Effects of traditionally used anxiolytic botanicals on enzymes of the γ-aminobutyric acid (GABA) systemThis article is one of a selection of papers published in this special issue (part 1 of 2) on the Safety and Efficacy of Natural Health Products

In Canada, the use of botanical natural health products (NHPs) for anxiety disorders is on the rise, and a critical evaluation of their safety and efficacy is required. The purpose of this study was to determine whether commercially available botanicals directly affect the primary brain enzymes resp...

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Bibliographic Details
Published in:Canadian journal of physiology and pharmacology 2007-09, Vol.85 (9), p.933-942
Main Authors: Awad, R, Levac, D, Cybulska, P, Merali, Z, Trudeau, V.L, Arnason, J.T
Format: Article
Language:English
Subjects:
acide γ-aminobutyrique
anxiety
botanicals
GABA transaminase
GABA-T
GAD
glutamate decarboxylase
glutamate décarboxylase
végétaux
γ-aminobutyric acid
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Summary:In Canada, the use of botanical natural health products (NHPs) for anxiety disorders is on the rise, and a critical evaluation of their safety and efficacy is required. The purpose of this study was to determine whether commercially available botanicals directly affect the primary brain enzymes responsible for γ-aminobutyric acid (GABA) metabolism. Anxiolytic plants may interact with either glutamic acid decarboxylase (GAD) or GABA transaminase (GABA-T) and ultimately influence brain GABA levels and neurotransmission. Two in vitro rat brain homogenate assays were developed to determine the inhibitory concentrations (IC 50 ) of aqueous and ethanolic plant extracts. Approximately 70% of all extracts that were tested showed little or no inhibitory effect (IC 50 values greater than 1 mg/mL) and are therefore unlikely to affect GABA metabolism as tested. The aqueous extract of Melissa officinalis (lemon balm) exhibited the greatest inhibition of GABA-T activity (IC 50 = 0.35 mg/mL). Extracts from Centella asiatica (gotu kola) and Valeriana officinalis (valerian) stimulated GAD activity by over 40% at a dose of 1 mg/mL. On the other hand, both Matricaria recutita (German chamomile) and Humulus lupulus (hops) showed significant inhibition of GAD activity (0.11-0.65 mg/mL). Several of these species may therefore warrant further pharmacological investigation. The relation between enzyme activity and possible in vivo mode of action is discussed.
ISSN:0008-4212
1205-7541
DOI:10.1139/Y07-083