Identification of Secondary Metabolites from Mexican Plants with Antifungal Activity against Pathogenic Candida Species

Abstract

In the last three decades, invasive fungal infections caused by Candida species have become an important public health problem, because they are associated with high rates of morbidity and mortality in immunocompromised and hospitalized patients. The diagnosis and treatment of candidiasis are difficult and usually inefficient. Accordingly, a diversity of available drugs, currently employed to attack candidiasis, frequently induce resistance in patients promoting toxicity due to long-term treatments. Therefore, development of accurate diagnoses and novel antifungals is of high priority to improve life’s quality and expectancy of individuals infected with this pathogen. Plants are invaluable sources of new biologically active compounds. Among the plants used in Mexico in traditional herbolary medicine which have empirically been demonstrated to have antifungal activity are Pedilanthus tithymaloides, Thymus vulgaris, and Ocimum basilicum. In the present study, we analyzed whether these plants contain metabolites with antifungal activity against five Candida species. The extracts from the different plant organs were obtained by macerating them in ethyl alcohol or hexane and filtering. The obtained extracts were preserved in amber flasks at 4°C until used. The minimum inhibitory concentrations (MICs) of the active compound were determined by a microdilution assay. In addition, the following secondary metabolites were identified: linalool (3,7-dimethylocta-1,6-dien-3-ol), eugenol (4-allyl-2-methoxyphenol), limonene (1-methyl-4-(1-methylethenyl)-cyclohexene), and borneol ([(2R)-1,7,7-trimethyl-2-bicyclo[2.2.1]heptanyl] formate). All these compounds were found in the three plants, traditionally used in everyday life, and proved to be effective against Candida species and therefore a viable alternative to conventional antifungals.

Silver nanoparticle biosynthesis utilizing Ocimum kilimandscharicum leaf extract and assessment of its antibacterial activity against certain chosen bacteria

“…MIC is the lowest concentration at which no colour change occurs [ 63 , 64 ], whereas MBC is the lowest concentration at which no growth is seen on a petri dish [ 65 ].…”

D-Limonene: Promising and Sustainable Natural Bioactive Compound

“…In several experiments, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that the overall shape, cytoplasmic homogeneity, and cell wall thickness of bacterial and fungal cells were significantly changed after D-limonene treatment. In addition, it includes increased cell membrane permeability, altered membrane potential, and decreased heat resistance; leakage of intracellular substances, such as proteins, lipids, and nucleic acids, was also observed and even cell lysis at high concentrations, which may be due to the lipophilic and hydrophobic properties of D-limonene that promote lipid solubilization in the plasma membrane [70,77,79,86,[110][111][112][113][114]. However, unlike bacteria, D-limonene affects ergosterol and β-1,3-glucan, which are unique to fungi.…”

“…was also observed and even cell lysis at high concentrations, which may be due to lipophilic and hydrophobic properties of D-limonene that promote lipid solubilization the plasma membrane [70,77,79,86,[110][111][112][113][114]. However, unlike bacteria, D-limonene affe ergosterol and β-1,3-glucan, which are unique to fungi.…”

“…According to transcriptomics studies, D-limonene at a MIC of 20 µL/mL interfered with the transcription of key enzyme genes of the glycolysis pathway, tricarboxylic acid cycle, and oxidative phosphorylation pathway in C. tropicalis [118] and, in another study, the ATP concentration of L. monocytogenes decreased significantly after exposure to D-limonene, the activity of the respiratory chain I-V complex decreased, and the protein units were downregulated, which indicated that D-limonene could inhibit the synthesis of the respiratory chain complex proteins in L. monocytogenes, interfering with its respiratory function and energy metabolism, which led to the death of the cells [79]. D-limonene can also interfere with the synthesis of cellular ATP by inhibiting the respiratory complex and the ATPase in C. albicans, thereby affecting the respiratory intensity and energy metabolism [114].…”

Silver nanoparticle biosynthesis utilizingOcimum kilimandscharicumleaf extract and assessment of its antibacterial activity against certain chosen bacteria

“…MIC is the lowest concentration at which no colour change occurs [61,62], whereas MBC is the lowest concentration at which no growth is seen on a petri dish [63]. Values are the mean ± SE.…”