Evaluation of Antimicrobial Activities of Different Extracts from Phlomis tuberosa, Abutilon fruticosum, and Nepeta transcaucasica

The use of medicinal plants for the natural treatment of infections has received much attention. Pre¬viously, plants of Nepeta, Phlomis, and Abutilon genera showed remarkable antimicrobial activities. We aimed to evaluate the antimicrobial effects of three Iranian plants including Abutilon fruticosum Guill. & Perr., Nepeta transcaucasica Grossh., and Phlomis tuberosa (L.) Moench. Aerial parts of the plants were extracted by the maceration method using petroleum ether, chloroform, ethyl acetate (EtAc), and methanol solvents. The antimicrobial activity of the extracts against seven Gram-positive strains and three Gram-neg-ative strains was studied via the disk diffusion method. Potent extracts were fractionated and diameters of the inhibition zone (DIZ) and Minimum Inhibitory Concentration (MIC) were determined. The chloroform extract of N. transcaucasica and EtAc extract of A. fruticosum were the most active extracts. Staphylococ¬cus aureus, was the most sensitive strain to N. transcaucasica (DIZ=17 mm, MIC=3.125 mg/ml), whereas S. epidermidis (DIZ=15 mm, MIC=1.56 mg/ml), and Bacillus subtilis (DIZ=13mm, MIC=0.39 mg/ml) were the most sensitive bacteria to A. fruticosum. Fractions of 40% and 60% EtAc/n-hexane of chloroform extract of N. transcaucasica and fractions of 40%-100% of EtAc extract of A. fruticusum revealed the potent activities. B. cereus was “very sensitive” to 60%-100% fractions of chloroform extract of N. trans¬caucasica (DIZ=16–19 mm, MIC=12.5 mg/ml). S. pneumoniae was “extremely” (DIZ=20 mm) sensitive to the 60% Ethyl acetate fraction of A. fruticosum and noticeably, their antimicrobial effects were greater than that of the standard antibiotic. The results support some of the traditional applications of the studied plants.