3. Results and discussion
The essential oil and different extracts of M. piperita were explored
for antioxidant activity by evaluating their antioxidant
capacity, DPPH free radical scavenging activity and reducing
power, and the results are given in Table 2. Chloroform extract
and peppermint oil showed almost equal antioxidant potency
(about 90%). Aqueous extract exhibited the least potency
among all. In DPPH free radical scavenging activity and
reducing power absorbance of both peppermint oil and chloroform
extract exhibited similar trends as observed in the case of
antioxidant capacity. Aqueous extract showed the least DPPH
scavenging activity (70.3 ± 6.1) and reducing power
(0.4 ± 0.3) akin to its antioxidant activity. The rest of the
leaves extracts showed the antioxidant capacity, DPPH scavenging
activity and reducing power in between those of chloroform
and aqueous extracts. The IC50 (lg/mL) of peppermint
oil by using DPPH scavenging method was found to be
15.2 ± 0.9 while for positive control BHT it was 6.1 ± 0.3.
The antibacterial activity of the M. piperita oil and different
extracts was assessed using the agar well diffusion method by
measuring the diameter of growth inhibition zones at different
concentrations. The results of antimicrobial activity of the peppermint
essential oil by the MHA well diffusion method are
presented in Figs. 1 and 2, Table 3. Both Gram +ve bacterial
species (S. aureus and S. pyogenes) tested were sensitive to peppermint
essential oil with the inhibition zone 17.2 and
13.1 mm, respectively. The inhibition zone for Gram –ve