Penicillic acid in fruits: method development, validation by liquid chromatography-tandem mass spectrometry and survey in southern China

BACKGROUND

Penicillic acid (PA) is produced by Aspergillus spp. and Penicillium spp., which are common postharvest and storage fungi of fruits. PA can be of concern for human health because of its toxicity and high fruit consumption by the population. However, no data on PA occurrence in various fruits have yet been reported. A quick, easy, cheap, effective, rugged and safe (QuEChERS) approach for PA determination in various fruits was developed and applied to explore PA incidence in fruits.

RESULTS

The modified QuEChERS procedure with extraction by ethyl acetate and purification by multi-walled carbon nanotubes (MWCNTs), primary secondary amine (PSA) and octadecyl silane (C18) was established to determine PA in various fruits by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The average recoveries were 72.9-102.2% and relative standard deviations (RSDs) were 1.3-7.9%. A total of 161 fruits samples, including kiwi, apple, peach, grape and mandarin/orange, were collected in southern China. The incidence of PA in fruits was 14.9% and the levels of PA contamination were 0.200-0.596 μg kg^-1 . Our results suggested that orange/mandarin, grape and kiwi were favorable matrices for Aspergillus spp. and Penicillium spp. to produce PA, rather than peach and apple.

CONCLUSION

To the best of our knowledge, this is the first report about PA contamination in various fruits in China. Our study emphasizes the necessity of the current established method, which could be used for continuous monitoring of PA and reducing the health risk to Chinese consumers. © 2020 Society of Chemical Industry.

Human pancreatic cancer cells under nutrient deprivation are vulnerable to redox system inhibition

Large regions in tumor tissues, particularly pancreatic cancer, are hypoxic and nutrient-deprived because of unregulated cell growth and insufficient vascular supply. Certain cancer cells, such as those inside a tumor, can tolerate these severe conditions and survive for prolonged periods. We hypothesized that small molecular agents, which can preferentially reduce cancer cell survival under nutrient-deprived conditions, could function as anticancer drugs. In this study, we constructed a high-throughput screening system to identify such small molecules and screened chemical libraries and microbial culture extracts. We were able to determine that some small molecular compounds, such as penicillic acid, papyracillic acid, and auranofin, exhibit preferential cytotoxicity to human pancreatic cancer cells under nutrient-deprived compared with nutrient-sufficient conditions. Further analysis revealed that these compounds target to redox systems such as GSH and thioredoxin and induce accumulation of reactive oxygen species in nutrient-deprived cancer cells, potentially contributing to apoptosis under nutrient-deprived conditions. Nutrient-deficient cancer cells are often deficient in GSH; thus, they are susceptible to redox system inhibitors. Targeting redox systems might be an attractive therapeutic strategy under nutrient-deprived conditions of the tumor microenvironment.

Antibacterial activities of penicillic acid isolated from Aspergillus persii against various plant pathogenic bacteria

The emergence of pathogenic bacterial strains resistant to agrochemicals and the increasing demand for organic foods have led to the discovery of new antibacterial metabolites that can be used either directly or as a lead molecule for development of synthetic bactericides. During the screening of antibacterial fungal cultures, we found that one fungal strain, Aspergillus persii EML-HPB1-11, showed strong in vitro antibacterial activity against Xanthomonas arboricola pv. pruni (Xap) with a minimum inhibitory concentration (MIC) of 10% of fermentation broth filtrate. The active compound was identified as penicillic acid (PA: 3-methoxy-5-methyl-4-oxo-2,5-hexadienoic acid) by mass and NMR spectroscopy. The in vitro antibacterial activity of PA was tested against 12 phytopathogenic bacteria. All of the bacterial pathogens tested were highly inhibited by PA with MIC values of 12·3-111·1 μg ml(-1) . It also effectively suppressed the development of bacterial spot disease in detached peach leaves, showing control values of 82·4 and 94·1% at concentrations of 111·1 and 333·3 μg ml(-1) respectively. This is the first report on the production of PA by A. persii. This study suggests that PA can be used as a lead molecule for development of synthetic bactericides for control of various plant diseases.

