General Description

Bronopol is an antimicrobial agent effective against bacteria, particularly Gram-negative strains, with low toxicity to mammals. It also exhibits antifungal properties, although it may be less effective against certain fungi compared to other compounds. A reliable detection method using LC-MS/MS has been developed for bronopol in aquaculture products, ensuring accurate results. This method involves extraction, cleanup, and chromatographic separation steps, offering simplicity, rapidity, and high sensitivity. The validation of this method confirms its potential for monitoring and preventing bronopol misuse in aquaculture, ensuring product quality and public health safety.

Figure 1. Bronopol

Antifungal Activities

Heisuke Oono and Kishio Hatai compared the antifungal activities of bronopol and 2-methyl-4-isothiazolin-3-one (MT) against members of the genus Saprolegnia in the family saprolegniaceae, which have the ability to infect fish. The minimum inhibitory concentration of bronopol was 100-200 mg/I but for MT it was 31 mg/I. Concerning fungicidal effects against the hyphae, treatment with bronopol at 100-200 mg/I for 30 min or treatment with MT at 25-50 mg/I for 30 min was effective in killing the vegetative stage of all fungal strains tested. Treatment with bronopol at 100 mg/I for 60 min or treatment with MT at 25-50 mg/I for 60 min was effective in killing the zoospores of all fungal strains tested. These results showed that MT was a more effective antifungal agent than bronopol against infectious members of the genus Saprolegnia.¹

Detection Method

Fish farming plays a vital role in providing food, nutrition, and employment globally. However, this industry faces security challenges, necessitating the use of fungicides and preservatives, such as bronopol, to increase product yields. Bronopol (2?bromo-2-nitropropan-1,3-diol; CAS:52–51–7) is widely used in various fields, including food production, cosmetics, and, more recently, aquaculture. Currently, there is a limited number of techniques available for detecting bronopol in aquaculture products. This is primarily due to bronopol's instability, susceptibility to degradation, and tendency to form precipitates that pose challenges in extraction from aquaculture products. 

Yongxin She's team present a comprehensive method for detecting bronopol content in aquaculture tissues using liquid chromatography-tandem mass spectrometry (LC?MS/MS). The methodology was optimized, involving extraction with Cu-Zn precipitant, cleanup using a small HLB column, separation on a T3 column, and gradient elution with water and acetonitrile mobile phases. The quantitative approach was employed without the use of an internal standard, following the external standard method. The spiked recoveries at 3 fortification levels (0.1, 0.2, and 1 mg/kg) ranged from 87.1 % to 108.1 % with relative standard deviations RSD ≤ 9.0 %. By applying this method to fresh fish, shrimp, crab, and shellfish samples from a local supermarket, no residues of bronopol were detected, ensuring the reliability of the results. The simplicity, rapidity, and high sensitivity of the method make it a suitable alternative to conventional techniques for bronopol detection. Moreover, the successful validation of the method's recovery and precision supports its potential application in monitoring and preventing the misuse of bronopol in aquaculture, thereby safeguarding aquaculture product quality and protecting public health.²

Reference

1. Oono H, Hatai K. Antifungal activities of bronopol and 2-methyl-4-isothiazolin-3-one (MT) against saprolegnia. Biocontrol Sci. 2007; 12(4): 145-148.

2. Wang M, Jia L, Jiao X, et al. A rapid method for detecting bronopol in fresh fish, shrimp, crab, and shellfish samples using liquid chromatography-tandem mass spectrometry. J Chromatogr A. 2023; 1710: 464429.