evaluation of drying process on the composition of black pepper ethanolic extract by high performance liquid chromatography with diode array detector

background black pepper (piper nigrum) is one of the well-known spices extensively used worldwide especially in india, and southeast asia. the presence of alkaloids in the pepper, namely, piperine and its three stereoisomers, isopiperine, chavicine and isochavicine are well noticed. objectives the current study evaluated the effect of lyophilization and oven drying on the stability and decomposition of constituents of black pepper ethanolic extract. materials and methods in the current study ethanolic extract of black pepper obtained by maceration method was dried using two methods. the effect of freeze and oven drying on the chemical composition of the extract especially piperine and its three isomers were evaluated by hplc analysis of the ethanolic extract before and after drying processes using diode array detector. the uv vis spectra of the peaks at piperine retention time before and after each drying methods indicated maximum absorbance at 341.2 nm corresponding to standard piperine. results the results indicated a decrease in intensity of the chromatogram peaks at approximately all retention times after freeze drying, indicating a few percent loss of piperine and its isomers upon lyophilization. two impurity peaks were completely removed from the extract. conclusions in oven dried samples two of the piperine stereoisomers were completely removed from the extract and the intensity of piperine peak was increased.