Invasive fungal infections are quite prevalent during the last decade or so. In particular, Candida albicans which is a common human fungal pathogen, causes cutaneous , mucosal, and systemic candidiasis. Candida infects in immunocompromised conditions or to the patients undergoing long-term treatment with antifungal drugs. Infection commonly occurs in different body parts such as skin (Ringworm), onychomycosis (fungal infection of the toenails or fingernails), oral candidiasis (oropharyngeal candidiasis ) and vaginal infection (yeast infections) which occurs in almost 75% of adult women. The most common medicines/drugs use to treatment of fungal infections are Econazole, Fluconazole, Ketoconazole, , Alotrimazole, clotrimazole, which belongs to azole class of drugs. However, due to excessive use of these drugs, Candida spp have acquired resistance during the course of the treatment. The conventional treatment of fungal disease is limited and due to increasing the resistance of antifungal drugs has encouraged to find new options from natural sources particularly in aromatic plants and their essential oils, to exploit their antifungal properties.
Edible essential oils are extracted from the different types of medicinal and aromatic plants that are generally found in Himalaya area, temperate or warm countries. Essential oil is liquid phase, evaporative, transparent, colored, soluble in lipids and organic solvents (Benzene) that have a lower density than water. Many edible essential oils have proved scientifically anti-fungal properties which can help fight against the many common fungus species. A variety of chemical components occur in edible oils such as alcohol, phenol, hydrocarbon, sulphur which also contribute towards role as antifungal agent. Edible oil is important because of their antifungal, antibacterial, antiparasitic properties. The antifungal activity of essential oil is depending on the quantity of their chemical composition and single components. Edible essential oils have been used to prevent oral candidiasis, vaginal, and skin fungal infection etc. The essential oil and their components have different types of targets site. In general oil components act on the cell wall, cytoplasm, lipid binding and DNA binding site of the C. albicans. This article at a common platform summarizes the antifungal potential of some of the most common and prevalent edible oils.
Clove essential oil (Syzygium aromaticum)
Cloves essential oil has been used since ancient time. It is used as a medicine and ingredients in cooking. Generally clove plant are found in Sri Lanka, Indonesia, Brazil and India (Kerala and Tamilnadu). Clove essential oil is extracted from the flower bud part of the Syzygium aromaticum , which plays an important role for the treatment of fungal infection. Clove tree is commonly called as Laung in India. Clove oil contains diverse compounds namely Eugenol (80 to 88%), vanillin, caryophyllene, gallotannic acid, and oleanolic acid, which contains antifungal activities. Eugenol is the major chemical compound present around 82 to 88%. Eugenol inhibits the fungal growth by inhibition of ergosterol biosynthesis or germ tube formation (GFT), and it is also known to affect the mycelia growth. Clove oil is not only acts as an antifungal for treatment of oral candidacies and skin, but also helps improving the immune system. It is also used in many diseases such as tonsillitis, rheumatic problems, bronchitis, asthma, osteoporosis, breathing difficulty throat, toothache, gingivitis, and few other oral conditions.
Lemongrass essential oil (Cymbopogon citrates)
Lemograss oil is used in the form of cooking oil and treatment of many diseases since thousands of years all over the world. Lemon grass oils are extracted by steam distillation form the fresh leaves of the lemon grass and used in regular medicine as drugs for the treatment of different types of fungal diseases. It is also may prevent the growth of some fungal species. Lemongrass oil contains flavonoids, phenolic compounds and citral (65-85%) which is the major component of lemongrass oil. In addition to citral, the lemongrass oil also consists of small amount of geraniol which has proven antifungal potential. Similarly, Citral has antifungal properties that inhibit the growth of C. albicans. Lemongrass oil is used for the treatment of throat, urinary, Ring – worm and vaginal candidiasis.
Lavender essential oil (Lavandula angustifolia)
Lavender is a flowering plant and one of the most popular medicinal herbs since ancient times. Lavender oil is obtained from the flowers part of the Lavandula angustifolia plant. Lavender is well-known for its antifungal properties, and its main component are linalool (20 - 50%), linalyl acetate (30 – 60%) and Eucalyptol. The presence of linalool has effect on changing structure of lipid layer present in the cell wall of C. albicans. It is also inhibits the formation of C. albicans biofilms and reduce mature biofilms. The Biofilm plays an important role in the fungal infections as they exhibit enhanced resistance to antifungal drugs. Linalool shows the antifungal activity against C. albicans and it is also inhibits the germ tube formation (GTF). Lavender plant is the type of medicinal herb that is commonly used for the treatment of Athlete's foot (Athlete's foot, also known as Tinea pedis, a fungal infection that affects the foot); dermatophytes causing infection of the skin, hair and nail fungal infections.
