Bioactivity Guided Isolation, Characterization and Quantification of an Anxiolytic Constituent - Kaempferol, from Melilotus officinalis Aerial Parts

Abstract

Numerous plants used in traditional system of medicine exhibit pharmacological properties with great potential for therapeutic applications in the treatment of anxiety disorders. The aerial parts of Melilotus officinalis (Fabaceae) have been used traditionally for the treatment of convulsions, insomnia and as a nervine tonic. Despite a long tradition of its use in nervous system disorders, no systematic phytochemical and pharmacological work has been carried out on this potential plant. The aim of the present study was to isolate the antianxiety constituent(s) from M. officinalis aerial parts following bioactivity guided fractionation approach. Ethanol extract was partitioned successively with ethyl acetate and butanol and all fractions were evaluated for antianxiety activity. The bioactive ethyl acetate fraction was further subjected to column chromatography to get seven fractions which were evaluated for antianxiety effect in elevated plus maze (EPM). The bioactive EAF₆ when subjected to column chromatography resulted in isolation of a flavonoid, which was characterized by standard spectral techniques and its anxiolytic activity was evaluated using EPM and mirror chamber model. TLC densitometric method was developed to quantify the isolated compound. The present study resulted in isolation of kaempferol, which exhibits potent anxiolytic activity at 2 mg/kg which was comparable to that of diazepam. The study validates the traditional use of the M. officinalis aerial parts as an anxiolytic. Kaempferol was found to be responsible for anxiolytic effect of M. officinalis aerial parts.

Key words:

• Melilotus officinalis
• Bioactivity directed fractionation
• antianxiety
• kaempferol
• TLC densitometry