Semicarbazide universality study and its speculated formation pathway

Depletion kinetics of semicarbazide in giant river prawn (Macrobrachium rosenbergii) following nitrofurazone oral administration and its occurrence in an aquaculture farm

Semicarbazide (SEM), a marker residue used to monitor the use of prohibited drug nitrofurazone (NFZ), is commonly found in wild crustaceans, implying the natural origin. However, the difference between endogenous and exogenous SEM has rarely been investigated. So, tissue-bound SEM was determined in samples collected from giant river prawns cultured in an aquaculture farm and in samples from an experiment where giant river prawns were fed twice a day with NFZ at 30 mg/kg for 5 days. At day 10 of drug withdrawal, muscle SEM of the NFZ-fed prawn was 17.78 ng/g and depleted to 1.18 ng/g at day 90 (half-life 20.31 days) which was significantly higher than the control prawn (usually ≤ 0.1 ng/g). In contrast, the average SEM in the shell was independent of NFZ treatment. SEM was not found in the aquaculture farm samples, implying that the SEM in cultured prawn did not originate from SEM contamination.

The presence of semicarbazide in crustaceans collected from natural habitats in Thailand

Semicarbazide (SEM) has been used as a marker residue of the banned veterinary drug nitrofurazone (NFZ). Although evidence indicates that SEM can be found in some natural crustaceans that have never been exposed to NFZ, such information is limited to a few species. The present study aimed to investigate the natural occurrence of SEM in wild crustaceans in Thailand. A total of 14 species, all economically important food animals, were captured from different regions of Thailand. Tissue-bound SEM and its parent drug NFZ were determined by the UPLC-MS/MS and LC-MS methods, respectively. The results showed that while NFZ was not detected in any samples, the tissue-bound SEM could be found in every natural crustacean species investigated. However, the prevalence and concentration varied greatly. The occurrence of SEM in the freshwater palaemonid Macrobrachium prawns is generally much higher than in the marine penaeid shrimps/prawns. SEM was found in 33% and 80% of the giant river prawn (Macrobrachium rosenbergii) muscles (<0.10-0.46 ng/g) and shells (3.68-13.22 ng/g), respectively. In contrast, SEM was not detected in the muscles of penaeid shrimps/prawns (with few exceptions), but it was occasionally found in the shells at low levels (usually <1 ng/g). The shells of saltwater crabs also contained higher levels of SEM than the muscles. For instance, the highest SEM levels detected in the mud crab (Scylla sp.) muscles and shells were 0.40 and 22.75 ng/g, respectively. However, the situation was reversed for the rice-field crab (Sayamia sp. and Esanthelphusa sp.), in which SEM was not detected in all shells but detected in the muscles (up to 1.46 ng/g). The fact that SEM is often found in wild crustaceans implies a natural origin of this substance. Consequently, using SEM as a marker residue of NFZ is controversial and should be reconsidered.

Presence of nitrofurans and their metabolites in gelatine

Following the detection of semicarbazide (SEM) in gelatine by Italian Authorities, at levels exceeding by three times the reference point for action (RPA) of 1 μg/kg, set out by Commission Regulation (EU) 2019/1871 for nitrofurans and their metabolites, the European Commission mandated EFSA to investigate the available sources of nitrofurans and their metabolites in gelatine. European Commission also asked EFSA to provide approaches that would distinguish SEM occurring due to illegal treatment with nitrofurazone from SEM produced during food processing. The literature indicates that SEM, both free and bound to macromolecules, could occur also in food products such as gelatine, during food processing, arising from the use of disinfecting agents and/or from reactions of various food components and, therefore, SEM cannot be considered as an unequivocal marker of the abuse of nitrofurazone in animal production. It is recommended to investigate in more detail which processing conditions lead to the formation of SEM in gelatine during its production and what levels can be found. One potential approach to distinguishing between SEM from nitrofurazone and SEM from other sources in food products, such as gelatine, might be based on determining the ratio of bound:free SEM in a sample of gelatine. However, whether the ratio of bound:free SEM would unequivocally distinguish between SEM arising from nitrofurazone abuse or from other sources still needs to be demonstrated.

Semicarbazide Accumulation, Distribution and Chemical Forms in Scallop (Chlamys farreri) after Seawater Exposure

Simple Summary

Semicarbazide is considered the characteristic metabolite of nitrofurazone and it is often used as a marker to monitor the illegal use of nitrofurazone in foods. Recent studies have indicated that semicarbazide pollution can be introduced in many ways and this compound is a newly recognized pollutant type in the environment that accumulates in aquatic organisms throughout the food chain. Scallops are the third most consumed shellfish in China. We therefore studied the accumulation, chemical forms, and distribution of semicarbazide in scallop tissues. Semicarbazide added to tank seawater resulted in its accumulation in both free and tissue-bound forms and the levels varied according to tissue and were present in all tissues examined. The levels were highest in viscera and the lowest in muscle. The levels of semicarbazide in the environment and in cultured shellfish should be monitored to ensure food quality and safety and human health.

Abstract

Semicarbazide is a newly recognized marine pollutant and has the potential to threaten marine shellfish, the ecological equilibrium and human health. In this study, we examined the accumulation, distribution, and chemical forms of semicarbazide in scallop tissues after exposure to 10, 100, and 1000 μg/L for 30 d at 10 °C. We found a positive correlation between semicarbazide residues in the scallops and the exposure concentration (p < 0.01). Semicarbazide existed primarily in free form in all tissues while bound semicarbazide ranged from 12.1 to 32.7% and was tissue-dependent. The time for semicarbazide to reach steady-state enrichment was 25 days and the highest levels were found in the disgestive gland, followed by gills while levels in gonads and mantle were similar and were lowest in adductor muscle. The bioconcentration factor (BCF) of semicarbazide at low exposure concentrations was higher than that at high exposure concentrations. These results indicated that the scallop can uptake semicarbazide from seawater and this affects the quality and safety of these types of products when used as a food source.

GV, Kumar A. Synthesis, molecular docking and DFT studies on biologically active 1,4-disubstituted-1,2,3-triazole-semicarbazone hybrid molecules

Biologically active semicarbazone-triazole hybrid molecules designed and synthesized from semicarbazone linked with a terminal alkyne and aromatic azidesviaCu(i)-catalyzed cycloaddition reaction. The synthesized compounds exhibited potent antibacterial activities against the tested bacterial strains. Computational results are in good agreement with thein vitroantimicrobial results.