Densitometric analysis of kawain in kava-kava root extracts

A thin layer chromatographic-densitometric method for the identification and determination of kawain in a mixture of kavalactones obtained from a methanol extract of kava-kava roots (Piper methysticum) was developed. The main compounds present in the extract were separated with good results using silica gel F 254 coated TLC plates as the stationary phase and hexane-dioxane-butyl acetate-ammonia 25% (7:2:3:0.5 v/v/v/v) as the mobile phase. The qualitative identification and quantitative measurement of kawain were obtained by UV measurements at lambda=250 nm. The described method demonstrates very high sensitivity with the limit of detection established at 20 ng. 99.38% of the kawain was recovered and the concentration range showed a linearity from 0.0005% to 0.004%. Under these conditions, the percent of kawain in the presence of other kavalactones in the prepared extracts (I-VII), was determined. Similar results were obtained for all extracts, with the kawain content ranging from 1.01% to 1.16%.