The quantitative EEG as a screening instrument to identify sedative effects of single doses of plant extracts in comparison with diazepam

Two multiple crossover studies, each involving 12 adult female subjects, were performed to screen for acute sedative effects of eight different plant extracts ( Valeriana off., Lavandula off., Passiflora incarnata, Kava-kava, Melissa off., Eschscholzia californica, Hypericum perforatum and Ginkgo biloba). Both studies were placebo-controlled, and a single dose of 10 mg diazepam was used as an active reference drug. All drugs were administered as a single dose. Prior to administration, as well as 2 h and 3 h after administration the EEG was recorded from two leads (F z-C z and O z-T 6) under vigilance-controlled and resting conditions, for five minutes each. The extend of tiredness was rated by the subjects on a visual analogue scale. The EEG was digitized and stored for later analysis of the absolute and relative power of seven factorially defined frequency bands. Under diazepam the power in the theta frequency band decreased while it increased in the beta band. In contrast, some plant extracts showed an increase of power in the theta frequency band, but no increase in the beta frequency range. Valerian extract, which was administered in both studies, displayed an increase of power in the delta and theta band and a decrease in the beta band. Self-rated tiredness increased under diazepam and under some of the plant extracts but not with placebo. The results show that sedating effects of plant extracts can be identified by quantitative EEG analysis and by self-assessment instruments.