In an effort to minimize the undesirable effects of the synthetic food preservatives in human health, food industries and scientists have recently turned the interest to new preservatives. Aromatic plants are well known for their antioxidant and antimicrobial properties that prevent food degradation and alteration, as they are rich in phenolic substances, usually referred as polyphenols, which are ubiquitous components of plants and herbs. The antioxidant capacity was determined, in dried plants and in their methanol extracts and essential oils, with the Rancimat test using sunflower oil as substrate. The method used is the official method of AOCS, Cd 12B-92 for lipid oxidation determination. All grounded plants, essential oils and their extracts showed antioxidant capacity. The antioxidant capacity was expressed as PF values. The outcome of the Rancimat test supports the claim that aromatic plants are good sources of natural antioxidants such as phenolic compounds. When ground material was added to sunflower oil, protection factors were slightly higher compared to the addition of methanol extracts and essential oils.