Phytochemical Screening and Antifungal Potential of Rhynchoglossum obliquum Ethanolic Leaf Extract Against Candida albicans and Aspergillus niger

Abstract

This study generated baseline data on the phytochemical constituents and in vitro antifungal activity of Rhynchoglossum obliquum Blume, an understudied medicinal plant reported in local folk medicine. Leaves were air-dried and extracted with ethanol, yielding a crude extract equivalent to 16.2% of dried plant material. Qualitative phytochemical screening confirmed the presence of alkaloids, flavonoids, saponins, and tannins. The antifungal activity of the crude ethanolic leaf extract was evaluated against Candida albicans and Aspergillus niger using the agar well diffusion method and broth macrodilution assay for minimum inhibitory concentration (MIC) determination. Ketoconazole (20 mg/mL, 50 µL) and 5% dimethyl sulfoxide (DMSO) served as the positive and negative controls, respectively. The extract exhibited concentration-dependent antifungal activity, producing mean zones of inhibition of 14.3 ± 0.2 mm, 11.6 ± 0.6 mm, and 11.1 ± 0.8 mm against C. albicans and 22.2 ± 0.5 mm, 21.4 ± 0.3 mm, and 20.2 ± 0.2 mm against A. niger at extract concentrations of 200, 150, and 100 mg/mL, respectively. In broth macrodilution testing, all concentrations tested (12.5–200 mg/mL) produced at least 50% growth inhibition after background correction for extract pigmentation, with an MIC of ≤12.5 mg/mL for both test organisms. Since MIC determination for the crude extract was performed independently of the ketoconazole dilution series, direct comparisons of potency were not appropriate. These findings provide scientific evidence supporting the antifungal potential of R. obliquum leaf extract and establish baseline data for future studies involving bioassay-guided fractionation, compound isolation, toxicity evaluation, and mechanism-of-action studies.