## 3 Biological Activities
### Antibacterial Activity
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Microorganism** & **Dose (MIC)** & **Effect** & **Ref.** \\ \hline Bacteria & & \\ _V. parahaemolyticus_ & 0.125 mg/mL & Inhibited bacterial growth, causing damage to bacterial membrane and cell wall. & [47] \\ _S. aureus DMST 4745_ & 0.62–1.25 \(\mu\)L/mL & \\ _S. aureus_ & 0.62–1.25 \(\mu\)L/mL & \\ _S. agalactica_ & 0.31–0.62 \(\mu\)L/mL & Citral possessed bacteriostatic and bactericidal actions at different concentrations. & [48] \\ _B. cereus_ & 0.15 \(\mu\)L/mL & \\ _E. coli_ & 1.25–2.5 \(\mu\)L/mL & \\ _E. coli_ MG1655 & 300 \(\mu\)L/L & It inactivated at least 2.5 log\({}_{10}\) cycles of exponentially growing cells in 3 h under aerobic conditions. & [49] \\ _L. monocytogenes_ & 200 \(\mu\)L/mL & Growth inhibition. & [50] \\ _S. aureus_ & 500 \(\mu\)L/mL & \\ _E. coli_ & 500 \(\mu\)L/mL & \\ _L. monocytogenes_ & 0.125 mL/mL & Microbial growth of both _Listeria_ species was reduced by almost 2 log\({}_{10}\) CFU/mL. & [51] \\ _L. innocua_ & 0.125 mL/mL & Citral in the culture medium of both bacteria provided a reduction of bactircain from 32 ug/mL to 4 ug/mL, and the colistin changed from 96 and 128 ug/mL for _L. monocytogenes_ and _L. innocua_, respectively, to 16 ug/mL, for both species. Citral at subinhibitory concentrations (1, 2, and 3 mM) could induce bacterial adaptation and acquire tolerance to inactivation processes. & [52] \\ \hline Fungi & & & \\ _B. dothidea_ & 0.2 \(\mu\)L/mL & At 0.4 \(\mu\)L/mL, citral entirely inhibited the growth of all the tested fungi. When concentration reached 0.2 \(\mu\)L/mL, citral inhibited the growth of _B. dothidea_ best, followed by _P. macrospore_ and _B. cinerea_. & [54] \\ _C. sakazakii_ & 0.8 mg/mL & Growth inhibition and cell damage. & [55] \\ _3600 \(\mu\)M_ & Concentrations below 225 \(\mu\)M (1/16 MIC) exhibited no inhibition against _C. sakazakii_ ATCC 29544. & [55] \\ _Penicillium roqueforti_ & 0.17 mg/mL & Citral combination with eugenol damaged the cell membrane, caused a collapse of mitochondria, and inhibited energy production. & [16] \\ _Penicillium digitatum_ & 2.0 or 4.0 \(\mu\)L/mL & Citral altered the mitochondrial morphology, led to the leakage of ATP, and showed an inhibition of the TCA pathway of _P. digitatum_ cells. & [56] \\ _S. cerevisiae_ & 2.0 mM & MIC: Results showed that yeast cells treated with 2 mM citral reached a 95\% reduction in CFU/mL. & [57] \\ _Zygosaccharomyces roucxii._ & 0.188 \(\mu\)L/mL & The minimum fungicidal concentration was 0.375 \(\mu\)L/mL. & [58] \\ _Candida albicans_ & 64 ug/mL & MIC and the MFC of citral required only 4 h of exposure to effectively inhibit 99.9\% of the inoculum. & [59] \\ _Aspegillus niger_ & 0.23 mg/mL & The combination of citral and eugenol had a synergistic inhibitory effect on _A. niger_. & [16] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Antibacterial and antifungal activities of citral. could potentially be used to control _C. sakazakii_ in food. However, the way it works in food systems, where many other components can interfere with its effectiveness, needs to be tested in future research before its actual application. The potential of citral on the growth and virulence properties of _Vibrio parahaemolyticus_ has been evaluated. Citral showed good antibacterial activity, and the MIC was determined to be 0.125 mg/mL. Citral caused damage to the wall and membrane of bacterial cells based on the morphology observed by electron microscopy. Treatment with citral at sub-inhibitory concentrations caused a decrease in biofilm formation, motility, extracellular production of polysaccharides, and the levels of transcription of genes involved in the production of hemolysis, type III, and VI secretion systems in _V. parahaemolyticus_ RIMD2210633. Furthermore, citral inhibited the quorum-sensing genes and the ToxRS system in a concentration-dependent manner [47]. The results strongly suggest that citral could be a promising alternative therapy for combating infections linked to _V. parahaemolyticus_.