Browsing by Author "Wickramasinghe, S. S."

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Comparative analysis of anticandidal potential between Cinnamomum zeylanicum (Ceylon Cinnamon) leaf and bark extracts against clinically isolated Candida species
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Wanigasekara, D. N.; Wickramasinghe, S. S.; Wijayaratne, G. B.; Napagoda, M. T.
Antifungal resistance has emerged as a major concern, hindering the treatment of fungal infections and prompting the development of new therapeutic options. Plant extracts have received attention for their potential as novel antifungal agents due to their various chemical entities and traditional use in indigenous medicinal systems. Cinnamomum zeylanicum (Ceylon cinnamon) has demonstrated promising antibacterial effects due to its extensive phytochemical profile. This study focuses on the antifungal properties of C. zeylanicum leaf and bark extracts against various Candida species, comparing their Minimum Inhibitory Concentrations (MICs) and Minimum Fungicidal Concentrations (MFCs) to fluconazole, a conventional antifungal agent. Candida species tested included C. albicans, C. parapsilosis, C. krusei, C. glabrata, C. tropicalis, C. famata, C. rugosa, C. dubliniensis, C. utilis, and C. guilliermondii. The obtained MICs depict that C. zeylanicum leaf extract has significant antifungal activity against numerous Candida species, with MIC values ranging from 0.0016 to 0.0102 mg/mL. In contrast, the bark extract had slightly higher MICs for most species, ranging from 0.0040 mg/mL to 0.0256 mg/mL. Fluconazole exhibited MIC values ranging from 0.0016 mg/mL to 0.0102 mg/mL for most species but was ineffective against C. glabrata, which was resistant to fluconazole. Notably, C. zeylanicum leaf extract has very low MICs against C. glabrata and C. krusei, indicating potency comparable to fluconazole. Furthermore, the MFCs of C. zeylanicum extracts demonstrate anticandida activity. MFCs in the leaf extract range from 0.0016 mg/mL to 0.1600 mg/mL, but in the bark extract, they range from 0.0040 mg/mL to 0.1600 mg/mL. These findings support the leaf extract's capacity to successfully kill Candida, while the bark extract likewise exhibits fungicidal activity across all tested species. In conclusion, C. zeylanicum leaf extract exhibits remarkable antifungal efficacy against various Candida species, indicating its potential as a natural alternative or adjuvant to conventional antifungal medications. The found efficacy against fluconazole-resistant species such as C. glabrata and C. krusei emphasizes the necessity of further investigation into C. zeylanicum extracts for therapeutic uses. Future studies should focus on understanding the mechanisms of action and performing clinical trials to validate these findings in real-world healthcare settings.
Interactions between penicillin and aqueous extracts of Plectranthus amboinicus and Plectranthus zeylanicus against Staphylococcus aureus.
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Hafsa, M. F. F.; Darshana, D.; Wickramasinghe, S. S.; Tennakoon, S. H.; Napagoda, M. T.
Penicillin, the pioneering antibiotic, has declined in effectiveness against Staphylococcus aureus due to increasing resistance, highlighting the urgent need for alternative strategies. Combining penicillin with medicinal plant extracts, such as Plectranthus amboinicus (Kapparawalliya) and Plectranthus zeylanicus (Iriveriya), rich in antibacterial compounds, offers a promising approach to revitalising its therapeutic efficacy. This study aimed to evaluate the potential interactions between penicillin and the aqueous extracts from P. amboinicus (PA) and P. zeylanicus (PZ) against both Methicillin-sensitive S. aureus (MSSA) and Methicillin-resistant S. aureus (MRSA). Whole plants of PA and PZ were macerated in distilled water for 24 hours at room temperature to prepare aqueous extracts. In the preliminary screening, the antibacterial activity of the aqueous extracts (500 mg/mL), and penicillin (3 mg/mL) were evaluated individually using the well-diffusion method. Ciprofloxacin (2 mg/mL) and distilled water were used as positive and negative controls, respectively. Subsequently, the minimum inhibitory concentration (MIC) of penicillin against MSSA and MRSA was determined using the broth microdilution method, followed by subculturing to determine minimum bactericidal concentrations (MBC). Aqueous extracts of PA and PZ were combined with different penicillin concentrations (2×MIC, MIC, 1/2×MIC, 1/4×MIC). The antibacterial activity of these combinations against MSSA and MRSA was evaluated using the well-diffusion method (well-diameter = 6 mm), measuring the inhibition zone diameter (IZD). The IZD of MIC of penicillin was compared with the IZD of penicillinPA and penicillin-PZ combinations to determine the interactions. Results showed that the aqueous extracts of PA and PZ did not demonstrate inhibition zones against MSSA and MRSA. The MIC and MBC of penicillin against MSSA were determined as 0.052 µg/mL and 100 µg/mL, respectively. However, the MIC of penicillin against MRSA was indeterminable, with an MBC exceeding 100 µg/mL. Notably, most combinations of penicillin with PA and PZ exhibited significantly higher IZD compared to MIC of penicillin alone (no inhibition zones), against both MSSA and MRSA (p < 0.05). Among all the combinations, the highest IZD was observed with the MIC+PZ combination against both MSSA and MRSA (IZD = 12.78 mm and 11.89 mm respectively). Potentiation was observed for the penicillin-PA combination, at penicillin concentration corresponding to the MIC against MSSA and at MIC, 1/2×MIC, 1/4×MIC against MRSA. With PZ, potentiation against MSSA and MRSA occurred at a penicillin concentration equivalent to the MIC. Additionally, penicillin combined with PZ demonstrated significantly stronger potentiation (p < 0.05) compared to penicillin-PA combinations, at equal penicillin concentrations, against both strains. In conclusion, the aqueous extracts from PA and PZ potentiated the antibacterial effectiveness of penicillin against MSSA and MRSA. This underscores the promise of these combinations for potent antibacterial therapies, suggesting a potential avenue for repurposing and reintroducing penicillin in combination with plant extracts to address antibiotic resistance. Further research should focus on understanding the mechanisms that enhance the effectiveness of penicillin when combined with PA and PZ.