Antibacterial and antibiofilm activities of extract and bioactive compounds from Bergenia ciliata (Haw.) Sternb. flowers against Streptococcus mutans through cell membrane damage

Bergenia ciliata (Haw.) Sternb. (Family Saxifragaceae) remains mentioned as Pashanbheda in Ayurveda and Zakhmehayat in Unani. In North Waziristan, Pakistan, indigenous communities use this plant in ethnodentistry to treat tooth decay and toothaches. However, scientific evidence on its mode of action is still lacking. To evaluate the effect of extracts and fractions of B. ciliata flower against oral bacteria and elucidate the possible antibacterial and antibiofilm mechanism. Prepared extract of B. ciliata flowers were checked for its antibacterial activity against oral (S. mutans, S. pyogenes, S. oralis) and opportunistic bacteria (Staphylococcus aureus, Citrobacter clonae and Achromobacter insolitus). Preparative TLC-bioautography and silica gel column chromatography was used to isolate bioactive compounds. HRESI-MS and NMR studies were employed for its structural elucidation. Antibacterial and antibiofilm activities of extracts and isolated compounds were studied against S. mutans. Scanning Electron Microscope studies indicated membrane damage. Reactive Oxygen Species (ROS) production, lipid peroxidation and cytoplasmic leakage were also assessed. The most active ethyl acetate extract (EA) showed potent inhibitory effect against S. mutans (0.390 μg/μl). TLC–bioautography indicated spots F1 & F2 to show inhibition zones. F1 was identified as kaempferol. This is the first report on flowers of B. ciliata against oral infection. The mode of action of F1 can be attributed to its ability to destroy the membrane integrity, reducing and disrupting biofilm. It also produced ROS within the bacterial cell, leading to lipid peroxidation and subsequently causing death of the bacteria. Kaempferol is the active compound in bioactive spot F1 which showed antibacterial and antibiofilm activity. The antibacterial activity can be linked with the membrane disrupting properties of kaempferol and producing ROS inside S. mutans. Thus, phytochemicals derived from B. ciliata can be used in the development of pharmaceutical dental products. [Display omitted]