Antimicrobial and anti-biofilm activities of Diospyros lycioides root, leaf and twig extracts against Staphylococcus aureus and Mycobacterium avium

Abstract

This study utilised the minimum inhibitory concentration (MIC) assay and the microtiter plate assay to investigate the antimicrobial and anti-biofilm activities of D. lycioides crude methanolic extracts against Staphylococcus aureus and Mycobacterium avium. Thin layer chromatography was used to qualitatively screen for the presence of phytochemical compounds in the plant methanol and aqueous extracts. Phytochemical analysis revealed the presence of all tested compounds in the methanol extracts, except for saponin. These included coumarin, triterpenoids, anthraquinone, tannins, alkaloids, steroids and flavonoids. On average steroids, tannins, triterpenoids and anthraquinones were the most abundant phytochemicals in both aqueous and methanol extracts, with the highest
amounts observed in the methanol extracts. The minimum inhibitory concentration against M. avium occurred at 75mg/ml, 37.5mg/ml and 18.75mg/ml for the root, leaf and twig methanol extracts, respectively while for S. aureus all methanol extracts showed an MIC of 75mg/ml. The highest biofilm inhibition against S. aureus was due to the methanol extracts of D. lycioides leaves (57.2%) and roots (58.1%). However, the twig methanol extracts (57.8%) inhibited M. avium biofilm formation the most as compared to the leaf (25.6%) and root (35.3%) extracts. The leaf extracts (40.4%) were moderately active in eradicating S. aureus biofilms, whereas for M. avium
the highest eradication activity was observed with the root extracts (35.6%).