Whatman filter paper No. 1 discs of 6 mm diameter were
sterilized using hot air oven at 160 °C for 1 h. Then 20 µL of
the test extract containing 100 mg/mL was introduced on
the sterile paper discs, and the solvents were allowed to
evaporate on a stream of air. The solvents used for dissolving
the extracts served as negative controls, while reference
antibiotics gentamicin (GM 10C; 10 µg) and tetracycline (T
10C; 10 µg) were used as positive control for Gram-negative
bacteria and Gram-positive bacteria, respectively.