دانلود رایگان مقاله تصفیه کاناوانین از سبزی نرم برگ ماشک

Abstract

Vicia disperma is an annual legume that accumulates high amounts of the non-protein amino acid canavanine in the seeds. The purification of this amino acid from the seeds of V. disperma has been investigated in order to assess the possibility of using this plant as a source of canavanine. Seeds had 3% (w/w) canavanine content, representing 84.3% (w/w) total free amino acids. Canavanine was extracted from seed flour extracts at pH 4 and purified by nanofiltration and ion-exchange chromatography, followed by either precipitation or crystallization, yielding canavanine 90% and 97% pure, respectively. This represents a simple and inexpensive procedure for production of canavanine, taking advantage of the high content of canavanine in V. disperma. This could have a very beneficial impact on the use of V. disperma and other Vicia rich in canavanine, some of which have good agronomic properties and were farmed in the past.

3. Results and discussion

3.1. Free amino acids and canavanine in V. disperma seeds Free amino acids were extracted from the seeds taken from nine populations of V. disperma using aqueous ethanol. Total free amino acids ranged from 2.55% to 3.55% (w/w), with an average content of 2.9970.31% (w/w). These values are much higher than those found in soy (0.42%), chickpea (0.45%), and lentil (0.67%), which were also analyzed as reference materials, and represent contents in total free amino acids that are ten times higher than the content in polyphenols as reported, 0.28% (w/w) (Pastor-Cavada et al., 2011a). Canavanine was the major free amino acid in V. disperma samples, ranging from 80.4% to 88.6%, and with an average content of 84.372.72% as referred to total free amino acids. Other free amino acids were present at much lower concentrations, including threonine, arginine, aspartic acid, asparagine, glutamic acid, and histidine, all of them at concentrations between 0.5% and 9% (w/w) in all populations (Table 1). Only traces of the remaining free amino acids were present. The predominance of a single free amino acid in V. disperma seeds, in this case canavanine, was less apparent in crop legumes. Thus, asparagine, arginine and threonine accounted for 24.8%, 52.2%, and 22.7% (w/w) total amino acids in soybean, chickpea, and lentil, respectively. The content in canavanine as referred to the whole seeds was between 2.2% and 3.0% (w/w) with an average content of 2.5470.25% (w/w) as referred to the flour, which is similar to the content in the most popular source of canavanine, the legume C. ensiformis (Rosenthal, 1977b) with 2.6% (w/w). The inter-population variability of the content in free amino acids and canavanine for the nine populations was low, suggesting that it is well fixed genetically and quite independent of environmental conditions.