Title: Sedative–hypnotic and anxiolytic effects and the mechanism of action of aqueous extracts of peanut stems and leaves in mice

Abstract

INTRODUCTION

Peanut stems and leaves (PSL) have traditionally been used as both a special food and a herbal medicine in Asia. The sedative–hypnotic and anxiolytic effects of PSL have been recorded in classical traditional Chinese literature, and more recently by many other researchers. In a previous study, four sleep‐related ingredients (linalool, 5‐hydroxy‐4′,7‐dimethoxyflavanone, 2′‐O‐methylisoliquiritigenin and ferulic acid), among which 5‐hydroxy‐4′,7‐dimethoxyflavanone and 2′‐O‐methylisoliquiritigenin were newly found in Arachis species, were screened by ultrahigh‐performance liquid chromatography coupled with quadrupole time‐of‐flight mass spectrometry (UHPLC/QTOF‐MS). In the current study, quantitative examination of the above four ingredients was conducted. Serious fundamental functional studies were done in mice, including locomotor activity, direct sleep tests, pentobarbital‐induced sleeping time tests, subthreshold dose of pentobarbital tests and barbital sodium sleep incubation period tests, to determine the material base for the sedative–hypnotic and anxiolytic effects of aqueous extracts of PSL. Furthermore, neurotransmitter levels in three brain regions (cerebrum, cerebellum and brain stem) were determined using UHPLC coupled with triple‐quadrupole mass spectrometry (UHPLC/QQQ‐MS) in order to elucidate the exact mechanism of action.

RESULTS

Aqueous extract of PSL at a dose of 500 mg kg⁻¹ (based on previous experience), along with different concentrations of the above four functional ingredients (189.86 µg kg⁻¹ linalool, 114.75 mg kg⁻¹ 5‐hydroxy‐4′,7‐dimethoxyflavanone, 32.4mg kg−1 2′‐O‐methylisoliquiritigenin and 44.44 mg kg⁻¹ ferulic acid), had a sedative−hypnotic effect by affecting neurotransmitter levels in mice.

CONCLUSION

The data demonstrate that these four ingredients are the key functional factors for the sedative–hypnotic and anxiolytic effects of PSL aqueous extracts and that these effects occur via changes in neurotransmitter levels and pathways.