I am debating with pharmacology colleagues whether ampicillin and amoxicillin, which possess an NH2 group and, the latter, also an OH group more than penicillin G are more hydrophilic or more lipophilic than penicillin G. I always explain to students that aminopenicillins are more hydrophilic, and, therefore, pass more easily through Gram negative bacteria LPS, via the porins. My colleagues instead think that amoxicillin and ampicillin are more lipophilic and diffuse better through lipids of Gram negative lipid outer layer. Who is right?
Pubchem lists the logP of the compounds as follows:
penicillin G (benzylpenicillin): 1.8
amoxicillin: -2
ampicillin: -1.1
LogP is the octanol:water partition coefficient, a measure of hydrophobicity. The higher the number, the more hydrophobic the compound.
Amoxicillin and ampicillin, are more hydrophilic than benzylpenicillin.For more plz read at following link.
Regards
https://books.google.iq/books?id=NpN0CL7xYi4C&pg=PA82&lpg=PA82&dq=Ampicillin+and+amoxicillin+vs+benzylpenicillin,+which+is+more+hydrophilic?&source=bl&ots=L74QqZhZQh&sig=P3PYP5iA5TU1rBQFJEYOogjIr_o&hl=ar&sa=X&ved=0ahUKEwjdybH7uc7KAhVow3IKHdUPAw8Q6AEIOzAE#v=onepage&q=Ampicillin%20and%20amoxicillin%20vs%20benzylpenicillin%2C%20which%20is%20more%20hydrophilic%3F&f=false
You are right. Ampicillin and amoxicillin are more polar / hydrophilic than benzylpenicillin ( Pen G) because of the presence of a polar group (NH2) in the amide side chain and (OH) in amoxicillin at para position. It is therefore because of this hydrophilic property that makes them to have high affinity to the Gram negative cell wall. hence these two compounds are indicated for both Gram (+) and (-) infection while Pen G is useful only for Gram (+) infection.
I think to, that Ampicillin and amoxicillin is more hydrophilic, than benzylpenicillin ?
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