Plants That Have Antimicrobial Properties

Instructor: Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

In this lesson, we'll learn about natural antimicrobials from plants. We'll explain the function of antimicrobials and then look at some examples of plants with this property, including the popular spices garlic, tea tree, sage, and nutmeg.

What Are Antimicrobial Properties?

Have you ever had strep throat? Or maybe you've suffered from an ear or eye infection? Usually, when we have this type of ailment, we go to the doctor. They may then prescribe us an antibiotic. Antibiotics are drugs that kill bacteria, a type of microbe.

But, there are other types of microbes that can make us sick as well. Viruses, fungi, and parasites all can infect our bodies and cause illness. The collection of drugs that fights these pathogens are called antimicrobials. Antibiotics are one type of antimicrobial most of us are familiar with. But, not all antimicrobials come in pill form. Many plants have been used for thousands of years as medicine and still hold important antimicrobial properties today.


Around Halloween, many of us are fond of watching scary movies featuring ghouls and ghosts. If this is a tradition in your life, you probably know the myth of using garlic to ward off vampires. Vampires may not be real, but garlic, thanks to its antimicrobial properties, is able to ward off pathogens.

This is because garlic contains allicin, a molecule that has been shown to have antimicrobial properties against bacteria, fungi, viruses, and parasites. Scientists are especially interested in allicin because it has been shown to ward off bacteria that are resistant to an increasing number of antibiotics, such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). Allicin is also effective against Escherichia coli (E. coli), a common cause of food poisoning. Allicin has also been shown to kill Candida albicans, a yeast that causes opportunistic infections.

Tea Tree

Most of us have had an outbreak of acne at some point. If you go to the store in search of acne-busting face cleansers, you'll probably find some products with tea tree oil in it. The reason for this is that acne is actually caused by bacteria. Tea tree oil has antibacterial properties, making it an effective over-the-counter medication for this condition. Tea tree oil can also be found in soap and cleaning products.

Extracts from the tea tree plant are found in many antimicrobial products.
tea tree

Tea tree oil comes from the plant Melaleuca alternifolia, native to Australia. It has been used there for hundreds of years as a traditional medicine. The main active antimicrobial ingredient in tea tree oil is the aromatic hydrocarbon, terpinen-4-ol. Terpinen-4-ol is similar in structure to phenol, another commercial disinfectant that is toxic to cells.

Tea tree oil has been shown to have a variety of antibacterial effects, including inhibition of Escherichia coli, Streptococcus pyogenes, which causes strep throat, and Streptococcus pneumoniae, which causes pneumonia. However, scientists were excited to find that like garlic, tea tree oil also inhibits the growth of antibiotic-resistant bacteria like MRSA.


Believers in the energetic fields of the human body often use sage as a way to cleanse a space of negative energy. Sage doesn't just energetically cleanse a space; it can also physically cleanse it of unwanted microbes.

Unlike garlic or tea tree oil, there are dozens of active components in sage that contribute to its medicinal properties. However, scientists have found that three, in particular, cause the most biological activity; camphor, 1,8-cineole, alpha-thujone, and beta-thujone.

Sage contains many active antimicrobial chemicals in its extracts.

If you've ever struggled with cavities, sage might be for you. Sage has been shown to kill several species of bacteria responsible for dental plaque, such as Streptococcus mutans. This offers an alternative to chemical-based mouthwashes used in dental hygiene.

Sage extracts aren't just for dental problems though. Sage has also been shown to inhibit the growth of bacteria that are involved in serious gastrointestinal infections such as Escherichia coli and Salmonella typhi, the cause of typhoid fever.

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