Weijun Kong

Mechanisms of antifungal and anti-aflatoxigenic properties of essential oil derived from turmeric (Curcuma longa L.) on Aspergillus flavus.

The antifungal activity and potential mechanisms in vitro as well as anti-aflatoxigenic efficiency in vivo of natural essential oil (EO) derived from turmeric (Curcuma longa L.) against Aspergillus flavus was intensively investigated. Based on the previous chemical characterization of turmeric EO by gas chromatography-mass spectrometry, the substantially antifungal activities of turmeric EO on the mycelial growth, spore germination and aflatoxin production were observed in a dose-dependent manner. Furthermore, these antifungal effects were related to the disruption of fungal cell endomembrane system including the plasma membrane and mitochondria, specifically i.e. the inhibition of ergosterol synthesis, mitochondrial ATPase, malate dehydrogenase, and succinate dehydrogenase activities. Moreover, the down-regulation profiles of turmeric EO on the relative expression of mycotoxin genes in aflatoxin biosynthetic pathway revealed its anti-aflatoxigenic mechanism. Finally, the suppression effect of fungal contamination in maize indicated that turmeric EO has potential as an eco-friendly antifungal agent.

High-throughput determination of multi-mycotoxins in Chinese yam and related products by ultra fast liquid chromatography coupled with tandem mass spectrometry after one-step extraction

A simple, accurate and sensitive ultra fast liquid chromatography coupled with tandem mass spectrometry (UFLC-MS/MS) method was developed for high-throughput determination of aflatoxins (AFB1, AFB2, AFG1 and AFG2), ochratoxin A (OTA), fumonisins (FB1 and FB2) and zearalenone (ZEA) in Chinese yam, yam flours and yam-derived products. Mycotoxins were extracted from the samples with methanol-water-formic acid (79:20:1, v/v/v) and no further cleanup step before analysis. After optimization of some crucial parameters including sample preparation, chromatographic separation and MS/MS conditions, the method was successfully validated to exhibit excellent performance in terms of satisfactory linearity (r≥0.9977), limits of detection (≤0.15ngmL(-1)) and quantification (≤0.5ngmL(-1)) with good precision (RSD for intra- and inter-day variations of ≤4.65% and 6.31%, respectively), good accuracy (recoveries of 71.0-106.0%) and robustness, together with short run time (8min/sample). The developed method was applied for simultaneous detection and quantification of the above 8 mycotaxins in 27 batches of Chinese yam and related products collected from different markets and pharmacies in China. The results revealed that 1 normal sample and 4 moldy samples were found to be contaminated with different mycotoxins. The detected concentrations of AFB1 in 2 moldy samples exceeded the regulatory maximum residue levels. The proposed method was capable for simultaneous determination of mycotoxins in this and other types of complex matrices.

Assessment of critical points and development of a practical strategy to extend the applicable scope of immunoaffinity column cleanup for aflatoxin detection in medicinal herbs

Although extraction methods based on immunoaffinity column (IAC) cleanup have been used to detect aflatoxins in medicinal herbs, they do not yield satisfactory results for all sample matrices. The difficulty arises from the chemical complexity of the herbs, and there is a pressing need to determine which steps in IAC cleanup limit the scope of aflatoxin detection in many different kinds of medicinal herbs. In this work, we found that there were two main factors that severely decreased antibody-antigen recognition and led to serious nonspecific adsorption: (1) high extract acidity and (2) high co-extraction of interfering compounds. We therefore carried out a systematic study to optimize extraction efficiency. We found that dilution of samples in 0.1M phosphate buffer solution (pH 7.8, 2% Tween-20) at a 1:8 dilution ratio mitigated the effect of high acidity, decreased co-precipitation of compounds and nonspecific adsorption, and ameliorated the matrix effect. To validate this finding, and test if our method is widely applicable to in different kinds of herbal materials, we analyzed several representative complex sample matrices including fructus, cortex, and radix with varying extract pH values. The recovery efficiency was generally higher than 70%. We further validated our method by testing a certified reference material, and found that our approach accurately quantified aflatoxin concentration. After validation, we successfully used this method to determine the aflatoxin concentration of real samples. The approach described here could potentially be used to extract aflatoxin from other complex matrices with varying acidity.

