15 Amazing Natural Antibiotics - Scientific Research findings


Antibiotics were first discovered when Alexander Fleming noticed mould (Penicillium notatum) inhibiting the growth of bacteria. Pharmaceutical antibiotics were later developed but most have harmful side effects such as vomiting, diarrhoea, allergic reactions, and rashes. Infectious illnesses caused by bacteria, fungi, or viruses are extremely common. The over prescription and misuse of pharmaceutical antibiotics have led to many bacteria developing antibiotic resistance. Fortunately, there are many naturally occurring antibiotics with few side effects.

Many spices and herbs, such as garlic, oregano, thyme, and turmeric exhibit impressive antibacterial, antifungal, and antiviral properties and can be used as natural alternatives.

1) Garlic

Garlic has been widely used throughout history for the treatment and prevention of diseases. Recent studies have evaluated the many benefits of garlic, including antibacterial, antifungal, and antiviral activity. Allicin is the main active compound in garlic, responsible for most of the antimicrobial activity. It is effective against many strains of bacteria, including multidrug resistance strains. Allicin kills bacteria by blocking enzymes important for energy production and cell structure. Allicin prevents bacterial and fungal growth by blocking the formation of biofilms. Biofilm infections, such as in pneumonia in cystic fibrosis patients and persistent wounds, are chronic infections that affect millions of people a year.

Garlic extracts might be helpful in treating swollen gums and preventing cavities since it kills oral pathogens such as Porphyromonas gingivalis, Prevotella intermedia, and Aggregatibacter actinomycetemcomitans.

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Antifungal Activity - Allicin in garlic extracts blocked the germination of spores and fungal growth (Candida albicans, Cryptococcus, Aspergillus, and Saccharomyces cerevisiae). Ajoene, another component found in garlic, killed the fungus which causes athlete’s foot (tinea pedis) (0.4% cream, 14-day trial of 34 patients)

Antiviral Activity - Garlic extract is also effective against the influenza virus and herpes viruses (simplex type 1, 2, and 3).

Side Effects

Garlic can cause nausea, stomach burn, and bad breath.

2) Oregano Oil

Oregano oil has been used for centuries as a food additive. It is known for its antimicrobial, antifungal, and antioxidant properties.

Mechanism of Action - The antibiotic and antifungal activity of oregano comes from two compounds, carvacrol and thymol. Thymol and carvacrol damage the cell exterior (membrane) of bacteria, killing the cell.

Antibacterial Activity - Oregano is effective against bacteria that cause food poisoning, urinary tract infections, diarrhoea, pneumonia, staph infections, and more. Thymol and carvacrol blocked the growth of cavity-causing bacteria (Streptococcus mutans), protecting rats against gum disease.

Mexican oregano oil together with thyme and mustard oils were effective against three different strains of bacteria (Listeria monocytogenes, Staphylococcus aureus, and Salmonella enteritis). Oregano oil together with clove and cinnamon oil inhibits the growth of the Acinetobacter baumannii, Acinetobacter baumannii RCH, Klebsiella pneumoniae, Escherichia coli, and Pseudomonas aeruginosa.

Antifungal Activity - Thymol and carvacrol were effective and stopping the growth of three different infection-causing fungi (yeast, Aspergillus, and dermatophyte).

Antiviral Activity - Carvacrol and thymol have antiviral activity against:

Herpes virus (simplex type 1), Human respiratory syncytial virus, Human rotavirus, Mouse norovirus.

Side Effects

Although rare, oregano oil can cause allergic reactions, especially in people with allergies to other members of the Lamiaceae family, like thyme.

3) Echinacea

Echinacea has been used as an herbal drug since the 18th century. Echinacea extracts are known for their antibacterial and immunoprotective properties.

Mechanism of Action - While the exact components of echinacea differ based on the species, the major ones are carbohydrates, caffeic acid, and proteins (glycoproteins). These are the active components that may have the antibacterial, antifungal, and antiviral properties.

Echinacea reduces symptoms of bacterial infections by blocking the release of inflammatory markers like cytokines. The mechanism for the antibacterial activity has not been clearly elucidated yet.

Antibacterial Activity - Echinacea is effective for reducing the growth of multiple bacterial strains such as Streptococcus pyogenes, Haemophilus influenzae, Legionella pneumophila, Clostridium difficile, and Propionibacterium acnes.

Antifungal Activity - Echinacea stops the growth of multiple strains of fungi and protected mice cells from lethal infections (Candida albicans and Listeria monocytogenes). It is also effective against Saccharomyces cerevisiae.

Antiviral Activity - Echinacea has antiviral activity against these viruses: Rhinovirus, Herpes viruses (simplex type 1 and 2), Influenza A and B, Respiratory syncytial virus.

