## 3 Antimicrobial Activities of p-C
### Biosynthesis and Antibacterial Effects from Plants  
p-C is the main compound in the genera Thymus and Origanum, and is a precursor to essential oils and carvacrol, which has antimicrobial properties. Although p-C is weakly antimicrobial on its own, it plays an important role in the overall antimicrobial composition and facilitates the synergistic effects of carvacrol and thymol [57; 58; 59]. p-C increases antimicrobial activity through intracellular penetration, integrates bacteria, and aids in the transport of carvacrol across lipid layers and cytoplasmic membranes. p-C is also hydrophobic, which allows for the easy swelling of the cytoplasmic membrane and has a high solubility in water [60; 61; 62; 63]. The antimicrobial properties of p-C have also been demonstrated in experiments on Thymus species. The different biological activities of Thymus bulgaris (TVEO) and Thymus serpyllum (TSEO) are attributed to their main component, p-C. TSEO showed a 2,2-diphenyl-1-picrylhydrazyl (DPPH) value of 4.88 \(\upmu\)L/mL and a ferric-reducing antioxidant power (FRAP) of 701.25 \(\upmu\)mol FRAP/g, and in addition to its bacterial activity, it caused apoptosis via caspase-3. TVEO showed a DPPH value of 4.49 \(\upmu\)L/mL and FRAP of 1130.27 \(\upmu\)mol FRAP/g and was found to induce the apoptosis of cervical adenocarcinoma Henrietta Lacks (HeLa) cells through the activation of caspase-3 and caspase-8. In particular, HeLa cells decrease the expression levels of matrix metalloproteinase-2 (MMP2) and increase the levels of microRNA (miRR)-16 and miR-34a, which may have potential tumor suppressive effects in the future [64]. The antimicrobial effect of p-C was demonstrated in a mixture of the natural compounds carvacrol, thymol, and p-C as a potential food preservative. It inhibited yeast growth at a concentration of 1 mmol/L for at least 21 days. p-C in particular showed effective antimicrobial activity with an extension to 45 days [65]. The antimicrobial role of p-C is also applied in food by its bactericidal effect. This is because p-C (33.14%), mainly contained in _Satureja horvatii_, improved the color and flavor of meat after 4 days of storage and inhibited the development of _Listeria monocytogenes_. This in turn shows that it can be used as a useful source of food spoilage microbial inhibitors and natural antioxidants [66]. Apple juice contaminated with _Escherichia coli_ O157:H7 can lead to food poisoning outbreaks, serious illness, and death. In response, the addition of p-C's natural antimicrobial properties is being discussed as a processing method to prevent vitamin loss and preserve flavor. As a phenolic substance, p-C, together with carvacrol, is a component derived from essential oils of herbs and spices and may provide a new route for potential shelf-life extension [67]. It was also found that p-C, as a precursor to carbacrol, has similar antimicrobial activity to carbacrol against foodborne pathogens, but carbacrol alone is more effective against non-vibrio cholera [68; 69; 70]. Although p-C alone does not show a good inhibition of _Vibrio cholerae_, synergistic antimicrobial activity with carbacrol has been demonstrated. This demonstrates the potential of combining p-C and carbacrol [71]. Essential oils obtained from cumin (_Cuminum cyminum_) and adjuvant (_Tachyspermum ammi_) also showed antimicrobial and antioxidant activities of the main component p-C. Compared to standard antibiotics, it was found that cumin had a stronger antibacterial effect than chloramphenicol, cumin had weak antioxidant activity (12.36%), and azowan had strong antioxidant activity (71.68%) in scavenging DPPH radicals. Furthermore, azowan had a stronger antioxidant effectthan ascorbic acid (20.24%), indicating that it has significant potential for food pathogen control [72].