Passionflower activities vary by extraction method.
Passiflora incarnata (passionflower) is indigenous to America but is utilised worldwide making an appearance in the pharmacopeias of Switzerland, Germany, France, Great Britain, India, the USA and a number of other countries. Its primary uses are in the treatment of anxiety, insomnia and epilepsy. To this date there has been a paucity of research clarifying the active constituents, although they are believed (on current evidence) to be the flavonoid components. Clinical trials have shown anxiolytic and sedative effects.
In preparation for a clinical trial in epilepsy sufferers, researchers in the United States conducted this research into the potential mechanisms of passionflower extracts and the impact of differing extraction methods on biological effects and extract components.
An initial whole plant extract was prepared by steeping the herb in 45% alcohol then freeze drying it to a powder containing 27.78 g fresh herb per 1 g of powder. When applied to a hippocampal slice preparation (mouse), this evoked a direct dose dependant increase in GABAA currents. However a later amino acid reduced extract had no effects, leading researchers to suggest that it was the [GABA.sub.A] in passionflower itself that induces changes in GABAergic transmission.
Following this experiment five further extracts were prepared from the same original source material. These were as follows:
1. Fresh herb steeped for 14 days in a 65:35 OH:[H.sub.2]O mix at 25[degrees]C.
2. Fresh herb extracted in water at 100oC for 75 minutes then 4[degrees]C for 21 hours.
3. Dried herb steeped for 14 days in a 65:35 OH:[H.sub.2]O mix at 4[degrees]C.
4. Dried herb extracted for 65 minutes in a 65:35 OH:[H.sub.2]O mix at 100oC then 19 hours in the same mix at 4[degrees]C.
5. Dried herb extracted for 60 minutes in water at 100[degrees]C then 20 hours in the same mix at 4[degrees]C.
These were then tested in animal models of epilepsy, anxiety and sensorimotor function. Extracts 2 and 3 reduced the frequency and severity of seizures. Surprisingly all extracts increased measure of anxiety compared with control mice. Those which were the most anxiogenic were extracts 3 and 5. There was no effect on sensorimotor function displayed by any of the herbal preparations. It is suggested that differences between botanical species tested, geographical source of plants, extraction methods, dose, method and duration of administration, vehicle used, test animal species and strain, baseline anxiety levels and potential effects of the extracts on activity levels might all contribute to the divergence between these findings and those of other studies demonstrating the anxiolytic effects of passionflower. They also suggest that perhaps certain flavonoid constituents show different dose/response profiles with increased anxiogenic effects at higher doses.
Researchers examined the differing constituents present in these five extracts but found no correlation between total flavonoid or GABA content and displayed activities. Unfortunately this study fails to shed definitive light on the true active ingredients of Passiflora incarnata, but suggests that further investigation (especially into potential synergism and biochemical activities) may be warranted.
Tessa Finney-Brown MNHAA
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|Title Annotation:||Reviews of articles on medicinal herbs|
|Publication:||Australian Journal of Medical Herbalism|
|Date:||Dec 22, 2010|
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