## 4 Discussion  
In general, raw propolisis is not used in the preparation of food or medicine due to its composition. Extracts are its most common form, and it is important to consider that the performance of the extracts is variable due to different factors, such as the extraction method (maceration, Soxhlet, ultrasound-assisted extraction, microwave-assisted extraction, supercritical fluids with CO\({}_{2}\) and high pressure), the nature of the solvent (according to its polarity; low, medium or high), ratio or proportion of solvent and time and tempera  
Figure 2: Inhibitory activity of propolisis extracts against different microbial strains. (**A**) _Staphylococcus aureus_ (ATCC 13709), (**B**) _Candida albicans_ (ATCC 1023), (**C**) _Escherichia coli_ (ATCC 25922) and (**D**) _Salmondella typhimurium_ (ATCC 43971). ture of extraction [4; 15]. Our extracts presented a yield of 63.8 to 71.5%, being higher than the 2.57 to 22.67% [25] and 18.2% [26] of various propolis simples. According to the Official Mexican Standard, propolis marketed in Mexico must have a minimum of 5000 mg EGA/100 g of phenolic compounds [3]. The propolis analysed had a total phenol content of 30,824.9 to 34,406.6 mg EGA/100 g, thus complying with Mexican regulations. In addition, these results are higher than those reported in ethanolic extracts of propolis from China (8934.3 to 20,178.6 mg EGA/100 g). These extracts were obtained with ultrasounds, and the difference in the content of total phenols could be related to the type of vegetation from which the bees collected the propolis and the collection season, as well as various environmental factors [27; 28]. Ethanolic extracts (70%) of propolis from Turkey have a very variable total phenol content, ranging from 2748 to 19,970 mg EGA/100 g. The authors mention that this variability is associated with the geographical origin of the propolis. In addition, these values are lower than ours [29]. On the other hand, aqueous extracts of propolis from Algeria have a total phenol content of 9688.3 to 45,883.3 mg EGA/100 g, the variation was mainly due to the place of origin of the propolis [30]. On the other hand, there are various methods for the purification of extracts, which can influence the content of bioactive compounds. In the elaboration of propolis extracts from Greece, four purification methods were used, obtaining a total phenol content of 11,385 to 29,811 mg EGA/100 g, centrifugation being the most effective method [31]. The total phenolic content in ethanolic extracts of propolis from Turkey was 25,000 mg EGA/100 g. However, at the end of in vitro digestion only 8.9% were bioavailable. It should be noted that in vitro digestion was performed in crude propolis [29], thus the low bioavailability of phenols could be due to acid conditions and possible isomerization reactions of the phenolic compounds during the digestion process [32]. The bioavailability of our extracts at the end of digestion was 20.88 to 26.62%. The range of total flavonoids in our extracts was from 2859 to 19,523 mg EQ/100 g of propolis. These results are higher than those proposed by the Mexican regulations (min. 500 mg EQ/100 g). Various investigations report a total flavonoid content of 3823 to 4745 mg EQ/100 g [31]; 304.7 to 527.3 mg EQ/100 g [30]; 16,622 to 51,977 mg EQ/100 g [27]; 1100 to 15,000 mg EQ/100 g [7]; 4946.5 mg EQ/100 g [33]; and 55,758 mg EQ/100 g [26]. As we can see, the flavonoids' content is highly variable; therefore, biological activity could vary. As mentioned above, the composition of phenolic compounds (flavonoids) depends on factors, such as floral and geographical origin. However, for the biological properties of the extracts to be preserved, it is important to assess the bioavailability at the end of the digestion. The bioavailability of total flavonoids from our extracts at the end of in vitro digestion ranged from 0.68 to 9.36%. Therefore, it is important to look for alternatives for the protection of bioactive compounds during gastrointestinal conditions.