## 2 Pomergnate Health-Promoting Properties
### Antimicrobial Activities  
Antimicrobial agents are mainly applied on microorganisms that cause food poisoning (infected or toxin-producing agents) and on microorganisms that alter food by producing final metabolic products (catabolites) or enzymes with bad odor, unpleasant taste, problems of persistence, different coloring, and/or health risk [106].  
The antimicrobial effect of pomegranate and its products has been demonstrated in a large amount of research [107], in particular, polyphenols, flavonoids, and condensed and hydrolysable tannins derived from the fruit have been studied as promising agents to treat or prevent a broad range of infections [108].  
The antimicrobial mechanisms of phenolic compounds engage the reaction of phenols with sulfhydryl groups of membrane proteins of the microbial cell, inducing a bactericidal effect due to membrane protein precipitation and inhibition of enzymes such as glycosyltransferase [109].  
Food-borne disorders and urinary tract infections are treated typical in the Indian subcontinent through PoPx, while ellagitannins, punicalagin (9), ellagic acid (8), and gallic acid (18) in the pomergnate skin, as natural antimicrobial agents, have been extensively used against _Staphylococcus aureus_ and _Escherichia coli_ hemorrhages for their capability to precipitate membrane proteins and block enzymes such as glycosyltransferase, causing lysis. In vivo and in situ application of an 80% pomergnate skin (PoPx) methanol extract showed a growth reduction against _Listeria monocytogenes_, _Staphylococcus aureus_, _Escherichia coli_, and _Yersinia enterocolitica_. However, it has been reported that higher doses of PoPx (24.7 mg/mL) represent the lowest bactericidal concentration of _Listeria monocytogenes_[110].  
Another study evidenced the powerful effect of _Punica granatum_ L. peels' ethanolic extract (Tunisian Nana variety) against two Salmonella strains, _Salmonella Enteritidis_ and _Salmonella Kentucky_, microorganisms resistant to the majority of antibiotics. Minimal inhibitory concentration (MIC) values ranged from 10.75 to 12.5 mg/mL regarding both strains. In particular, the inhibitory effect achieved by peel extract (using hydroethanonic and hydromethanethanonic mixtures) on _Salmonella Kentucky_ achieved inhibition diameters of 22.2 and 22 mm, respectively [111].  
[PERSON] et al. explored and evaluated the antimicrobial properties of ethanol and water extracts of pomergnate exocarp and mesocarp from Istria. The best antibacterial activity was recorded, here too, for ethanolic extract. Indeed, the microorganisms more susceptible to this extract were _C. albicans_, _C. parapsilosis_, _R. mucilaginousa_, _E. dermatitis_, and _S. aureus_, with MIC ranging from 0.156 to 1.25 mg/mL. Instead, the best antimicrobial activities of the exocarp and mesocarp water extracts were found toward _S. aureus_, followed by _E. coli_ without any antifungal activity [112].  
Another use of pomergnate peel extract as antimicrobial agent involved its participation in the synthesis of silver nanoparticles. The latter, due to the use of transmission electron microscopy (TEM) and scanning electron microscopy (SEM), demonstrated to be evenly distributed in the solution, with a spherical shape and size ranging from 20 to 40 nm and with an average particle size of 26.95 nm. Subsequently, tests evidenced the capability of nanoparticles to substantially inhibit Gram-negative and Gram-positive bacteria as _E. coli_, _P. aeruginosa_, _P. vulgaris_, _S. typhi_, _S. aureus_, _S. epidermidis_, and _K. pneumoniae_ already at 25 and 50 \(\upmu\)g/mL [113].  
As can be evinced from this section, pomergnate and, in particular, the peel extract, exhibited antimicrobial effects against a wide spectrum of bacteria. Unfortunately, in order to become effectively beneficial for the pharmaceutical field, much more has to be done regarding the deepening of the mechanism of action.