Abstract
BackgroundThe root major proteins of sweet potato trypsin inhibitors (SPTIs) or named sporamin, estimated for 60 to 80% water-soluble proteins, exhibited many biological activities. The human low-density lipoprotein (LDL) showed to form in vivo complex with endogenous oxidized alpha-1-antitrypsin. Little is known concerning the interactions between SPTIs and LDL in vitro.ResultsThe thiobarbituric-acid-reactive-substance (TBARS) assays were used to monitor 0.1 mM Cu2+-mediated low-density lipoprotein (LDL) oxidations during 24-h reactions with or without SPTIs additions. The protein stains in native PAGE gels were used to identify the bindings between native or reduced forms of SPTIs or soybean TIs and LDL, or oxidized LDL (oxLDL). It was found that the SPTIs additions showed to reduce LDL oxidations in the first 6-h and then gradually decreased the capacities of anti-LDL oxidations. The protein stains in native PAGE gels showed more intense LDL bands in the presence of SPTIs, and 0.5-h and 1-h reached the highest one. The SPTIs also bound to the oxLDL, and low pH condition (pH 2.0) might break the interactions revealed by HPLC. The LDL or oxLDL adsorbed onto self-prepared SPTIs-affinity column and some components were eluted by 0.2 M KCl (pH 2.0). The native or reduced SPTIs or soybean TIs showed different binding capacities toward LDL and oxLDL in vitro.ConclusionThe SPTIs might be useful in developing functional foods as antioxidant and nutrient supplements, and the physiological roles of SPTIs-LDL and SPTIs-oxLDL complex in vivo will investigate further using animal models.
Highlights
The root major proteins of sweet potato trypsin inhibitors (SPTIs) or named sporamin, estimated for 60 to 80% water-soluble proteins, exhibited many biological activities
Effects of Sweet potato trypsin inhibitors (SPTIs) on Cu2+‐mediated low-density lipoprotein (LDL) oxidation and SPTIs bound to oxidized LDL (oxLDL) Figure 1a showed results of the Cu2+-mediated LDL oxidations during 24-h without or with SPTIs additions
It was found that the LDL oxidation (TBARS formation) was growing rapidly, and 4-h reaction reached to the top and gradually decreased
Summary
The root major proteins of sweet potato trypsin inhibitors (SPTIs) or named sporamin, estimated for 60 to 80% water-soluble proteins, exhibited many biological activities. The protein stains in native PAGE gels were used to identify the bindings between native or reduced forms of SPTIs or soybean TIs and LDL, or oxidized LDL (oxLDL). The native or reduced SPTIs or soybean TIs showed different binding capacities toward LDL and oxLDL in vitro. Huang et al (2008) reported that BALB/c mice fed normal diet concurrent with SPTIs (100 mg/kg) by gavaging once every 2 days for 35 days They found that the SPTIs interventions showed significantly to increase plasma antioxidant activities by ABTS method and reduce hepatic malondialdehyde (MDA) and plasma triglyceride levels compared to the control (P < 0.05 or 0.01), no significant change of plasma low-density-lipoproteins (LDL)-cholesterol (C) level was reported. The BALB/c mice fed high-fat diet containing 0.5% or 5% SPP (W/W of high-fat diet) for 28 days significantly showed to reduce body weight, epididymal fats and mesenteric fats, plasma triglyceride, and LDL-C compared to those in the control fed high-fat diet only
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