Essential Oils of Lamiaceae Family Plants as Antifungals

The incidence of fungal infections has been steadily increasing in recent years. Systemic mycoses are characterized by the highest mortality. At the same time, the frequency of infections caused by drug-resistant strains and new pathogens e.g., Candida auris increases. An alternative to medicines may be essential oils, which can have a broad antimicrobial spectrum. Rich in the essential oils are plants from the Lamiaceae family. In this review are presented antifungal activities of essential oils from 72 Lamiaceae plants. More than half of these have good activity (minimum inhibitory concentrations (MICs) < 1000 µg/mL) against fungi. The best activity (MICs < 100) have essential oils from some species of the genera Clinopodium, Lavandula, Mentha, Thymbra, and Thymus. In some cases were observed significant discrepancies between different studies. In the review are also shown the most important compounds of described essential oils. To the chemical components most commonly found as the main ingredients include β-caryophyllene (41 plants), linalool (27 plants), limonene (26), β-pinene (25), 1,8-cineole (22), carvacrol (21), α-pinene (21), p-cymene (20), γ-terpinene (20), and thymol (20).


Introduction
Fungal infections belong to the most often diseases of humans. It is estimated that about 1.7 billion people (25% of the population) have skin, nail, and hair fungal infections [1]. The development of most of these infections is affected by dermatophytes, namely Trichophyton spp., Microsporum spp., and Epidermophyton spp. [2]. Simultaneously, mucosal infections of the oral and genital tracts caused by Candida spp. are very common. About 0.13 billion of women suffer from vulvovaginal candidiasis. On the other hand, oral candidiases are common in babies and denture wearers. Fungi also cause life-threatening systemic infections, with mortality reaching >1.6 million, which is >3-fold more than malaria [3]. Among life-threatening fungal infections prevail cryptococcosis (Cryptococcus neoformans) with >1,000,000 cases and mortality rate 20-70%, candidiasis (Candida albicans) with >400,000 cases and mortality rate 46-75%, pneumocystosis (Pneumocystis jirovecii) with >400,000 cases and mortality rate 20-80%, and aspergillosis (Aspergillus fumigatus) with >200,000 cases and mortality rate 30-95% [1, 4,5]. In Table 1 are presented diseases caused by some of the most often fungal pathogens among people. Table 1. Fungal pathogens of humans and most often observed mycoses (based on [6,7] The big problem is growing drug-resistance amid fungi. Among Candida and Aspergillus species is observed resistance to azoles, e.g., to fluconazole, voriconazole, and posaconazole. Some Candida species, especially C. glabrata and C. parapsilosis, can be echinocandin-and multidrug-resistant [8,9]. Acquired resistance to echinocandins has also been reported for yeasts C. albicans, C. tropicalis, C. krusei, C. kefyr, C. lusitaniae, and C. dubliniensis [10]. More than 3% of Aspergillus fumigatus isolates are resistant to one or more azoles [11]. Polyene resistance mainly concerns amphotericin B. Resistance to this drug is observed in Fusarium spp., Trichosporon spp., Aspergillus spp., and Sporothrix schenckii [12,13]. Resistance to amphotericin B has also been reported for C. albicans, C. glabrata, and C. tropicalis [14][15][16]. Cultures of some Candida species and Cryptococcus neoformans are presented in Figure 1. The big problem is growing drug-resistance amid fungi. Among Candida and Aspergillus species is observed resistance to azoles, e.g., to fluconazole, voriconazole, and posaconazole. Some Candida species, especially C. glabrata and C. parapsilosis, can be echinocandin-and multidrug-resistant [8,9]. Acquired resistance to echinocandins has also been reported for yeasts C. albicans, C. tropicalis, C. krusei, C. kefyr, C. lusitaniae, and C. dubliniensis [10]. More than 3% of Aspergillus fumigatus isolates are resistant to one or more azoles [11]. Polyene resistance mainly concerns amphotericin B. Resistance to this drug is observed in Fusarium spp., Trichosporon spp., Aspergillus spp., and Sporothrix schenckii [12,13]. Resistance to amphotericin B has also been reported for C. albicans, C. glabrata, and C. tropicalis [14][15][16]. Cultures of some Candida species and Cryptococcus neoformans are presented in Figure 1. The new epidemiological problem is C. auris, a multidrug-resistant organism first described in Japan in 2009 [17]. Recently, C. auris has been reported from 36 countries from six continents [18]. About 30% of isolates demonstrate reduced susceptibility to amphotericin B, and 5% can be resistant to the echinocandins [19,20]. The estimated mortality from C. auris fungemia range from 28% to 60% [21].

