Anti-candidal activity of three medicinal plants with special reference to anti-virulent and anti-biofilm properties of pongamia pinnata
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Date
2014
Authors
Kanatiwela, H. M. D. K.
Journal Title
Journal ISSN
Volume Title
Publisher
University of Peradeniya
Abstract
Candida spp. is a commensal fungus found in human oral, gastrointestinal, vaginal and cutaneous surfaces. Immunocompromised individuals are pron e to this organi sm resulting in superficial and systemic infections. The infective ability of Candida is triggered by virulent features such as germ tube production, cell surface hydrophobicity (CS H), extracellular enzyme production etc. Tre ating candidal infectio ns have become a challenge due to the emergence of resistance to currently available antifungal drug s. Co lonization of this opportunistic pathogen, by the production of biofilms furt her incre ases resistance thereby resulting in a therapeutic dilemma. In overcoming this situation, plants have been recognized as important reservoirs of natural prod ucts , which can be utilized as antifungal agents. In this study, solvent extracts of different plant parts of selec ted three medicinal plants (viz. bark , roots and leaves of Pongamia pinnata, tlower bud s of Syzygium aromaticum and fruits of Piper nigrum) were screened for their anti-candidal activity.
Flower bud s of S. aromaticum showed the best anti -candidal acti vity and its minimum inhibitory concentrations (MIC) ranged from 0.4 to 1.6 mg/ml. Root s of P. pinnata showed positi ve activity while neither bark nor leaf sho wed positive acti vity. MICs of the root extracts ranged from 1.6 to 12.8 mg/ml. Fruits ofP . nigrum did not show inhibitory potential against any of the candidal isolates.
Detailed studies on anti -virulent properties ofP. pinnata were carried out when the organism was in contact with the extract and when the organism was pre-exposed to the extract. Long term pre-exposure (18 h) of the isolates to the concentrations less than MIC values result ed in a significant reduction in the germ tube formation and elongation (P<0.05). The isolates which were in contact with the extract achie ved a significant reduction (P<0 .05) in germ tube production and elongation when the y were provided with extracts with concentrati ons higher than MICs. It was revealed that reduced hyphal formation as well as hyphal elongation cou ld be achie ved by either long-term pre-exposure of the C. albicans isolates to the sub-inhibitory concentrations or in the presence of the extract in concentrations higher than MIC for a time period as short as 2 h. However, the pre-exposure did not affect the CSH (P>0.05). C. guilliermondii and C. dubliniensis when in contact with the extract for a short time period (in sub -inhibitory concentrations; 1.5 h), a drastic reduction of CSH was observed (P<0.05). Abo ve results impl y that the presence of the extract was required to achie ve a reduced CSH of Candida spp . as the pre-exposure did not affect the hydrophobic property of candidal isolates. Howe ver , the extracellular phospholipase production of the organism was not affected by both the presence and pre -exposure of Candida sp. to the extract.
Root extracts of P. pinnata were further tested for anti-biofilm property. The adhesion of two candidal isolates, which is the very first step of biofilm production, was significantly reduced by sub-inhibitory concentrations of the extract. However, results indicated a considerable increase in the level of biofilms when already initiated biofilms and matured biofilms were treated with even very high concentrations of the extract.
These findings suggest the possibility of using S. aromaticum and P. pinnata in medicated products to treat candidal infections. This is the first repo rt on the anti-candidal activity and anti-virulent potential of root extract of P. pinnata. How ever, the variability shown by the effects of P. pinnata on different growth phases and features of Candida spp. highlights the need of further investigations to explore possible applications of the extract in the pharmaceutical field.
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Keywords
Candida spp , Candida , Medicinal plants , Anti-candidal activity , Pongamia pinnata