It should work as expected. Try to run the following example.
import pandas as pd
import io
data = """value
"2015-09-25 00:46" 71.925000
"2015-09-25 00:47" 71.625000
"2015-09-25 00:48" 71.333333
"2015-09-25 00:49" 64.571429
"2015-09-25 00:50" 72.285714"""
df = pd.read_table(io.StringIO(data), delim_whitespace=True)
# Converting the index as date
df.index = pd.to_datetime(df.index)
# Extracting hour & minute
df['A'] = df.index.hour
df['B'] = df.index.minute
df
# value A B
# 2015-09-25 00:46:00 71.925000 0 46
# 2015-09-25 00:47:00 71.625000 0 47
# 2015-09-25 00:48:00 71.333333 0 48
# 2015-09-25 00:49:00 64.571429 0 49
# 2015-09-25 00:50:00 72.285714 0 50