SIGNIFICANCE AND IMPACT OF THE STUDY

Penicillic acid (PA) produced by the seed-borne fungus Aspergillus persii EML-HPB1-11 showed antibacterial activity against various plant pathogenic bacteria. The compound effectively inhibited the growth of 12 plant pathogenic bacteria and successfully controlled bacterial spot disease on peach leaf. These results suggest that PA can be used as a lead molecule for development of synthetic agrochemicals to control plant bacterial diseases.

Production of the Fusarium Mycotoxin Moniliformin by Penicillium melanoconidium

Moniliformin is a mycotoxin produced by several cereal associated Fusaria. Here, we show for the first time that moniliformin can be produced by the cereal fungus, Penicillium melanoconidium (4 out of 4 strains), but not in the related species in the Viridicata series. Moniliformin was detected in 10 out of 11 media: two agars and several cereal and bean types. Moniliformin was identified by a novel mixed-mode anionic exchange reversed phase chromatographic method which was coupled to both tandem mass spectrometry (MS) and high resolution MS. Mixed-mode chromatography showed superior peak shape compared to that of HILIC and less matrix interference compared to that of reversed phase chromatography, but during a large series of analyses, the column was fouled by matrix interferences. Wheat and beans were artificially infected by P. melanoconidium containing up to 64 and 11 mg/kg moniliformin, respectively, while penicillic acid, roquefortine C, and penitrem A levels in wheat were up to 1095, 38, and 119 mg/kg, respectively.

Porcine/chicken or human nephropathy as the result of joint mycotoxins interaction

A survey was made of the literature concerning the occurrence and incidence of mycotoxic nephropathy in pigs and chicks in different countries. Various etiological factors contributing to the development of the disease were considered. The main nephrotoxic fungi as well as the specific conditions for their growth and toxins production were briefly described. A survey was made about the most frequent nephrotoxic fungal contaminants in various feedstuffs from plant origin. In addition, their natural quantities and importance for development of mycotoxic porcine/chick nephropathy (MPN/MCN) are also explored. In addition, a survey was made of the feedstuffs representing the most favorable environment for nephrotoxic fungal growth as well as the most favorable storehouse conditions for this fungal growth were shortly described. The significance of some underestimated fungal species, which can provoke kidney damage, was studied. The importance of joint mycotoxin interaction and newly identified fungal metabolites in the complex etiology of mycotoxic nephropathy ranged in some countries is deeply investigated. The toxicity of the low contamination levels of some combinations of mycotoxins often administered by pigs and chicks in the practice was carefully studied.

Complex etiology, prophylaxis and hygiene control in mycotoxic nephropathies in farm animals and humans

Various etiological factors contributing to the development of mycotoxic nephropathy in farm animals and humans are reviewed. The possible synergistic effect between ochratoxin A (OTA) and other mycotoxins, as penicillic acid (PA) and fumonisin B(1) (FB(1)), contributing to this nephropathy is also considered and discussed. The most convenient ways of prophylaxis and various preventive measures against OTA contamination of feeds or foods are reviewed. A reference is made concerning the most successful methods of veterinary hygiene control in the slaughterhouses in order to prevent the entering of OTA in commercial channels with a view to human health. The economic efficacy of these prophylactic procedures is also considered. An evaluation of human exposure to OTA is made.

Mutagenicity of 5,6-Dihydropenicillic Acid (DHPA) in Drosophila melanogaster and Bacterial Conversion of Penicillic Acid to DHPA

We studied the mutagenicity of 5,6-dihydropenicillic acid (DHPA) by means of the Drosophila wing-spot test. DHPA (10 mg/g of medium) significantly increased the number of small single and twin spots. Since twin spots were exclusively caused by mitotic crossing-over, the results demonstrated that DHPA can induce chromosome recombination in Drosophila somatic cells. Penicillic acid (PA) was converted to DHPA by an incubation with Agrobacterium radiobactor . The conversion occurred with other spoilage bacteria, such as Pseudomonas aeruginosa and P. cepacia . PA was completely converted to DHPA within a 24-h incubation with P. aeruginosa or P. cepacia in medium containing yeast extract. The results suggested that mutagenic DHPA is produced by environmental bacteria when foods are contaminated by fungi which produce PA.