LAVINIA MOLERIU, CALIN JIANU, GABRIEL BUJANCA, GABRIELA DOROS, CORINA MISCA, OVIDIU CALIN ILIE, RADU DUMITRU MOLERIU, ADRIAN COSMIN ILIE ESSENTIAL OIL OF HYPERICUM PERFORATUM THE CHEMICAL COMPOSITION AND ANTIMICROBIAL ACTIVITY The chemical composition and antimicrobial activity of the essential oil isolated by steam distillation from Hypericum perforatum L. (St John’s wort) growing wild in western Romania have been studied. The extraction yield was 0.41% (v/w) based on the dry plant material. The essential oil was analyzed by GC–MS, and a total of twenty-two components were identified. The major components were alpha-pinene (30.92%), beta-pinene (18.32%) and caryophyllene (15.26%). The antimicrobial activity of the H. perforatum essential oil was screened using the disk diffusion method against 7 common food-related bacteria and fungus. The analyzed EO possesses strong antimicrobial activity. Klebsiella pneumoniae and Pseudomonas aeruginosa were the most resistant species. The analyzed oil can represent an inexpensive natural source of antiseptic compounds, an alternative to synthetic preservatives.