grade caffeine, the mogroside V contents in luohanguo extracts could be determined using HPLC/VWD without analytical standard mogroside V. There was no significant difference between the mogroside V contents in luohanguo extracts determined using the method employing single-reference caffeine with the RMS and using the JSFA method. The absolute calibration curve for the latter was prepared using an analytical standard mogroside V whose purity was determined by 1H-qNMR. These results demonstrate that our proposed method using a single reference with RMS is suitable for quantitative determination of mogroside V in luohanguo extract and can be used as an alternative method to the current assay method in JSFA.

Quantification of tea-derived catechins without the requirement for respective calibration curves by single reference liquid chromatography based on relative molar sensitivity.

BACKGROUND: Many studies report the monitoring of catechins in tea samples by chromatographic techniques. Unfortunately, only a small number of screening assays for catechins exist as a result of the complexity of authentic standards for the respective calibration curves. In the present study, a single reference (SR) exhaustive assay for the simultaneous quantification of tea-derived catechins by liquid chromatography (LC) with photodiode array and fluorescence detectors based on relative molar sensitivity (RMS) was developed as a screening assay of common tea samples without respective calibration curves using authentic standards. RESULTS: Three original SR standards were proposed based on flavonoid structures, evaluated by quantitative 1 H-NMR based on an indirect standard (1,4-bis(trimethylsilyl) benzene-d4 ) and successfully separated in a LC chromatogram. In tea samples with these added SR calculated based on RMS, the concentrations of eight tea-derived catechins could be measured with a relative SD of < 8.5% by a single LC run. CONCLUSION: This LC screening assay based on RMS allows reliable quantification without the requirement for respective calibration curves using authentic standards. © 2020 Society of Chemical Industry.

Use of Relative Molar Sensitivity as a Specific Value for Evaluating Heptaoxyethylene Dodecyl Ether Concentrations in Methanol Solution.

Relative molar sensitivity (RMS) determined using quantitative 1H NMR and HPLC with a refractive index (RI) detector was applied as a specific value for quantifying the levels of heptaoxyethylene dodecyl ether (HOEDE), a typical non-ionic surfactant, in methanol solutions. RMS was robust against changes of the analytical conditions (i.e., RI cell temperature, acetonitrile content in the mobile phase, HPLC system). Furthermore, the obtained HOEDE concentrations using a previously evaluated RMS were comparable to those obtained using a reference method for over 1 year.

Development of an HPLC method with relative molar sensitivity based on 1H-qNMR to determine acteoside and pedaliin in dried sesame leaf powders and processed foods.

A high-performance liquid chromatography (HPLC) method with relative molar sensitivity (RMS) based on 1H quantitative NMR spectroscopy (1H-qNMR) has been developed for food ingredients such as acteoside (verbascoside) and pedaliin (pedalitin-6-O-glucoside) without requiring authentic and identical standards as the reliable analytical methods. This method is used methyl 4-hydroxybenzoate (MHB) as an alternative reference standard. Each RMS is also calculated from the ratio of each analyte's molar absorption coefficient to that of MHB after correcting the purities of the analytes and reference standard by 1H-qNMR. Therefore, this method can quantify several analytes with metrological traceability to the International System of Units (SI) using the RMS and one alternative reference standard. In this study, the content of acteoside and pedaliin in several samples, such as dried sesame leaf powders and commercially processed foods, can be determined by the proposed RMS method and demonstrated in good agreement that obtained by a conventional method. Moreover, the proposed method yields analytical data with SI-traceability without the need for an authentic and identical analyte standard. Thus, the proposed RMS method is a useful and practical tool for determining acteoside and pedaliin in terms of the accuracy of quantitative values, the routine analysis, and the cost of reagents.

A 90-day repeated oral dose toxicity study of four stereoisomers of 2,4-dimethyl-4-phenyltetrahydrofuran, a synthetic flavoring substance, in F344 rats.

2,4-Dimethyl-4-phenyltetrahydrofuran (CAS no. 82461-14-1) is a food additive used as a synthetic flavoring substance. To investigate the toxicological properties and determine the no-observed-adverse-effect level (NOAEL), a 90-day repeated oral dose toxicity study of 2,4-dimethyl-4-phenyltetrahydrofuran containing four stereoisomers was conducted in F344 rats at doses of 0, 6, 24, and 96 mg/kg body weight (BW)/day. No mortality or abnormal clinical signs related to treatment in any group was observed. At a dose of 96 mg/kg BW, fluctuated serum total protein and total cholesterol and increased absolute and relative liver weights and relative kidney weights were observed in both sexes. Increased serum albumin in males and decreased Na and Cl in females were also observed. On histopathological assessment, at a dose of 96 mg/kg BW, diffuse hepatocellular hypertrophy in the liver in both sexes and tubular regeneration with scattered proximal tubular degeneration and/or necrosis throughout the cortex in the kidney in males were detected. Based on these findings, the NOAEL for 2,4-dimethyl-4-phenyltetrahydrofuran used in the current study was found to be 24 mg/kg BW/day for both sexes.

