Antioxidant and antimicrobial activity of selected medicinal plants against human oral pathogens

Abstract

Objective: The aim of the study was focused on determining the phytochemicals, antibacterial, antiadherence, antifungal and antioxidant activities of Glycyrrhiza glabra, Matricaria chamomilla and Eclipta alba and also their mechanism of action towards human oral pathogens. Methods: Qualitative analysis and quantitative estimation of phenols and flavonoids were performed in methanolic extracts. Antibacterial, anti adherence, antifungal assays were performed by plate assays. Antioxidant assays were done by ABTS and DPPH methods. SEM, TEM and flow cytometry analysis were executed to find out the mechanism of action of plant extract. Results: The total phenol contents were 0.85, 1.24, 0.64 GAE/g and the total flavonoid contents were 356, 231.34 and 88 µg QE/mg for G. glabra, M. chamomilla and E. alba respectively. Matricaria chamomilla possesses highest antioxidant activity (DPPH and ABTS assays) among the all extracts tested. E. alba showed a highest zone of inhibition against S. aureus (21.6 mm) whereas G. glabra and M. chamomilla revealed the better result of 21 mm and 19.8 mm respectively against S. mutans. Glycyrrhiza glabra showed antifungal activity against Candida parapsilosis whereas Pseudomonas aeruginosa, Candida krusei, Candida tropicalis and Candida albicans showed resistance towards all the extracts tested. The MIC, MBC and antiadherence tests were also performed. Sorbitol assay confirmed that G. glabra has no impact on the fungal cell wall. To confirm the mode of action SEM, TEM and flow cytometric analysis were performed which showed the cell elongation and damage in cytoplasmic membrane resulting in oozing of cellular constituents. Conclusion: This work concluded that all the plant extracts showed potent activities among the various tests. Oral care product can be developed if the active constituents responsible for the activities were analysed.