# Biological Activities of Selected Medicinal and Edible Plants Aqueous Infusions
## 3 Results and Discussion
### Antibacterial and Antidiabetic Activities of Aqueous Herbal infusions  
The antibacterial activity of selected aqueous plant infusions was tested against _Escherichia coli_ ATCC 25922 and _Staphylococcus aureus_ ATCC 25923 as representatives of gram-negative and gram-positive bacteria using the microdilution method. The antibacterial activity of the different concentrations of the infusions (4--0.0078 mg/mL) showed no inhibitory effect against _Escherichia coli_ ATCC 25922 and _Staphylococcus aureus_ ATCC 25923. However, many authors have found the antibacterial activity of various extracts of selected medicinal and edible plants against different bacterial strains. Most studies are based on the antibacterial activity of ethanolic and methanolic extracts, not on the aqueous extracts. The available results vary depending on the type of extract and bacterial strain and it is possible to draw completely opposite conclusions. The lack of inhibitory activity of four different solvent extracts of _G. macrorrhizum_ and _V. thapsus_ against _E. coli_ is also reported by other authors [8; 38; 42]. [PERSON] and [PERSON] [43] have demonstrated the antibacterial activity of the aqueous extract of _V. thapsus_ only against _K. penumonia_ and _S. aureus_, while _E. coli_ did not show sensitivity to the the samples tested. The antimicrobial activity against _S. aureus_ was found for _G. macrorrhizum_ (ethanolic extract), _V. thapsus_ (methanolic and ethanolic extract), _O. spinosa_ (methanolic extract), _A. millelotium_ (hexane, petroleum ether, methanol) [16; 39; 44; 45]. The use of medicinal plants could play an important role in combating hyperglycemia by inhibiting digestive enzymes--a-amylase and \(\alpha\)-glucosidase. Their inhibition delays the breakdown of carbohydrates in the small intestine and decreases postprandial blood glucose level, which is important in type 2 diabetes. The results of inhibitory activity of \(\alpha\)-amylase and \(\alpha\)-glucosidase by aqueous infusions of selected plants are shown in Table 3. The highest inhibitory activity of both digestive enzymes was achieved by _G. macrorrhizum_ whose effect on \(\alpha\)-glucosidase inhibition is even more effective than that of acarbose, a widely used drug for the treatment of type 2 diabetes. _O. spinosa_ showed excellent inhibitory activity of \(\alpha\)-glucosidase and good inhibitory activity of \(\alpha\)-amylase. _V. thapsus_ and _P. aviculare_ showed moderate inhibitory activity of \(\alpha\)-glucosidase. _A. millelotium_ showed no inhibitory effect of the two digestive enzymes. The anti-hyperglycemic activity of extracts of selected plants (mostly ethanolic and methanolic) by inhibiting \(\alpha\)-glucosidase and \(\alpha\)-amylase has been reported by many authors [16; 30; 32; 44; 46; 47; 48]. Numerous studies have reported the inhibitory potential of phenolic compounds against \(\alpha\)-amylase and \(\alpha\)-glucosidase, explaining that the structure of polyphenol affect their ability to interact with the enzyme and the presence of methoxyl groups on benzoic acid derivatives [49]. This is consistent with our results for _G. macrorrhizum_, which contains high levels of syringic acid and also high level of procyanidins (Table 1).