# In vitro and in vivo antimicrobial activity of protoberberine alkaloids as novel therapeutic candidates against Mycoplasma hyopneumoniae

## TL;DR

This study shows that natural compounds called protoberberine alkaloids can effectively fight a harmful pig lung infection caused by Mycoplasma hyopneumoniae.

## Contribution

The study identifies protoberberine alkaloids as novel, safe, and effective natural alternatives to antibiotics for treating M. hyopneumoniae infections in pigs.

## Key findings

- Protoberberine alkaloids inhibited M. hyopneumoniae with minimum inhibitory concentrations between 8 and 32 µg/mL.
- Jatrorrhizine reduced clinical symptoms and lung damage in infected pigs as effectively as florfenicol.
- The compounds showed low cytotoxicity and strong anti-inflammatory effects in infected cells.

## Abstract

Mycoplasma hyopneumoniae (M. hyopneumoniae, Mhp), the primary causative agent of swine enzootic pneumonia, poses significant threats to the pork industry, challenging food safety and sustainable development of the livestock industry. Here, four protoberberine alkaloids—epiberberine, jatrorrhizine, berberine, and coptisine—were identified by screening multiple natural compounds, and their anti-Mhp activity was evaluated. All alkaloids exhibited potent inhibitory effects against the virulent Mhp strain ES-2, with minimum inhibitory concentrations from 8 to 32 µg/mL. Their bactericidal activities were time- and concentration-dependent. At the cellular level, all protoberberine alkaloids significantly enhanced infected cell viability, suppressed pro-inflammatory cytokine expression (TNF-α, IL-6, and IL-1β), and exhibited low cytotoxicity toward host cells. In a Chang Da binary cross-breeding pig infection model, jatrorrhizine markedly alleviated clinical symptoms, reduced pulmonary pathogen loads, and mitigated histopathological damage in lung tissues, with therapeutic efficacy comparable to that of florfenicol. Our findings demonstrated that protoberberine alkaloids possessed potent anti-Mhp activity, high safety profiles, and promising therapeutic potential.

Swine enzootic pneumonia, caused by Mycoplasma hyopneumoniae (M. hyopneumoniae), remains one of the most economically devastating respiratory diseases in the global swine industry. The emergence of antibiotic resistance in livestock highlights the urgent need for effective, safe, and sustainable alternatives. This study demonstrates that naturally derived protoberberine alkaloids exhibit potent antibacterial activity against M. hyopneumoniae while maintaining low host cytotoxicity and strong anti-inflammatory effects. Among them, jatrorrhizine showed remarkable therapeutic efficacy in infected pigs, comparable with that of florfenicol. These findings provide a scientific basis for developing protoberberine alkaloids as promising natural alternatives to conventional antibiotics for controlling M. hyopneumoniae infections, thereby contributing to improved animal health, reduced antimicrobial resistance, and sustainable swine production.