Side Effects

Side effects from echinacea consumption are rare and include rash and mild stomach problems such as nausea and stomach aches.

4) Manuka Honey

Manuka honey is produced by bees that feed on the flowers of the manuka tree (Leptospermum scoparium). It is distinguished as the most medicinal honey.

Mechanism of Action - The main active antibiotic component of manuka honey is a compound called methylglyoxal. Another component of honey, propolis, has flavonoids (such as galangin and pinocembrin), phenolic acids, and esters that may contribute to boosting the immune system.

Manuka honey is also rich in glucose oxidase, an enzyme that converts glucose to hydrogen peroxide, which has antibacterial properties. Another compound, gluconolactone, reduces the pH of honey and has natural antibacterial properties. The inability of water to move through honey makes it difficult for bacteria to survive in it.

Antibacterial Activity - Manuka honey is a wide spectrum antibacterial and can kill the following bacteria: Escherichia coli, Staphylococcus aureus, several Enterococcus species, Pseudomonas aeruginosa, Streptococcus pyogenes, Proteus mirabilis, Salmonella typhimurium, and many more.

Topical application of manuka honey on a leg ulcer infected with antibiotic-resistant Staphylococcus aureus promoted effective wound healing in a patient on immunosuppressant drugs (case study).

Weekly honey consumption was associated with a decreased risk of Helicobacter pylori infection in 150 patients with digestion problems.

Antiviral Activity - Manuka honey inhibited the growth of the varicella-zoster virus (the cause of chickenpox and shingles) in human skin cells. It also inhibited influenza A virus growth in dog kidney cells.

Side Effects

Manuka honey taken for 4 weeks in 20 healthy adults caused no side effects. Although no allergic reactions were observed, caution is advised in individuals allergic to bees.

5) Red Pepper

Multiple variations of the red pepper (Capsicum annuum), such as the cayenne pepper, chilli peppers, and jalapeño peppers, have antibacterial properties.

Mechanism of Action - Capsaicin, the main active compound in peppers, which gives peppers their spicy taste, prevents bacterial infections by reducing stomach pH. Additionally, caffeic acid, quercetin, and kaempferol stiffen the outer layer (membrane) of bacterial cells, killing them.

A compound (CAY-1) in cayenne peppers kills fungi by disrupting the outer layer of the cells (increased cell membrane permeability).

Antibacterial Activity - Capsaicin restricted the production of α-toxins from Staphylococcus aureus and prevented pneumonia in mice.

Capsaicin blocked production of bacterial (Vibrio cholerae) toxins and prevented cell invasion by the bacteria (Streptococcus pyogenes and Staphylococcus aureus).

Antifungal Activity - CAY-1 is effective against several species like Candida albicans, Aspergillus, Microsporum and more. Some of these fungi cause skin diseases such as athlete’s foot and ringworm.

Side Effects

Capsaicin in moderate amounts is considered safe but may cause stomach irritation.

Drug Interactions

The use of capsaicin may increase the risk of developing a cough in patients using drugs for high blood pressure (ACE inhibitors).

6) Tea Tree Oil

Tea tree oil is extracted from the tea tree plant (Melaleuca alternifolia) and is a wide spectrum antibiotic used on the skin. It is the active ingredient in many formulations used to treat skin infections.

Mechanism of Action - Several compounds in tea tree oil, called monoterpenes (terpinen-4-ol, Linalool, alpha-pinene, and alpha-terpineol) are responsible for the antimicrobial activity in tea tree essential oils.

Monoterpenes block energy production (cellular respiration) and disrupt the outer layer (membrane) of bacterial and fungal cells.

Antibacterial Activity - Tea tree oil is effective against bacteria causing skin infections, acne, pneumonia, food poisoning, and more. Some of the bacterial strains include Staphylococcus (aureus and epidermidis), Propionibacterium acnes, Pseudomonas aeruginosa, Staphylococcus, Salmonella, and Escherichia coli.

A cream and body wash containing tea tree oil (10% and 5% tea tree oil, respectively), used for 5 days, helped clear antibiotic-resistant Staphylococcus aureus skin infections (RCT with 236 hospitalized patients).

A 0.2% tea tree oil solution reduced Streptococcus mutans and other microorganisms in the saliva of 30 subjects (5-week RCT).14

Antifungal Activity - Tea tree oil is effective against the following fungi: Candida albicans, Aspergillus, Microsporum, Epidermophyton, and more. These fungi can cause skin diseases (such as athlete’s foot and ringworm) among other issues.

In a study of 117 patients, tea tree oil application twice a day for 6 months treated toenail infections (onychomycosis). It also helped cure athlete’s foot (tinea pedis) in a study with 137 patients when