Carnosol inhibits the growth and biofilm of Candida albicans

Antifungal bioactivity of Sarcococca hookeriana var. digyna Franch. against fluconazole-resistant Candida albicans in vitro and in vivo

ETHNOPHARMACOLOGICAL RELEVANCE

Sarcococca hookeriana var. digyna Franch. has been widely utilized in folk medicine by the Miao people in the southwestern region of China for treating skin sores which may be associated with microbial infection.

AIM OF THE STUDY

To investigate the antifungal bioactivity of S. hookeriana var. digyna against fluconazole-resistant Candida albicans in vitro and in vivo, as well as its underlying mechanism and the key bioactive component.

MATERIALS AND METHODS

The antifungal bioactivity of 80% ethanol extract of S. hookeriana var. digyna (SHE80) was investigated in vitro using the broth microdilution method, time-growth curve, and time-kill assay. Its key functional component and antifungal mechanism were explored with combined approaches including UPLC-Q-TOF-MS, network pharmacology and metabolomics. The antifungal pathway was further supported via microscopic observation of fungal cell morphology and examination of its effects on fungal biofilm and cell membranes using fluorescent staining reagents. In vivo assessment of antifungal bioactivity was conducted using a mouse model infected with C. albicans on the skin.

RESULTS

S. hookeriana var. digyna suppressed fluconazole-resistant C. albicans efficiently (MIC = 16 μg/mL, MFC = 64 μg/mL). It removed fungal biofilm, increased cell membrane permeability, induced protein leakage, reduced membrane fluidity, disrupted mitochondrial membrane potential, induced the release of reactive oxygen species, promoted cell apoptosis, and inhibited the transformation of fungi from the yeast state to the hyphal state significantly. In terms of mechanism, it affected sphingolipid metabolism and signaling pathway. Moreover, the predicted bioactive component, sarcovagine D, was supported by antifungal bioactivity evaluation in vitro (MIC = 4 μg/mL, MFC = 16 μg/mL). Furthermore, S. hookeriana var. digyna promoted wound healing, reduced the number of colony-forming units, and reduced inflammation effectively in vivo.

CONCLUSIONS

The traditional use of S. hookeriana var. digyna for fungal skin infections was supported by antifungal bioactivity investigated in vitro and in vivo. Its mechanism and bioactive component were predicted and confirmed by experiments, which also provided a new antifungal agent for future research.

Fangchinoline inhibits growth and biofilm of Candida albicans by inducing ROS overproduction

Infections caused by Candida species, especially Candida albicans, threaten the public health and create economic burden. Shortage of antifungals and emergence of drug resistance call for new antifungal therapies while natural products were attractive sources for developing new drugs. In our study, fangchinoline, a bis-benzylisoquinoline alkaloid from Chinese herb Stephania tetrandra S. Moore, exerted antifungal effects on planktonic growth of several Candida species including C. albicans, with MIC no more than 50 μg/mL. In addition, results from microscopic, MTT and XTT reduction assays showed that fangchinoline had inhibitory activities against the multiple virulence factors of C. albicans, such as adhesion, hyphal growth and biofilm formation. Furthermore, this compound could also suppress the metabolic activity of preformed C. albicans biofilms. PI staining, followed by confocal laser scanning microscope (CLSM) analysis showed that fangchinoline can elevate permeability of cell membrane. DCFH-DA staining suggested its anti-Candida mechanism also involved overproduction of intracellular ROS, which was further confirmed by N-acetyl-cysteine rescue tests. Moreover, fangchinoline showed synergy with three antifungal drugs (amphotericin B, fluconazole and caspofungin), further indicating its potential use in treating C. albicans infections. Therefore, these results indicated that fangchinoline could be a potential candidate for developing anti-Candida therapies.

Biochanin A Inhibits the Growth and Biofilm of Candida Species

The aim of this study was to investigate the antifungal activity of biochanin A (BCA) against planktonic growth and biofilms of six Candida species, including C. albicans, C. parapsilosis, C. glabrata, C. tropicalis, C. auris, and C. krusei. We applied various assays that determined (a) the antimicrobial effect on growth of Candida species, (b) the effect on formation of hyphae and biofilm, (c) the effect on the expression of genes related to hyphal growth and biofilm formation, (d) the influence on cell wall structure, and (e) the effect on cell membrane integrity and permeability. Moreover, disk diffusion tests were used to investigate the effect of a combination of BCA with fluconazole to assess their possible synergistic effect on drug-resistant C. albicans, C. glabrata, and C. auris. Our results showed that the BCA MIC50 values against Candida species ranged between 125 µg/mL and 500 µg/mL, and the MIC90 values were in a concentration range from 250 µg/mL to 1000 µg/mL. The treatment with BCA inhibited adhesion of cells, cell surface hydrophobicity (CSH), and biofilm formation and reduced hyphal growth in all the analyzed Candida species. Real-time qRT-PCR revealed that BCA down-regulated the expression of biofilm-specific genes in C. albicans. Furthermore, physical destruction of C. albicans cell membranes and cell walls as a result of the treatment with BCA was observed. The combination of BCA and fluconazole did not exert synergistic effects against fluconazole-resistant Candida.

