In Vitro and In Vivo Anti- Candida spp. Activity of Plant-Derived Products

Abstract

Candidiasis therapy, especially for candidiasis caused by Candida non-albicans species, is limited by the relatively reduced number of antifungal drugs and the emergence of antifungal tolerance. This study evaluates the anticandidal activity of 41 plant-derived products against Candida species, in both planktonic and biofilm cells. This study also evaluates the toxicity and the therapeutic action of the most active compounds by using the Caenorhabditis elegans-Candida model. The planktonic cells were cultured with various concentrations of the tested agents. The Cupressus sempervirens, Citrus limon, and Litsea cubeba essential oils as well as gallic acid were the most active anticandidal compounds. Candida cell re-growth after treatment with these agents for 48 h demonstrated that the L. cubeba essential oil and gallic acid displayed fungistatic activity, whereas the C. limon and C. sempervirens essential oils exhibited fungicidal activity. The C. sempervirens essential oil was not toxic and increased the survival of C. elegans worms infected with C. glabrata or C. orthopsilosis. All the plant-derived products assayed at 250 µg/mL affected C. krusei biofilms. The tested plant-derived products proved to be potential therapeutic agents against Candida, especially Candida non-albicans species, and should be considered when developing new anticandidal agents.

Keywords: C. elegans; Candida; anticandidal agents; plant-derived products.

Figure 1

Kill assays for plant-derived products against Candida species. The concentrations 0.5 × MIC, 1 × MIC, and 2 × MIC correspond to: (A) Litsea cubeba × C. krusei: 31.25, 62.5, and 125 µg/mL; (B) Gallic acid × C.glabrata 31.25, 62.5, and 125 µg/mL; (C) Gallic acid × C. krusei: 62.5, 125, and 250 µg/mL; (D) Citrus limon × C. tropicalis: 125, 250, and 500 µg/mL; (E) Citrus limon × C. glabrata: 125, 250, and 500 µg/mL; (F) Cupressus sempervirens × C. orthopsilosis: 15.62, 31.25, and 62.5 µg/mL; (G) Cupressus sempervirens × C. glabrata: 15.62, 31.25, and 62.5 µg/mL. AMB: 4 µg/mL amphotericin B and Untreated: Candida species’ growth without plant-derived products. The results are expressed as the mean colony-forming units (CFU)/mL ± standard deviation from three independent experiments.

Figure 2

Survival curves of the responses to the tested compound concentrations from the Caenorhabditis elegans–Candida infected model. Nematode survival diminished at 0.5 × MIC, 1 × MIC, and 2 × MIC for all the compounds, except for the Cupressus sempervirens EO. (A)—C. elegans infected with C. glabrata and treated with C. sempervirens EO, (B)—C. elegans infected with C. glabrata and treated with C. limon EO, (C)—C. elegans infected with C. glabrata and treated with gallic acid, (D)—C. elegans infected with C. krusei and treated with L. cubeba EO, (E)—C. elegans infected with C. krusei and treated with gallic acid, (F)—C. elegans infected with C. tropicalis and treated with C. limon, (G)—C. elegans infected with C. orthopsilosis and treated with C. sempervirens. The untreated control group is represented by the green lines; the infected control, the fungicidal control drug (amphotericin B), and the different concentrations of the tested compounds are represented by symbols. The results were obtained from three independent experiments with at least three replicates.