Tea tree essential oil (Melaleuca alternifolia)
Tea tree essential oil (TTO) is obtained by steam distillation of the leaves of Melaleuca alternifoliate (Australian native plant). The main chemical components of tea tree oil are terpinen-4-ol, and γ-terpinene. Tea tree oil inhibits the germ tube formation (GTF), or mycelial changes in C. albicans. Tea tree oil thus inhibit properties that can be used to treat Candida infections, vaginal candidiasis. It has been also used to treat a mild form of Seborrhoeic dermatitis. Because of ability to kill the fungal species, it is used as antifungal edible oil. The in vivo studies have demonstrated that tea tree oil ointment has potential to treat cutaneous, vaginal, acne, and mucosal fungal infection. The amount of tea tree oil to be used in the treatment of fungal infections depends on the medical condition of patients. Tea tree oil may have beneficial effects against fluconazole-resistant oropharyngeal candidiasis as well.
Oregano oil (Origanum vulgare)
Oregano oil is dark yellow to pale brown oil which is obtained from the leaves/flowers part of the Origanum vulgare plant. Oregano oil and the oreganum vulgar plant have been used as a traditional medicine or food tasty agents. They contain antifungal properties and high content of phenolic derivatives such as carvacrol and thymol. It is also contains γ-terpinene, p-cymene. Oregano oil and carvacrol have antifungal properties that play an important role in inhibition of germination and mycelial growth of C. albicans in dose – dependent manner. For the existence of these microorganisms, the structure and function of the plasma membrane of the fungal cells is necessary. Carvacrol has been ability to bind to sterols in the C. albicans membrane. Alteration in the synthesis of plasma membrane results in damage and death of fungus. Oregano oil has been used as both an internal and external agent in treating fungal infections. Oregano oil is an important part of Ayurvedic application which has been traditionally used for treatment of many fungal infections like throat infections, skin, and nail fungal infections
Sesame oil (Sesamum indicum)
Sesame oil is naturally obtained from the Sesamum indicum plant. Sesame oil has antifungal properties as well as rich in vitamin E, vitamin B6, zinc, copper, flavonoid phenolic antioxidants. Sesame oil contains major chemical component sesamol, linoleic acid (41%), oleic acid (39%), palmitic acid (8%), stearic acid (5%). The presence of Linoleic acid (C18H32O2) and oleic acids in sesame oil shows antifungal activity against the human as well as the plant fungal pathogen. Candidiasis that develop in the mouth or throat is called "thrush" or orrophrenyl candidiasis; it is caused by due to the decreased of saliva secretion, or dry mouth. Linoleic acid is a polyunsaturated fatty acid, which shows the antifungal properties. The antifungal property of the linoleic acid is also attributed to inhibition in the mycileal growth of the C. albicans. Especially sesame oil has been used all over the Asian countries for cooking, including Japan, and its taste is well known to most Asians.
Thyme essential oil (Thymus vulgaris)
The thyme essential oil extracted from the Thymus vulgaris plant also possesses considerable antifungal activity. Thyme essential oil contains 20–54% thymol, a monoterpene phenolic compound. Studies reported that thymol has ability to inhibit the growth of C. albicans, biofilm formation and ergosterol biosynthesis and membrane integrity. Thymol also has ability to change the hyphal morphology which results in reduction of hyphal diameters and destruction of hyphal wall. Thymol is lipophilic in nature which makes it capable of protruding inside the cell membrane of fungus.
Kalonji Oil (Nigella Sativa)
Kalonji is a traditional medicinal herb. It is found different parts of the world, but mostly in Iran. Kalonji oil is extracted from the seeds of Nigella sativa medicinal herb. The Nigella sativa seed contain, proteins, carbohydrates, alkaloids, oils and essential oil. The major chemical components found in Kalonji oil are, thymoquinone, p-cymene (C10H14) etc. Kalonji oil has been strong antifungal activities, which is using for treating the various types of fungal disease.
Coconut oil (Origanum vulgare)
Coconut oil is used in the Ayurvedic treatment of fungal infections since thousands of year. Coconut oil is derived from coconut fruit. Coconut oil is rich in three different types of fatty acid like capric acid, caprylic acid and lauric acid. Caprylic acid is known as their antifungal properties and play an important role in treatment of fungal infections. Capric acid and lauric acid both are combined together to create powerful antifungal combination. This powerful antifungal combination kills Candida by interfering with the walls of their cells. As a fully natural antifungal, coconut oil is safe low risk and effective way to prevent Candida overgrowth.
The utility of natural plant-based oils in antifungal therapeutics is evident from wide ranges of studies. Research on essential edible oils has the potential to identify new bioactive compounds and formulate new functional products for the treatment of fungal infections.