Effects of St. John's wort extract and single constituents on stress-induced hyperthermia in mice.
Level 5 - mechanism / opinion, no new human data
Animal experiment assessing stress-induced hyperthermia in mice
PubMed 17051457 · doi:10.1055/s-2006-951710
What was done
Male BL6/C57J mice were subjected to open-field (OF) exposure for 10 minutes as an acute stressor to induce stress-induced hyperthermia (SIH), calculated as the difference between basal and post-stress body temperature (DeltaT). The authors evaluated the effects of oral St. John's wort (SJW) extract (125–1000 mg/kg), positive control anxiolytics (diazepam 5 mg/kg, buspirone 10 mg/kg), antidepressants (imipramine, fluoxetine), and isolated SJW constituents: hypericin (0.1 mg/kg), hyperforin (1–10 mg/kg), flavonoids (hyperoside, isoquercitrin, quercitrin at 0.6 mg/kg; rutin at 1 mg/kg; miquelianin at 1.2 mg/kg), and the biflavonoid amentoflavone (0.1 mg/kg).
What was found
Open-field stress increased body temperature by DeltaT = 1.8 +/- 0.13 degrees C (p < 0.05). Diazepam and buspirone significantly reduced DeltaT, whereas imipramine and fluoxetine had no effect. SJW extract significantly reduced DeltaT at 250 and 500 mg/kg, with no effect at 125, 750, or 1000 mg/kg (a U-shaped dose-response). Hypericin (0.1 mg/kg) significantly reduced DeltaT (p < 0.05), while hyperforin had no effect. Flavonoids partially blocked hyperthermia, with miquelianin being the most potent. Amentoflavone (0.1 mg/kg) also decreased SIH. Exact numerical values for individual drug groups were not reported in the abstract.
Why it matters
The findings demonstrate that specific constituents of St. John's wort—notably hypericin, miquelianin, and amentoflavone—exert anxiolytic-like effects on autonomic stress responses in rodents, distinct from conventional monoaminergic antidepressants.
Limits
This is an animal study in male mice; findings cannot be directly translated to human clinical efficacy or dosing. Sample sizes per experimental group and exact numerical data or error bounds for most single constituents were not provided in the abstract.
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