The rising incidence of non-albicans Candida (NAC) species and their developing resistance to traditional antifungal medications make candidiasis a significant problem in clinical microbiology. Another factor that leads to persistence and treatment failure is biofilm development. The purpose of this study was to assess the antifungal, antibiofilm, and synergistic properties of an ethanolic extract of Curcuma longa (C. longa), which was dried and then reconstituted in distilled water, against clinical isolates of Candida, with chemical characterization confirmed by Fourier Transform Infrared (FT-IR) spectroscopy. Using the Vitek 2 technique, chromogenic agar, and the germ tube test (GTT), 40 Candida isolates were identified from a variety of clinical cases. Using the broth microdilution to detect Minimal Inhibitory Concentration (MIC) and disc diffusion techniques, antifungal susceptibility was assessed in compliance with CLSI (2022) recommendations. Combination disc testing was used to evaluate the synergy between C. longa extract and fluconazole or amphotericin B, and the crystal violet microtiter plate assay was used to examine the antibiofilm activity. The chemical composition of the extract was analyzed by FT-IR (Bruker TENSOR 37, Kalkar, Germany) in the 450–3500 cm⁻¹ range. Candida species that are non-albicans accounted for the majority (67.5%), with C. glabrata being the most common isolate (50%). The ethanolic extract of C. longa showed modest antifungal activity, with MIC values ranging from 6.4 to 815 µg/mL and mean inhibition zones of 12.33 ± 7.17 mm. The extract exhibited significant synergistic effects with fluconazole (p < 0.001) and amphotericin B (p = 0.05), resulting in enhanced inhibition zones when compared to the medicines alone. Significant antibiofilm properties were also shown by the extract, which, on average, prevented biofilm formation by 31.7%. FT-IR analysis revealed prominent absorption bands at 3424.55 cm−1 (O–H stretching, phenols), 1650.44 cm−1 (C = O stretching, amides), and 1161.08 cm−1 (C–O stretching, ethers), confirming the presence of bioactive functional groups such as polyphenols, curcuminoids, and terpenoids, which are associated with antifungal and antioxidant activity. Curcuma longa’s ethanolic extract, when reconstituted in distilled water, showed encouraging antifungal and antibiofilm properties and enhanced the effectiveness of common antifungal medications. These results point to C. longa extract as a viable natural adjuvant treatment option for treating Candida infections linked to biofilms and overcoming antifungal resistance. FT-IR characterization confirmed the presence of key functional groups related to curcumin derivatives, supporting its potential as a natural adjunctive therapeutic candidate for managing biofilm-associated Candida infections and combating antifungal resistance.

In vitro evaluation of Curcuma longa extract for antifungal, antibiofilm, and synergistic activity against Candida spp.

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2026年7月6日

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Hanaa F. Abdel-Aty,
Abdullah M. Abdo,
Reham M. Raafat Hamed

摘要

The rising incidence of non-albicans Candida (NAC) species and their developing resistance to traditional antifungal medications make candidiasis a significant problem in clinical microbiology. Another factor that leads to persistence and treatment failure is biofilm development. The purpose of this study was to assess the antifungal, antibiofilm, and synergistic properties of an ethanolic extract of Curcuma longa (C. longa), which was dried and then reconstituted in distilled water, against clinical isolates of Candida, with chemical characterization confirmed by Fourier Transform Infrared (FT-IR) spectroscopy. Using the Vitek 2 technique, chromogenic agar, and the germ tube test (GTT), 40 Candida isolates were identified from a variety of clinical cases. Using the broth microdilution to detect Minimal Inhibitory Concentration (MIC) and disc diffusion techniques, antifungal susceptibility was assessed in compliance with CLSI (2022) recommendations. Combination disc testing was used to evaluate the synergy between C. longa extract and fluconazole or amphotericin B, and the crystal violet microtiter plate assay was used to examine the antibiofilm activity. The chemical composition of the extract was analyzed by FT-IR (Bruker TENSOR 37, Kalkar, Germany) in the 450–3500 cm⁻¹ range. Candida species that are non-albicans accounted for the majority (67.5%), with C. glabrata being the most common isolate (50%). The ethanolic extract of C. longa showed modest antifungal activity, with MIC values ranging from 6.4 to 815 µg/mL and mean inhibition zones of 12.33 ± 7.17 mm. The extract exhibited significant synergistic effects with fluconazole (p < 0.001) and amphotericin B (p = 0.05), resulting in enhanced inhibition zones when compared to the medicines alone. Significant antibiofilm properties were also shown by the extract, which, on average, prevented biofilm formation by 31.7%. FT-IR analysis revealed prominent absorption bands at 3424.55 cm⁻¹ (O–H stretching, phenols), 1650.44 cm⁻¹ (C = O stretching, amides), and 1161.08 cm⁻¹ (C–O stretching, ethers), confirming the presence of bioactive functional groups such as polyphenols, curcuminoids, and terpenoids, which are associated with antifungal and antioxidant activity. Curcuma longa’s ethanolic extract, when reconstituted in distilled water, showed encouraging antifungal and antibiofilm properties and enhanced the effectiveness of common antifungal medications. These results point to C. longa extract as a viable natural adjuvant treatment option for treating Candida infections linked to biofilms and overcoming antifungal resistance. FT-IR characterization confirmed the presence of key functional groups related to curcumin derivatives, supporting its potential as a natural adjunctive therapeutic candidate for managing biofilm-associated Candida infections and combating antifungal resistance.