Analysis of Lunasin in Commercial and Pilot Plant Produced Soybean Products and an Improved Method of Lunasin Purification

Abstract

Lunasin is a bioactive peptide present in soybean. It is important to quantify lunasin concentration in soy products to assess its potential impact as functional food. The objectives of this study were to analyze lunasin in commercial soymilk products and implement an efficient method to isolate and purify it from defatted soybean flour. Defatted soybean flour was suspended in water, and the extract was loaded in a pre-equilibrated diethylaminoethyl column and bound proteins eluted using a step gradient of salt. Most lunasin was eluted from the column at 0.2 to 0.4M NaCl as quantified by immunoassays and purified using ultracentrifugation and ultrafiltration techniques. Lunasin purity was ≥90% and a standard curve was used to quantify its concentration in soymilk products. Concentration of lunasin in soy products, including organic soymilk, soy protein shakes, and soy infant formulas, ranged from 1.78 to 9.26 mg lunasin/100 g product. The concentration per serving ranged from 1.59 ± 0.01 to 22.23 ± 0.74 mg lunasin with variability depending on brand and size per serving. Steam-ground-cooked soy had the highest concentration of lunasin (22.23 ± 0.74 mg/serving), similar to some commercial products. Ground-cooked soymilk contained roughly half the concentration of lunasin (14.39 ± 1.4 mg/serving). Soy infant formulas that used soy protein isolate revealed lower concentrations of lunasin (P < 0.05). It was concluded that all soymilk products analyzed contained lunasin, and a more efficient method to isolate lunasin with higher purity was developed.

“Potential Health Benefits of Lunasin: A Multifaceted Soy‐Derived Bioactive Peptide”

“…Lunasin concentration may vary according to product storage condition, method of preparation, environmental factors, and type of soy genotype used in manufacturing the product. Lunasin concentration in different soy preparations has been extensively detailed by Cavazos and others (). Recently, considerable amount of highly stable lunasin was reported in oats (Avena sativa L) (Nakurte and others ).…”

“…Lack of proper methods is a major hindrance to get lunasin in its concentrated or purified form (Seber and others ; Hernandez‐Ledesma and others ). Recently, Cavazos and others () have developed a method resulting in >90% purity of lunasin from defatted soy flour. However, Seber and others () developed an improved resulting >99% purity of lunasin from same source by the application of more advanced techniques, namely, anion‐exchange chromatography, ultrafiltration, and reversed‐phase chromatography.…”

Endocytic Mechanism of Internalization of Dietary Peptide Lunasin into Macrophages in Inflammatory Condition Associated with Cardiovascular Disease

“…Lunasin is a 43-amino acid peptide that was originally isolated from soybeans and contains a unique Arg-Gly-Asp (RGD) cell-adhesion motif that is responsible for its bioactive properties [3]. Lunasin has been demonstrated to be bioavailable in humans after the consumption of soy protein foods and biologically active in tissues from rats [4], [5].…”

1997-2012: Fifteen Years of Research on Peptide Lunasin

“…Presence of lunasin has been demonstrated in commercial and pilot plant produced soybean products, including soy milk, infant formula, high protein soy shake, tofu, bean curd, soybean cake, tempeh, and su-jae (Table 1) [22,23]. Results from these studies establish the influence on lunasin concentration in the food products of different parameters, such as the soy genotype, the environmental factors, the manufacturing process and the storage conditions.…”

“…To date, the reported methods to isolate and purify lunasin from soybean only allowed obtaining small quantities of this peptide at 80% purity [70]. However, recently, Cavazos and co-workers (2012) have developed an improved method to isolate and purify lunasin from defatted soy flour, resulting in at least 95% purity [23]. Simultaneously, a large-scale method to generate highly purified lunasin from defatted soy flour has been developed by Seber and co-workers (2012) [78].…”