UFLC-ESI-MS/MS analysis of multiple mycotoxins in medicinal and edible Areca catechu

A robust, sensitive and reliable ultra fast liquid chromatography combined with electrospray ionization tandem mass spectrometry (UFLC-ESI-MS/MS) was optimized and validated for simultaneous identification and quantification of eleven mycotoxins in medicinal and edible Areca catechu, based on one-step extraction without any further clean-up. Separation and quantification were performed in both positive and negative modes under multiple reaction monitoring (MRM) in a single run with zearalanone (ZAN) as internal standard. The chromatographic conditions and MS/MS parameters were carefully optimized. Matrix-matched calibration was recommended to reduce matrix effects and improve accuracy, showing good linearity within wide concentration ranges. Limits of quantification (LOQ) were lower than 50 μg kg(-1), while limits of detection (LOD) were in the range of 0.1-20 μg kg(-1). The accuracy of the developed method was validated for recoveries, ranging from 85% to 115% with relative standard deviation (RSD) ≤14.87% at low level, from 75% to 119% with RSD ≤ 14.43% at medium level and from 61% to 120% with RSD ≤ 13.18% at high level, respectively. Finally, the developed multi-mycotoxin method was applied for screening of these mycotoxins in 24 commercial samples. Only aflatoxin B2 and zearalenone were found in 2 samples. This is the first report on the application of UFLC-ESI(+/-)-MS/MS for multi-class mycotoxins in A. catechu. The developed method with many advantages of simple pretreatment, rapid determination and high sensitivity is a proposed candidate for large-scale detection and quantification of multiple mycotoxins in other complex matrixes.

Quantitative and fingerprinting analysis of Pogostemon cablin based on GC-FID combined with chemometrics.

In this study, a simple, sensitive and reliable gas chromatography-flame ionization detection (GC-FID) method is established for quantitative chemical fingerprinting of essential oils from Pogostemon cablin. Oil samples are prepared by hydrodistillation, with yields ranging from 0.73% to 2.02%. The two main components of the oil, patchouli alcohol and pogostone, were detected simultaneously in 36 samples and were found to have average contents of 43.07% and 7.84%, respectively. The method was validated in terms of linearity, sensitivity, precision, stability, and accuracy. All calibration curves showed excellent linearity (r(2)>0.9992) within the test ranges, and the relative standard deviation (RSD) values for intra- and inter-day precision were less than 1.5%, indicating a high degree of precision. The GC-FID chemical fingerprints of the 36 samples were established using 12 common peaks which account for over 90% of the total peak area. Chemometric techniques, including similarity analysis and hierarchical cluster analysis, were also employed to explore the similarities and outstanding consistencies among different P. cablin oil samples. The results demonstrate that chromatographic fingerprinting and quantitative analysis can be achieved simultaneously when evaluating quality and authenticating samples of P. cablin.

An indirect competitive fluorescence assay for ochratoxin A based on molecular beacon

A novel, simple and efficient method based on a molecular beacon (MB) probe was developed to detect ochratoxin A (OTA) in malts, which is a common starting material in the brewery industry. With the critical site for OTA binding in capture aptamer in mind, a MB probe containing 20 bases with a fluorophore–quencher pair at the stem ends was designed and synthesized. In the “off” configuration, the fluorescein (FAM) is internally quenched due to close contact with dabcyl and the fluorescence signal is recovered after hybridization with the capture aptamer at the “on” state. In the presence of OTA, the MB probe competes for binding at the loop region of the aptamer, resulting in a decrease in fluorescence signal. Using this indirect competitive assay, the detection of OTA in malt samples was accomplished for the first time. In addition, the effect of binding affinity of the capture aptamer and OTA on the assay performance was investigated. Under optimal conditions, this method allowed for OTA detection at a linear range of 0.0001–1 μg mL−1 (correlation coefficient, R = 0.9920) with superior sensitivity and a detection limit as low as 0.05 ng mL−1. The sensing system also displayed an excellent selectivity and perfect anti-interference capacity in the matrix. Moreover, the entire process of detection was accomplished in less than 20 min. The recovery from spiked malt samples ranged from 81.0% to 95.2% with RSDs below 5.4%. The performance of our method was further validated by ultra-fast liquid chromatography coupled with tandem mass spectrometry. Compared with similar fluorescence assays, the proposed method is simple, efficient and does not require complicated conjugation steps. Taken together, this novel detection strategy could be a promising tool for hand-held devices used during on-site monitoring of contaminants.

Simultaneous determination of four aflatoxins and ochratoxin A in ginger after inoculation with fungi by ultra-fast liquid chromatography–tandem mass spectrometry

BACKGROUNDnAflatoxins (AFs) and ochratoxin A (OTA) have been detected frequently in food, agricultural products and traditional Chinese medicines, and their presence poses serious health and economic problems worldwide. Ginger can easily be polluted with mycotoxins. In this study, ginger samples were cultivated for 15 days after inoculation with fungi and were prepared based on ultrasound-assisted solid-liquid extraction using methanol/water followed by immunoaffinity column clean-up and analysed by ultra-fast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS) for AFs and OTA.nnnRESULTSnThe limits of detection and quantification of AFs and OTA were 0.04-0.30u2009µg mL(-1) and 0.125-1.0u2009µg mL(-1) , respectively. The recoveries were 82.0-100.2%. After 15 days cultivation, no macroscopic mildew was found in ginger. But, the content of AFB1 expressed an increasing trend in ginger, peel [less than the limit of quantification (LOQ)] to the innermost layer (51.86u2009µ mL(-1) ), AFB2 was only detected in the innermost layer at the level of 0.87u2009µ mL(-1) . A small amount (<LOQ) of OTA was found in the peel of ginger after the two fungi were inoculated on the surface of ginger.nnnCONCLUSIONnThe developed method was successfully applied to analyse five mycotoxins, and has many advantages including rapid determination and high sensitivity. Meanwhile, in practice, more attention should be paid to the safety and quality of ginger.

