# Plant-Derived Phytobiotics as Emerging Alternatives to Antibiotics Against Foodborne Pathogens
### Phenolic Compounds
#### 2.1.2 Polyphenols  
These are natural plant compounds that contain two or more hydroxyl groups attached to aromatic rings. Polyphenols can be further subdivided into four main groups: flavonoids, stilbenes, tannins, and lignans [14]. Polyphenols play an important biological role in  
Figure 1: The major groups of phenolic compounds. plants, exhibiting a broad spectrum of protective, structural, regulatory, and signaling functions. In their capacity as powerful antioxidants, they participate in neutralizing reactive oxygen species formed under abiotic stress conditions, such as UV radiation, temperature fluctuations, drought, or the presence of heavy metals. Simultaneously, they protect plants from biotic stress by acting as antimicrobial compounds against bacteria, fungi, and viruses and as repellents against insects and herbivores. Polyphenols affect the structural integrity of plants by participating in the construction of cell walls and regulate key physiological processes such as seed germination and plant growth and development, enabling them to adapt to changing environmental conditions. They also play an important role in ecological interactions--attracting pollinators and seed dispersers by imparting color to flowers and fruits, while repelling herbivores through their bitter taste and toxicity. Some of them exhibit allebotathic effects, inhibiting the growth of competing plant species. Moreover, polyphenols participate in the transmission of cellular signals and activation of defense mechanisms, and their biosynthesis is an adaptive response of plants to changing environmental conditions, promoting the storage of carbon compounds during periods of limited nitrogen availability or slowed growth. Polyphenols are attributed with numerous health-promoting properties, primarily due to their potent antioxidant activity. Polyphenols exhibit a broad spectrum of biological activities. They protect cells from oxidative stress, modulate inflammatory processes, support cardiovascular function, and inhibit the growth of cancer cells. They interact with the intestinal microbiome, supporting its balance, and exhibit antimicrobial activity against bacteria, fungi, and viruses, helping to strengthen the body's defense mechanisms [3; 21; 22; 23; 24; 25]. The largest and most structurally diverse group of phenolic compounds comprises flavonoids. These encompass subclasses such as flavonoids (e.g., quercetin, kaempfer, myricetin), flavones (e.g., apigenin, luteolin, chrysin), flavanones (e.g., naringin, hesperetin), flavanols (e.g., catechin, epicatechin, epigallocatedchin), isoflavenes (e.g., genistein, daidzein), and anthocyanins (e.g., paonidin, delphinidin, cyanidin). Flavonoids, commonly found in various plant organs, play an important role in imparting color and fragrance to flowers and fruits, promoting pollination and seed dispersal. They participate in plant defense mechanisms against biotic and abiotic stresses, acting as natural UV filters, signaling molecules, phytoalexins, detoxifying, and antimicrobial compounds. They also support resistance to drought, frost, and heat stress [26]. Stilbenes (1,2-diphenylethylene) are characterized by a C6-C2-C6 backbone. These compounds are produced by plants as secondary metabolites that play a protective role under stress conditions and against pathogens, bacterial and fungal growth. The most well-known representative of this group is resveratrol, particularly recognized for its antioxidant and anti-inflammatory properties. It occurs naturally, among others, in grapes, red wine, peanuts, blueberries, cranberries, chocolate, and tomatoes. Other representatives of this group include gnetol, pterostilbene, piceatannol, polydatin, oxyresveratrol, isorhapontin, astrringin, and amurensin H [27]. Lignans are natural compounds belonging to the polyphenol class, found mainly in seeds, grains, fruits, and vegetables, with flaxseed and sesame being particularly rich sources.