effects of capsaicin after preincubation with piperine suggests that endogenous
CGRP might be depleted during preincubation with piperine. This is supported by
the immunohistochemical study, where a marked reduction of CGRP-I was found
after the incubation of the tissue with piperine. It has been demonstrated that CGRP
produces positive motropic responses and an increase in the formation of cyclic
AMP in the atria but not in ventricles of rats and also of guinea pigs. In the present
study, CGRP also did not show positive inotropic effects on the ventricular muscle.
However, these results are not in accordance with the demonstration that
CGRP-binding sites are present in both atrial and ventricular muscle membranes
(Sigrist et al. 1986). They showed that the number of receptors is highest in the
right atrium followed by the left atrium, and then the right and left ventricles. The
exact reasons for the difference in the effects of CGRP between the atria and
NH 2
H 2 N
O
OH
H 2 N
N H 2
O
NH 2
N
O
O
SCoA
O
O
O
O
SCoA
O
O
O
SCoA
O
OH
O
O
SCoA
O
O
O
N
O
Malonyl-CoA
NADPH
H 2 O
Piperonyl-CoA
Lysine
Cadaverine
5-Aminopentanal
LDC
CuAO
NH
Piperideine
Piperine
LDC: Lysine decarboxylase
CuAO: copper amine oxidase
NADPH: nicotinamide adenine
dinucleotide phosphate
CoA: coenzyme A
Fig. 22.1 Biosynthesis of piperine
22 Piperine: Sources, Properties, Applications …
761