Oregano and marjoram are closely related spices of the mint family. Oregano and marjoram are small shrubs with 1/4-inch-wide oval leaves. Their flavor is earthy and aromatic. Their tastes are quite similar, thought oregano is a bit stronger and marjoram as sweeter.
Oregano's botanical name is Oreganum vulgare, and it is called wild marjoram in many parts of Europe
The volatile oil of oregano contains thymol and carvacrol, two powerful antimicrobial agents. A clinical study compared oregano to tinidazole, a commonly used prescription drug to treat infection by amoeba Giardia lamblia. These researchers found oregano to be more effective against Giardia than prescription drugs. Thymol and carvacrol have also been shown to supress the growth of bacteria, including Pseudomonas aeruginosa and Staphylococcus aureus, two bacteria that are often the cause of impetigo (an infection of the skin).
Oregano also has tremendous antioxidant activity. In one study conducted by the USDA, oregano scored the highest in antioxidant activity of any herb or food tested, ranking even higher in antioxidant activity than fruits and vegetables known to be high in antioxidants. Oregano had fourty-two times as much antioxidant activity as apples, thirty times as much as potatoes, twelve times as much as oranges, and four times as much as blueberries. The active component was rosmarinic acid, which, as its name suggests, is also found in rosemary as well as in mints.
How to select and store -Whenever possible, choose fresh oregano and marjoram over dried, since they are superior in flavor and health benefits. The leaves of fresh oregano and marjoram should be vibrant green in color and free from dark spots or yellowing. Fresh oregano and marjoram should be wrapped in damp paper towels and stored in the refrigerator, where they will keep for up to seven days. They may be also frozen, either whole or chopped, in airtight containers. They will keep for three months in the freezer. Alternatively, you can freeze the oregano in ice cube trays covered with either water or stock that can be added when preparing soups or stews.
If fresh oregano and marjoram are not available, dried can be used. Just as with other herbs, try to buy that which has been organically grown, since organically grown herbs are much less likely to have been irradiated. They should be kept in tightly sealed glass containers where they will remain fresh for about six months.
Cooking tips - Oregano and marjoram, in either their fresh or dried form, are best added toward the end of the cooking process, since heat can easily destroy their aromatic oils and delicate flavors.
No significant safety concerns are associated with consumption of oregano or marjoram. There are also some reports regarding the antimutagenic (preventing damage to DNA) and anticarcinogenic effect of oregano. Aristolochic acid I and II obtained from oregano plant were confirmed to possess activity against cancer. Some researchers suggest that oregano may be used as alternative for the potential treatment and/or prevention of certain chronic ailments, like cancer.