Antimicrobial activity of different extracts of Centaurea depressa

Interest to natural medicines is increased for the sake of fewer side effects, microbial resistence and more compatibility to the human body. Centaurea depressa (commonly known "cornflower") belongs to compositeae family, which comprises more than 74 species in Iran. It has been claimed that it can be used in many cases, such as infections, cough, constipation, dermatitis, fever, jaundice, pain, water retention and cancer. Tannins, different salts, mucillage, cyanine are some of active compounds in this medicinal herb. In addition, lignanglycosides, sesquiterpenes, flavonoids and phytoecdysteroids have been found in different species of Centaurea. In this study Centaurea depressa was collected from Deilaman village in Gilan province in order to assay the antimicrobial activity, since it was used as an anticough and anticold remedy in those area. After collecting and drying the plants, extracts were made by perculation method in solvents with different polarity (hexane, chloroform and methanol). The agar diffusion method was used to assess the activity against five bacteria and one yeast: staphylococcus aureus, bacillus subtilis, escherchia coli, pseudomonas aeroginosa and candida albicans. The results, evaluated as the diameter of the inhibition zone of microbial growth, showed that methanolic extract was the most active extract against some gram-positive bacteria. Methanolic extract had more antimicrobial effect compared to nonpolar extracts. Therefore, the active compounds might have polar chemical structure that will be idetified by the research group.