Protein Determination and Soluble Amino Acids Prediction in Various Solvents Extracted Solutions of Indigenous Red Lentil and Moong Pulse through Direct UV- Visible Spectrophotometer Technique: A Comparative Study

Abstract

In this comparative study, direct protein determination have been done for indigenous Red lentil (Lens culinaris) and Moong pulse (Vigna radiata) (obtained from Muzaffarpur, Bihar) by UV-visible spectroscopy in three different solvents viz. double distilled water(ddH 2 O), ethyl alcohol (C 2 H 5 OH), and methyl alcohol (CH 3 OH). A few amino acids insolutions have also been predicted (not characterized) based on their peaks observed in UV-region by comparing them with the reported range of wavelengths. Protein concentrations in red lentils for ddH 2 O, C 2 H 5 OH, and CH 3 OH extracted solution were 7.480, 1.205, and 0.835mg/mL, respectively. While, in case of moong pulse, protein concentrations in ddH 2 O,C 2 H 5 OH, and CH 3 OHextractedparts were 6.415, 1.150, and 3.485 mg/mL, respectively. Inboth cases, ddH 2 O extracted part showed the highest concentration of proteins while red lentil showed higher concentration in C 2 H 5 OH followed by CH 3 OH and moong pulse showed higher concentration in CH 3 OH followed by C 2 H 5 OH. During comparison with known wavelength ranges for amino acids peaks, red lentil in ddH 2 O showed peaks for cysteine, phenylalanine, tryptophan, and tyrosine; in C 2 H 5 OH peaks were only for cysteine and traces of phenylalanine; while in CH 3 OH, peaks were for cysteine, phenylalanine, tryptophan, and tyrosine. Whereas, moong pulse in ddH 2 O showed peaks for cysteine, phenylalanine, tryptophan, and tyrosine; in C 2 H 5 OH and CH 3 OH peaks were observed only for cysteine and phenylalanine. This method concludes that local pulses are rich in protein and amino acids and aqueous solutions showed highest protein concentration in each case. This direct method of protein quantitation is effective in the determination of protein at wavelength 280 nm as well as prediction of a few amino acids based on their specific peaks in UV-region. The main purpose of this work was to perform a comparative analysis of the protein concentrations in three different solvent-extracted solutions of two indigenous pulses by the direct UV-Visible spectroscopic technique without using any chemical. It is well known that pulses are rich in 3 protein but in best of authors knowledge there is no report on this type of work for these local pulses using this direct and fast quantitation method. As alcohols are not the very suitable solvents for the protein extraction, however, this study was performed using methanol and ethanol along with ddH 2 O in order to assess the experimental results in these two alcohols also and compare them to each other.