Candida albicans C. krusei
Fundamental issues are also the costs of treatment and hospitalization of patients with invasive fungal diseases. According to Drgona et al., all costs range from around €26,000 up to over €80,000 per patient [5]. Therefore, all time, new treatments for fungal infections are being sought. One option may be to apply natural products having antifungal activity. Among these, significant importances have essential oils, which can have a broad antimicrobial spectrum. Rich in the essential oils are among other plants from the Lamiaceae family.
In this review are presented antifungal activities of essential oils from seventy-two (72) plants of the Lamiaceae family. Moreover, are shown the most important compounds of these essential oils. For objective comparison of results, in this paper were included only antifungal studies specifying the minimum inhibitory concentrations (MICs) for essential oils. The MIC (expressed in µg/mL) is the lowest concentration of an antimicrobial agent in which no growth of a microorganism is observed in an agar or broth dilution susceptibility test [22][23][24].

Components of Essential Oils of Lamiaceae Family
The family Lamiaceae or Labiatae contains many valuable medicinal plants. In the family are The new epidemiological problem is C. auris, a multidrug-resistant organism first described in Japan in 2009 [17]. Recently, C. auris has been reported from 36 countries from six continents [18]. About 30% of isolates demonstrate reduced susceptibility to amphotericin B, and 5% can be resistant to the echinocandins [19,20]. The estimated mortality from C. auris fungemia range from 28% to 60% [21].
Fundamental issues are also the costs of treatment and hospitalization of patients with invasive fungal diseases. According to Drgona et al., all costs range from around €26,000 up to over €80,000 per patient [5]. Therefore, all time, new treatments for fungal infections are being sought. One option may be to apply natural products having antifungal activity. Among these, significant importances have essential oils, which can have a broad antimicrobial spectrum. Rich in the essential oils are among other plants from the Lamiaceae family.
In this review are presented antifungal activities of essential oils from seventy-two (72) plants of the Lamiaceae family. Moreover, are shown the most important compounds of these essential oils. For objective comparison of results, in this paper were included only antifungal studies specifying the minimum inhibitory concentrations (MICs) for essential oils. The MIC (expressed in µg/mL) is the Biomolecules 2020, 10, 103 4 of 35 lowest concentration of an antimicrobial agent in which no growth of a microorganism is observed in an agar or broth dilution susceptibility test [22][23][24].
In Table 2 are presented the main chemical components of essential oils of selected Lamiaceae family plants. Plant names were unified according to The Plant List [32], however synonyms used in the literature were also left. Chemical component names were unified, according to PubChem [33].   Hymenocrater longiflorus Benth.

Essential Oil Main Chemical Components References
Marrubium vulgare L.

Essential Oil Main Chemical Components References
Moluccella spinosa L.

Essential Oil Main Chemical Components References
Zataria multiflora Boiss.

Antifungal Activity of Essential Oils of Lamiaceae Family
In Table 3 are shown the antifungal activities of selected Lamiaceae essential oils. More than half of the essential oils have good activity (<1000 µg/mL) against fungi. In some cases are observed significant discrepancies between different studies. An example could be the action of essential oils from Italian Calamintha nepeta against Candida albicans. In the work of Marongiu et al. [39], minimal inhibitory concentrations amounted to 1.25-2.5 µg/mL, while in Božović et al. [40] MICs were between 780 to 12,480 µg/mL. Differences may be related to the different biochemical composition of the examined essential oils. In results presented by Marongiu et al. [39] the main components of  Table 1.

Antifungal Activity of Essential Oils of Lamiaceae Family
In Table 3 are shown the antifungal activities of selected Lamiaceae essential oils. More than half of the essential oils have good activity (<1000 µg/mL) against fungi. In some cases are observed significant discrepancies between different studies. An example could be the action of essential oils from Italian Calamintha nepeta against Candida albicans. In the work of Marongiu et al. [39], minimal inhibitory concentrations amounted to 1.25-2.5 µg/mL, while in Božović et al. [40] MICs were between 780 to 12,480 µg/mL. Differences may be related to the different biochemical composition of the examined essential oils. In results presented by Marongiu et al. [39] the main components of essential oils were pulegone (39.9-64.4%), piperitenone oxide (2.5-19.1%) and piperitenone (6.4-7.7%), while in Božović et al. [40] three main substances were pulegone (37.7-84.7%), crysanthenone (1.3-33.9%) and menthone (0.5-35.4%). Some authors have described that the content of active substances varies depending on the season. In studies of Gonçalves et al. [60] in Mentha cervina during the flowering phase in August amount of isomenthone and pulegone in essential oil amounted 8.7% and 75.1% respectively. Simultaneously, in the vegetative phase in February, the content of both components changed significantly and amounted to 77.0% for isomenthone and 12.9% for pulegone. Similarly, Al-Maskri et al. [75] presented essential changes in some compounds of Ocimum basilicum essential oil between winter and summer. In the summer essential oil, there is significantly more of linalool, p-allylanisole and β-farnesene, and at the same time much less content of limonene and 1,8-cineole. In this work, a seasonal variation of chemical composition is directly related to other antifungal activities. It is particularly evident in action against Aspergillus niger, which was lower in the summer season. Zone of growth inhibition (ZOI) for winter essential oil was 21 mm and MIC > 50 µg/mL, while for summer essential oil-ZOI was 13 mm and MIC > 100 µg/mL [75]. Influence on the content of chemical substances in essential oils also has a method of obtaining them.Ćavar et al. [40] compared the composition of oils obtained from Calamintha glandulosa using three methods: Hydrodistillation (HD), steam distillation (SD) and aqueous reflux extraction (ARE). For example, the level of menthone was 3.3% in ARE, 4.7% in HD, and 8.3% in SD method, while for shisofuran was only 0.1% in HD and SD, and even 9.7% in ARE [40]. Additionally, many other factors can affect antimicrobial activity, such as amount and concentration of inoculum, type of culture medium, pH of the medium and incubation time. All these factors can affect the value of MIC [145]. Differences are visible in Table 2. Generally, it can be assumed that the best activity (MICs < 100) have essential oils from Clinopodium spp. The mode of action of essential oils is multidirectional. Essential oils lead to disruption of the cell wall and cell membrane through a permeabilization process. The lipophilic compounds of essential oils can pass through the cell wall and damage polysaccharides, fatty acids, and phospholipids, eventually making them permeable [146,147]. Change of the permeability for H + and K + cations affects cellular pH and damage of cellular organelles [148,149]. Additionally, essential oils inhibit the synthesis of fungal DNA, RNA, proteins, and polysaccharides [150]. Essential oils can also disintegrate mitochondrial membrane [151,152]. It has also been shown that essential oil from Thymus vulgaris inhibits the production of aflatoxins by Aspergillus flavus and leads to the reduction of ergosterol production [123].

