Microbial infections affect both the human population and animals. The appearance of more and more microbial strains resistant to classical treatments led to the need to develop new treatments.Alliumplants are known for their antimicrobial properties due to their high content of thiosulfinates, especially allicin, polyphenols or flavonoids. The hydroalcoholic extracts of sixAlliumspecies obtained by cold percolation were analyzed regarding their phytochemical compounds and antimicrobial activity. Among the six extracts,Allium sativumL. andAllium ursinumL. have similar contents of thiosulfinates (approx. 300 μg allicin equivalents/g), and the contents of polyphenols and flavonoids were different between the tested species. The HPLC-DAD method was used to detail the phytochemical composition of species rich in thiosulfinates.A. sativumis richer in allicin (280 μg/g) thanA. ursinum(130 μg/g). The antimicrobial activity ofA. sativumandA. ursinumextracts againstEscherichia coli,Staphylococcus aureus,Candida albicansandCandida parapsilosiscan be correlated with the presence of large amounts of thiosulfinates. Both extracts have shown results againstCandidaspecies (inhibition zones of 20–35 mm) and against Gram-positive bacteria,Staphylococcus aureus(inhibition zones of 15–25 mm). These results demonstrate the antimicrobial effect of the extracts and suggest their use as an adjuvant treatment for microbial infections.