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NEUROENDOCRINOLOGY LETTERS
including Psychoneuroimmunology, Neuro
psychopharmacology,
Reproductive Medicine, Chronobiology
and Human Ethology
ISSN 0172–780X

NEL Vol.23 No.4, August 2002

ORIGINAL RESEARCH PAPER
Presence of isoquinoline alkaloids in molluscan ganglia

2002; 23:329334
pii: NEL230402A07
PMID: 12195236

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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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