Essential Oils of Lamiaceae Plants in Cosmetics and Medicines
Some essential oils of Lamiaceae family plants and/or their components are commonly used in cosmetics and less often in medicine. Essential oils from Thymus vulgaris, Origanum vulgare, Rosmarinus officinalis, Calamintha officinalis, Salvia officinalis, or Lavandula officinalis are in cosmetic formulations as natural preservatives [187]. Lavandula angustifolia oil is commonly used as a fragrance in cosmetics, soaps, perfumes and pharmaceutical products. It also acts as an anti-inflammatory, and is calming, headache relieving, is a sedative and is skin healing. Essential oils from Lavandula hybrida and L. angustifolia also have anti-louse activity. Compounds (essential oils and mainly menthol) extracted from Mentha piperita are commonly used as a fragrance in soaps, cosmetics and as well as in the kitchen as a spice and refreshing products. Moreover, they are often found in chewing gums, toothpastes, and mouthwashes. For medical use, it can be taken orally in gastrointestinal complications. Rosmarinus officinalis essential oil is often an ingredient as a fragrance in cosmetics, soaps, bath salts and oils, gels and ointments. It is widely used for hair care and hair-loss treatment because it promotes hair growth and helps against dandruff [188]. In medicine, essential oils from Lamiaceae family are used in aromatherapy (Salvia sclarea, Lavandula officinalis, Mentha piperita, Rosmarinus officinalis) [189], sinusitis (Lavandula officinalis, Thymus vulgaris) [190], and in upper respiratory tract for treatment of catarrh (Mentha piperita, Mentha arvensis, Thymus spp.) [191]. Both essential oils from Lamiaceae plants and mono-substances are used in toothpastes and mouthwashes. In many of these the following chemicals, like limonene, linalool, menthol, and thymol, are presented as flavorings and fragrances [192,193]. Additionally, in some toothpastes are essential oils, e.g., in "Parodontax ® " occurs Salvia officinalis oil, Mentha piperita oil, and Mentha arvensis oil; in "Lacalut Active Herbal" is Mentha arvensis oil, Thymus vulgaris oil, and Salvia officinalis oil, while in "Signal Family Herbal Fresh" are oils from Mentha piperita and Salvia officinalis [194]. Literature data confirm a strong antifungal effect against C. albicans and anti-inflammatory activity of "Parodontax" toothpaste [195,196]. Besides toothpastes, also some medicines used to rinse the oral cavity or throat contain a large number of essential oils. Mention may be made of "Salviasept" having in its composition the oils from Mentha × piperita, Thymus vulgaris, Thymus zygis, Origanum majorana, and Salvia officinalis or "Dentosept Complex" containing oils from Mentha piperita, Thymus vulgaris, Salvia sp., Lavandula sp., and Eucalyptus globulus. Among the antifungal medicines in "Acerin Talk" antifungal foot deodorant are present Lavandula sp. oil, menthol, linalool, limonene, and geraniol, while in "Podoflex Tincture" for nails mucosis occur among others oils from Salvia sclarea and Lavandula angustifolia and mono-substances current in Lamiaceae plants: geraniol, limonene, linalool, citral, and eugenol [194].

Conclusions
More than half of the essential oils from Lamiaceae family plants have good antifungal activity (MICs < 1000 µg/mL). The microbiological data indicate that they could be used alone or in combination with antifungal drugs in the treatment of fungal infections, especially of the skin and mucous membranes. Some essential oils and their components extracted from Lamiaceae plants are used in cosmetics and medicines. Essential oils may be of future relevance in the treatment of multi-drug resistant fungi.