Quantitative and fingerprinting analysis of Atractylodes rhizome based on gas chromatography with flame ionization detection combined with chemometrics.

This study assessed the feasibility of gas chromatography with flame ionization detection fingerprinting combined with chemometrics for quality analysis of Atractylodes rhizome. We extracted essential oils from 20 Atractylodes lancea and Atractylodes koreana samples by hydrodistillation. The variation in extraction yields (1.33-4.06%) suggested that contents of the essential oils differed between species. The volatile components (atractylon, atractydin, and atractylenolide I, II, and III) were quantified by gas chromatography with flame ionization detection and confirmed by gas chromatography with mass spectrometry, and the results demonstrated that the number and content of volatile components differed between A. lancea and A. koreana. We then calculated the relative peak areas of common components and similarities of samples by comparing the chromatograms of A. lancea and A. koreana extracts. Also, we employed several chemometric techniques, including similarity analysis, hierarchical clustering analysis, principal component analysis, and partial least-squares discriminate analysis, to analyze the samples. Results were consistent across analytical methods and showed that samples could be separated according to species. Five volatile components in the essential oils were quantified to further validate the results of the multivariate statistical analysis. The method is simple, stable, accurate, and reproducible. Our results provide a foundation for quality control analysis of A. lancea and A. koreana.

UFLC-MS/MS analysis of four tanshinone components in Salvia miltiorrhizae after ultrasound-assisted extraction.

A sensitive and rapid ultra-fast liquid chromatography with tandem mass spectrometry (UFLC-MS/MS) method was developed for simultaneous qualitative and quantitative of four characteristic tanshione components including tanshinone IIA, cryptotanshinone, tanshinone I and dihydrotanshinone I in Salvia miltiorrhizae after ultrasound-assisted extraction. By using a C18 column, the four analytes were separated by gradient elution with acetonitrile and water both containing 0.1% formic acid at the flow rate of 0.3mL/min. Multiple-reaction monitoring (MRM) was used for quantification, and an information-dependent acquisition (IDA) method was used to trigger enhanced product ion scans (EPI) for supplementary characteristic identification for qualitative research. Calibration curves showed good linearities with correlation coefficients (r) higher than 0.9990. The method showed high sensitivity with limits of detection (LODs) and quantification (LOQs) less than 0.0002ng/mL and 0.0008ng/mL, respectively, as well as good precision and reproducibility. Mean recoveries for four analytes ranged from 92.5% to 106.2% with relative standard deviations (RSDs) lower than 14.59%. Real application of the developed method in 32 batches of S. miltiorrhizae samples demonstrated that the total contents of four analytes in all samples were in the range of 2.258-52.342mg/g. Ultrasound-assisted extraction technique took a small amount of sample and low time but giving high extraction efficiency. Combining with UFLC-MS/MS method in MRM-IDA-EPI mode, more components in other complicated matrices can be simultaneously analyzed for qualitation and quantitation in one run.

Evaluation and quantitative analysis of 11 compounds in Morinda officinalis using ultra high performance liquid chromatography and photodiode array detection coupled with chemometrics

Morinda officinalis (Rubiaceae) is a traditional Chinese medicine widely used for the treatment of impotence and osteoporosis in clinical therapy. In the present study, a rapid and simple ultra-high performance liquid chromatography with photodiode array detection method was developed and validated for the simultaneous determination of 11 bioactive compounds in M. officinalis. This assay method was validated with respect to linearity (R2xa0 >xa00.9991), precision, repeatability, limit of detection, limit of quantification, and accuracy (with observed recovery rates between 94.21 and 100.38%). The quantitative results revealed significant differences in the concentrations of the selected compounds. Additionally, chemometric methods, including hierarchical clustering analysis, principal component analysis, and partial least-squares discriminate analysis, were applied to compare and sort the 25 batches of M. officinalis samples based on the quantitative data of the analytes. All of the samples were clearly divided into two groups: the Hainan samples were successfully discriminated from the samples from other origins. Simultaneous determination of multiple compounds using the proposed method combined with chemometrics could be a viable strategy to compare and evaluate the quality of M. officinalis.