Determination of perillaldehyde in perilla herbs using relative molar sensitivity to single-reference diphenyl sulfone.

Perillaldehyde (PRL) is one of the essential oil components derived from perilla plants (Perilla frutescens Britton) and is a characteristic compound of the traditional medicine "perilla herb ()" listed in the The Japanese Pharmacopoeia, 17th edition (JP17). HPLC using an analytical standard of PRL has been used to quantitatively determine the PRL content in perilla herb. However, PRL reagents have been reported to decompose easily. In this study, we utilized an alternative quantitative method using on a single reference with relative molar sensitivity (RMS) based on the results of experiments performed in two laboratories. It was possible to calculate the exact RMS using an offline combination of 1H-quantitative NMR spectroscopy (1H-qNMR) and an HPLC/photodiode array (PDA) detector (or an HPLC/variable-wavelength detector [VWD]). Using the RMS of PRL to the single-reference compound diphenyl sulfone (DFS), which is an inexpensive and stable compound, the PRL content in the perilla herb could be determined using HPLC/PDA or HPLC/VWD without the need for the analytical standard of PRL. There was no significant difference between the PRL contents of perilla herb determined using the method employing the single-reference DFS with RMS and using the JP17 assay, the calibration curve of which was generated using the analytical standard of PRL with adjusted purity measured by 1H-qNMR. These results demonstrate that our proposed method using a single reference with RMS is suitable for quantitative assays of perilla herb and can be an alternative method for the current assay method defined in the JP17.

Relative molar sensitivities of carnosol and carnosic acid with respect to diphenylamine allow accurate quantification of antioxidants in rosemary extract.

We have been developing a high-performance liquid chromatography/photodiode array (HPLC/PDA) employing relative molar sensitivities (RMSs) and adopted it to the accurate quantification of carnosol (CL) and carnosic acid (CA) which are the antioxidants in rosemary extract. The method requires no references of CL or CA and instead uses RMSs with respect to diphenylamine (DPA) whose certified reference material is available from a reagent manufacturer. The molar and response ratios of the analytes to the reference in an artificial mixture of them were determined using 1H-quantitative nuclear magnetic resonance spectroscopy (1H-qNMR) and HPLC/PDA at a wavelength of 284 nm under isocratic condition, respectively, and then RMSs were calculated to be 0.111 for CL/DPA and 0.0809 for CA/DPA as averaged values in three HPLC-PDA instruments. The RMS values varied by up to 1.1% as relative standard deviation. To evaluate the performance of HPLC/PDA with the RMSs, the CL and CA contents in rosemary extracts were determined using DPA as a reference. The CL and CA contents were compared with those determined using calibration curves of CL and CA obtained by HPLC measurement of standard solutions prepared from their reagents whose absolute purities were determined using 1H-qNMR. The differences between the two methods for CL and CA were ≤3% as relative error. This chromatographic method with RMSs allows a simple and reliable quantification when reference of the analyte is unavailable.

[Quantitative Analysis of Piperine and the Derivatives in Long Pepper Extract by HPLC Using Relative Molar Sensitivity].

A novel method was developed for quantification of five major piperine derivatives (piperanine, piperine, chavicine, isopiperine, and isochavicine) in a hot water extract of long pepper fruit (LPE) using the relative molar sensitivity (RMS) based on the combination of HPLC/UV and 1H- quantitative NMR (1H-qNMR). The RMSs of piperanine, chavicine, isopiperine, and isochavicine to piperine of which the absolute purity was determined by 1H-qNMR were calculated to be 0.3693, 1.138, 0.9164, and 1.277, respectively. The total amount of piperine derivatives in LPE was quantified by both 1H-qNMR and HPLC/UV based on the RMS using piperine as a single-reference material (RMS method). The relative difference in quantitation values of 1H-qNMR and calibration curve method from the RMS method was 2.01% or less. The relative difference of the total cis-trans piperine isomers content between before and after photoirradiation in piperine solution was quantified to be 2.84% by the RMS method. In addition, the interlaboratory difference of the RMS method was confirmed in the range of 0.600 to 4.00 µg/g when analysis was performed on piperine derivatives in LPE containing tablets, while the total amount of piperine derivatives in the tablets was quantified at 606 µg/g. Our proposed method is a reliable tool for determining the contents of piperine and the derivatives in LPE and processed foods containing LPE.