Polyphyllin I, a strong antifungal compound against Candida albicans

This study was performed to explore the antifungal and antibiofilm effects of polyphyllin I (PPI) on Candida albicans. Microdilution assay was performed to determine the minimal inhibitory concentrations (MIC) of PPI against Candida species. Adhesion assay, hyphal growth assay, biofilm formation, and development were used to test the impacts of PPI on C. albicans virulence factors. Propidium iodide staining was performed to test whether the permeability of cell membrane was influenced by PPI. PPI showed significant antifungal activities against several Candida species, with MIC below or equal to 6.25 μM. PPI also inhibited the adhesion to polystyrene surfaces, hyphal growth, and biofilm formation. PPI significantly increased the permeability of C. albicans cell membrane. In sum, PPI can suppress the planktonic growth and biofilm of C. albicans and its mechanism involves the increased permeability of cell membrane.

Dehydrocostus lactone inhibits Candida albicans growth and biofilm formation

Candida albicans infections are threatening public health but there are only several antifungal drugs available. This study was to assess the effects of dehydrocostus lactone (DL) on the Candida albicans growth and biofilms Microdilution assays revealed that DL inhibits a panel of standard Candida species, including C. albicans, as well as 9 C. albicans clinical isolates. The morphological transition of C. albicans in RPMI-1640 medium and the adhesion to polystyrene surfaces can also be decreased by DL treatment, as evidenced by microscopic, metabolic activity and colony forming unit (CFU) counting assays. The XTT assay and microscopy inspection demonstrated that DL can inhibit the biofilms of C. albicans. Confocal microscopy following propidium iodide (PI) staining and DCFH-DA staining after DL treatment revealed that DL can increase the membrane permeability and intracellular reactive oxygen species (ROS) production. N-acetyl-cysteine could mitigate the inhibitory effects of DL on growth, morphological transition and biofilm formation, further confirming that ROS production induced by DL contributes to its antifungal and antibiofilm effects. This study showed that DL demonstrated antifungal and antibiofilm activity against C. albicans. The antifungal mechanisms may involve membrane damage and ROS overproduction. This study shows the potential of DL to fight Candida infections.

In vitro evaluation of the composition and acaricidal efficacy of Urtica fissa leaf ethyl acetate extract against Sarcoptes scabiei mites

In veterinary medicine, natural products provide an alternative to chemical agents for mite management. In the present study, the acaricidal efficacy of Urtica fissa leaf ethyl acetate extract against Sarcoptes scabiei mites was examined. The chemical composition of the extract was determined using liquid chromatography-mass spectrometry (LC-MS) analysis. The ethyl acetate extract was found to be extremely toxic to mites at a concentration of 100 mg/ml (m/v), killing all S. scabiei within two hours. The median lethal time (LT50) values for ethyl acetate extract concentrations of 25, 50, and 100 mg/ml against S. scabiei were 1.706, 1.204, and 0.750 h, respectively. The median lethal dosage (LC50) for S. scabiei was 19.14 mg/ml at two hours. The chemical composition of the ethyl acetate extract was evaluated using LC-MS, showing that the major components were schaftoside (8.259%), carnosol (6.736%), prostaglandin A2 (5.94%), 13(S)-HpOTrE (4.624%), nandrolone (4.264%), 1H-indole-3-carboxaldehyde (4.138%), 9-oxoODE (3.206%), and stearidonic acid (2.891%). In conclusion, these findings indicate that Urtica fissa contains promising new acaricidal compounds capable of successfully controlling animal mites.

Natural Compounds: A Hopeful Promise as an Antibiofilm Agent Against Candida Species

The biofilm communities of Candida are resistant to various antifungal treatments. The ability of Candida to form biofilms on abiotic and biotic surfaces is considered one of the most important virulence factors of these fungi. Extracellular DNA and exopolysaccharides can lower the antifungal penetration to the deeper layers of the biofilms, which is a serious concern supported by the emergence of azole-resistant isolates and Candida strains with decreased antifungal susceptibility. Since the biofilms’ resistance to common antifungal drugs has become more widespread in recent years, more investigations should be performed to develop novel, inexpensive, non-toxic, and effective treatment approaches for controlling biofilm-associated infections. Scientists have used various natural compounds for inhibiting and degrading Candida biofilms. Curcumin, cinnamaldehyde, eugenol, carvacrol, thymol, terpinen-4-ol, linalool, geraniol, cineole, saponin, camphor, borneol, camphene, carnosol, citronellol, coumarin, epigallocatechin gallate, eucalyptol, limonene, menthol, piperine, saponin, α-terpineol, β–pinene, and citral are the major natural compounds that have been used widely for the inhibition and destruction of Candida biofilms. These compounds suppress not only fungal adhesion and biofilm formation but also destroy mature biofilm communities of Candida. Additionally, these natural compounds interact with various cellular processes of Candida, such as ABC-transported mediated drug transport, cell cycle progression, mitochondrial activity, and ergosterol, chitin, and glucan biosynthesis. The use of various drug delivery platforms can enhance the antibiofilm efficacy of natural compounds. Therefore, these drug delivery platforms should be considered as potential candidates for coating catheters and other medical material surfaces. A future goal will be to develop natural compounds as antibiofilm agents that can be used to treat infections by multi-drug-resistant Candida biofilms. Since exact interactions of natural compounds and biofilm structures have not been elucidated, further in vitro toxicology and animal experiments are required. In this article, we have discussed various aspects of natural compound usage for inhibition and destruction of Candida biofilms, along with the methods and procedures that have been used for improving the efficacy of these compounds.