Presence
of isoquinoline alkaloids in molluscan ganglia
Wei
Zhu 1, Yuliang Ma 2 & George B. Stefano
1
1.
Neuroscience Research Institute, State University of New York,
College at Old Westbury, Old Westbury, NY 11568, USA.
2. Skirball Institute of Biomolecular Medicine, New York University,
540 First Avenue, New York, NY 10016, USA.
Key
words:
morphine; invertebrate neural tissues; tetrahydropapaveroline;
reticuline; isoquinoline alkaloids; tetrahydroisoquinoline
alkaloids
Submitted:
July 25, 2002
Accepted: July 25, 2002
ABSTRACT
Tetrahydropapaveroline
and reticuline, isoquinoline alkaloids, were purified and
identified in the pedal ganglia of the marine mollusk Mytilus
edulis.
OBJECTIVES:
To determine the presence of tetrahydropapaveroline and reticuline,
isoquinoline alkaloids, in animal tissues previously shown
to express opiate receptors.
METHODS
AND RESULTS: This was achieved by high performance liquid
chromatography coupled with electrochemical detection and
finally identified by electro-spray ionization quadrupole
time of flight mass spectrometry (Q-TOF). The expression of
these two terahydroisoquinoline alkaloids in the animals neural
tissue is at the level of 2.5±0.64 ng/ganglion and
1.8±0.52 ng/ganglion, respectively.
CONCLUSION:
This finding suggests that morphine biosynthesis may occur
in Mytilus neural tissues, and that the biosynthesis pathway
may be similar to that reported in the poppy plant.
Introduction
Tetrahydroisoquinoline
alkaloids (TIQs) belong to a group of naturally occurring pharmacologically
active compounds. They are taken up, stored, and released from
nerve terminals, and interfere with normal catecholaminergic
transport and storage systems [1,2]. Among these TIQs, tetrahydropapaveroline
(THP) and reticuline are particularly interesting because of
their involvement in neural function and in morphine biosynthesis,
respectively. THP is an endogenous 1-benzyltetrahydroisoquinoline
previously found in both plant and animal tissues, including
human tissues [3,4]. It is synthesized by a non-enzymatic Pictet-Spengler
reaction of dopamine with 3,4-dihydroxyphenyl-acetaldehyde [5,6].
There is a large body of evidence that other opiate alkaloids,
such as morphine, thebaine, and codeine, exist in vertebrates
[7,8,9]. In invertebrates, specifically Mytilus edulis, the
presence of morphine, morphine 6 glucuronide, morphine 3 glucuronide
and codeine have been reported [10,11,12,13]. Taken together
these reports suggest that animals may have the ability to synthesize
opiate alkaloids.
At the present time, there is no documentation on the presence
of TIQs in invertebrates. Indeed, if morphine is made in these
tissues, its precursors should be identified. We now demonstrate
the presence of THP and reticuline in mollusk ganglionic tissue
by way of high pressure liquid chromatography (HPLC) coupled
to electrochemical detection and nano-flow electro-spray ionization,
double-quadrupole orthogonal-acceleration, and time of flight
mass spectrometry (Q-TOF MS) determination.
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