[Determination of Hesperidin and Monoglucosylhesperidin Contents in Processed Foods Using Relative Molar Sensitivity Based on 1H-Quantitative NMR].

We designed an off-line combination of HPLC/photodiode array detector (PDA) and 1H-quantitative NMR (1H-qNMR) to estimate the relative molar sensitivity (RMS) of an analyte to a reference standard. The RMS is calculated as follows: a mixture of the analyte and the reference is analyzed using 1H-qNMR and HPLC/PDA. The response ratio of the analyte and the reference obtained by HPLC/PDA is then corrected using the molar ratio obtained by 1H-qNMR. We selected methylparaben (MPB), which is a certified reference material, as the reference standard and hesperidin (Hes) and monoglucosylhesperidin (MGHes) as analytes, and the RMSs of Hes283 nm/MPB255 nm and MGHes283 nm/MPB255 nm were determined as 1.25 and 1.32, respectively. We determined the contents of Hes and MGHes in processed foods by the conventional absolute calibration method and by the internal standard method employing the RMS values with respect to MPB. The differences between the values obtained with the two methods were less than 2.0% for Hes and 3.5% for MGHes.

Preliminary Quality Evaluation and Characterization of Phenolic Constituents in Cynanchi Wilfordii Radix.

A new phenolic compound, 2-O-ß-laminaribiosyl-4-hydroxyacetophenone (1), was isolated from Cynanchi Wilfordii Radix (CWR, the root of Cynanchum wilfordii Hemsley), along with 10 known aromatic compounds, including cynandione A (2), bungeisides-C (7) and -D (8), p-hydroxyacetophenone (9), 2',5'-dihydroxyacetophenone (10), and 2',4'-dihydroxyacetophenone (11). The structure of the new compound (1) was elucidated using spectroscopic methods and chemical methods. The structure of cynandione A (2), including a linkage mode of the biphenyl parts that remained uncertain, was unambiguously confirmed using the 2D 13C-13C incredible natural abundance double quantum transfer experiment (INADEQUATE) spectrum. Additionally, health issues related to the use of Cynanchi Auriculati Radix (CAR, the root of Cynanchum auriculatum Royle ex Wight) instead of CWR have emerged. Therefore, constituents present in methanolic extracts of commercially available CWRs and CARs were examined using UV-sensitive high-performance liquid chromatography (HPLC), resulting in common detection of three major peaks ascribed to cynandione A (2), p-hydroxyacetophenone (9), and 2',4'-dihydroxyacetophenone (11). Thus, to distinguish between these ingredients, a thin-layer chromatography (TLC) method, combined with only UV irradiation detection, focusing on wilfosides C1N (12) and K1N (13) as marker compounds characteristic of CAR, was performed. Furthermore, we propose this method as a simple and convenient strategy for the preliminary distinction of CWR and CAR to ensure the quality and safety of their crude drugs.

HPLC/PDA determination of carminic acid and 4-aminocarminic acid using relative molar sensitivities with respect to caffeine.

To accurately determine carminic acid (CA) and its derivative 4-aminocarminic acid (4-ACA), a novel, high-performance liquid chromatography with photodiode array detector (HPLC/PDA) method using relative molar sensitivity (RMS) was developed. The method requires no analytical standards of CA and 4-ACA; instead it uses the RMS values with respect to caffeine (CAF), which is used as an internal standard. An off-line combination of 1H-quantitative nuclear magnetic resonance spectroscopy (1H-qNMR) and HPLC/PDA was able to precisely determine the RMSs of CA274nm/CAF274nm and 4-ACA274nm/CAF274nm. To confirm the performance of the HPLC/PDA method using RMSs, the CA and 4-ACA contents in test samples were tested using four different HPLC-PDA instruments and one HPLC-UV. The relative standard deviations of the results obtained from five chromatographs and two columns were less than 2.7% for CA274nm/CAF274nm and 1.1% for 4-ACA274nm/CAF274nm. The 1H-qNMR method was directly employed to analyse the CA and 4-ACA contents in test samples. The differences between the quantitative values obtained from both methods were less than 5% for CA and 3% for 4-ACA. These results demonstrate that the HPLC/PDA method using RMSs to CAF is a simple and reliable quantification method that does not require CA and 4-ACA certified reference materials.