# Propolis as Natural Product in the Oral Cavity Bacterial Infections Treatment: A Systematic Review
## 5 Discussion  
Taking into account the MIC and MBC values as well as the inhibition zones for different microorganisms, which could be found in the reviewed papers, we prepared Figure 3a-c, which shows mean values of MIC and MBC in \(\mathrm{\SIUnitSymbolMicro g}\)/mL as well as inhibition zone in mm.  
Figure 3: Antibacterial activity of propolisis: (**a**) The mean MIC values \(\pm\)SEM expressed in \(\mathrm{\SIUnitSymbolMicro g}\)/mL for the bacterial strains causing oral cavity infections [7; 14; 15; 19; 21; 34; 36; 59; 60; 63; 64; 65; 66; 71; 72; 75; 77; 82; 84; 85; 87; 89; 90; 91; 92; 93; 94; 97; 98; 99; 100; (**b**) The mean MBC values \(\pm\)SEM expressed in \(\mathrm{\SIUnitSymbolMicro g}\)/mL for the bacterial strains causing oral cavity infections [14; 15; 19; 21; 34; 59; 60; 63; 66; 68; 75; 77; 82; 84; 85; 91; 98; 100; (**c**) The mean inhibition zone \(\pm\)SEM expressed in mm for the bacterial strains causing oral cavity infections [6; 15; 31; 63; 64; 66; 67; 73; 81; 83; 86; 93; 95; 96].  
Based on the average values of MIC (\(\upmu\)g/mL) (Figure 3a), it can be concluded that the lowest MIC values for propolisis were recorded in _Eikenella spp._, _Peptostreptococcus spp._, and _Veionella spp._ Propolis exhibited the highest antimicrobial activity against the same strains. Interestingly, various types of propolisis did not affect _Actinomyces spp._, _Lactobacillus spp._, and _Streptococcus spp._ (average MIC: 0.50, 9.45, and 0.81 mg/mL, respectively). For MBC (in \(\upmu\)g/mL) (Figure 3b), the highest antimicrobial activity was recorded in case of _Peptostreptococcus spp._, and _Veionella spp._ It is noteworthy that _Actinomyces spp._, _Lactobacillus spp._, and _Streptococcus spp._ (average MBC: 0.84, 8.24, and 2.71 mg/mL, respectively) were also the most resistant to different types of propolisis. In case of the inhibition zone (Figure 3c), the most sensitive to propolisis extract are _Porphyromonas spp._, _Aggregatibacter spp._, _Streptococcus spp._, _Actinomyces spp._, and _Fusobacterium spp._ with inhibition zones of 2.20, 1.46, 1.02, 0.90, and 0.69 cm, respectively. The most resistant is _Lactobacillus spp._ with an inhibition zone of 0.54 cm. Moreover, the presented results confirm that propolisis may be employed to treat bacterial infections of the oral cavity, such as periodontitis, tooth decay, supragingival plaque, subgingival plaque, gingivitis, RAS, and pharyngitis.  
The observed high values of SEM In MIC and MBC recorded for the same genus of bacteria may result from the fact that the bee product effect persists over varied amounts of time in the tested microorganisms. Moreover, propolisis may contain various active substances at different concentrations. The sensitivity of the tested bacterial strains differed, and researchers used various methods to estimate their bioactivity [113]. To achieve the standardization of bee products, a lot of aspects must be taken into consideration [114]:  
* Composition: depends on the geographic specificity of the region, ecoregions, flora, and on when and how bee products were collected;
* The content of the nutritional and active ingredients;
* The storage condition: raw propolisis at 4\({}^{\circ}\)C or -20\({}^{\circ}\)C in dark for 30 days;
* Different assessment methods, e.g., GC-MS to analyze the chemical composition of raw propolisis, HPLC in gradient mode coupled with PAD to analyze the most appropriate ingredients of propolisis, headspace solid-phase microextraction (HS-SPME) techniques to establish the fingerprint of raw propolisis samples from various regions, and electrochemical techniques to determine the antioxidant properties of propolisis samples at an early stage.  
The review by [PERSON] et al. [114] discusses thoroughly the above-listed issues.