Time-kill kinetics and antibacterial activity of root extract of Adenodolichos paniculatus (Hua) Hutch & Dalz (Fabaceae)

Medicinal plants have been used in treatment of illness from time immemorial. Adenodolichos paniculatus is a medicinal plant used for traditional remedy of sore throat infections. This study therefore, evaluated the antibacterial activities of the root extracts and time-kill kinetics of the most potent extract. Five extracts, obtained by maceration using n-hexane, chloroform, ethyl acetate, methanol and water sequentially were evaluated for antibacterial activities and time-kill kinetics against Streptococcus pyogenes, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli. Chloroform root extract at 100 mg/ml was active against Streptococcus pyogenes, Staphylococcus aureus and Pseudomonas aeruginosa with zones of inhibition 25.00, 21.00 and 14.75 mm respectively but not against Escherichia coli. Minimum inhibitory concentrations were 1.56, 6.25 and 25.00 mg/ml respectively and the minimum bactericidal concentrations were 3.12, 12.50 and 50.00 mg/ml. Complete elimination of S. pyogenes, S. aureus and P. aeruginosa was achieved at concentrations 1.56 mg/ml, 6.25 mg/ml and 25.00 mg/ml within 300, 720 and 960 minutes exposure respectively and at concentrations 3.12 mg/ml, 25.00 mg/ml and 50.00 mg/ml within 180, 300 and 720 minutes exposure respectively. Chloroform root extract has the potential to be used as antibacterial agent and was better than the other solvent extract two-fold. Keywords: Adenodolichos paniculatus; Antibacterial activity; Time-kill kinetics; Percentage reduction, Log reduction