Study of qualitative and quantitative content of amino acids in pumpkin seeds for further standardization of the herbal drug

Abstract Aim Literary sources on qualitative composition, quantitative content of biologically active substances, and standardization methods of pumpkin seeds have been studied. It has been established that, along with Δ7-sterols, whose action is associated with treatment of the prostate gland, pumpkin seeds contain amino acids, cucurbitin in particular, which are responsible for their antihelminthic effect. The aim is to study the qualitative and quantitative content of amino acids in domestic samples of pumpkin seeds in order to clarify the possibility of pumpkin seed standardization for this class of biologically active substances. Methods The investigation of the possibility of amino acids’ identification in the herbal drug by the thin-layer chromatography (TLC) method was carried out on silica gel 60 F254 plates, Merck and Silica gel 60, Merck, on aluminum and glass supports in a mixture of the following solvents: butanol–acetone–acetic acid–water (35:35:10:20). The conclusions have been made based on the presence of characteristic zones of amino acids in the chromatograms after the treatment with ninhydrin solution. Quantitative determination of amino acids in the herbal drug was carried out by absorption spectrometry using HP spectrophotometer HP-8453 UV-VIS, Hewlett Packard (USA). Results The chromatographic profile of the amino acid fraction of domestic samples of pumpkin seeds was studied using a TLC technique. In the chromatograms of test solutions from all samples, the zones were detected at the level of histidine, aspartic acid, glutamic acid, glycine, and leucine zones, as well as a zone with color (olive) that differs from the other zones of amino acids and which is possibly a zone of cucurbitin. On the basis of the results of qualitative research, the quantitative content of the sum of amino acids according to a UV method developed has been determined, which including purification from the fatty oil, further extraction with an aqueous alcohol solution, selection of aliquots for the reaction with ninhydrin solution, and subsequent determination of the absorbance of the test solution and the solution of glutamic acid at a wavelength of 400 nm. It has been established that the content of the sum of amino acids expressed as glutamic acid in domestic samples is about 2%. Conclusions The research of the possibility of pumpkin seed standardization by the content of amino acids was carried out. The chromatographic profile of the amino acid fraction of domestic samples of pumpkin seeds was studied using a TLC method developed. The quantitative content of the amino acids sum by the absorption spectrophotometry method was investigated. The techniques developed will be recommended for inclusion in the draft of national monograph “Pumpkin seeds.”