Explore the potential of rice peptides in health promotion, showcasing their antioxidant capacity, ACE inhibition, and benefits in antihypertensive drug development.

Key words: rice peptide, ACE inhibitory activity, antihypertensive effect, Caco-2 cell

Introduction

The assessment of biomolecular mass has seen significant advancements with the use of Gel Permeation Chromatography (GPC/SEC), Multi-Angle Laser Light Scattering (MALLS), and Differential Refraction Detector (RI) technologies. These methods are among the most advanced and reliable for determining the molecular weight of biomolecules directly, without the need for column calibration or reference standards. This research focuses on the detailed analysis of rice peptides, examining their absolute molecular mass, amino acid composition, and their potential in vitro activities, such as antioxidant capacity and ACE inhibition.

Materials and Methods

Materials and Reagents

Rice from Hubei Fuwa Group, enzymes including alkaline protease and trypsin from Novo Nordisk, and other chemicals for analysis like Trolox, AAPH, DPPH, and ACE were sourced from Sigma, USA. Chromatographically pure acetonitrile was obtained from the China National Pharmaceutical Group Corporation, with all other reagents being of analytical grade.

Major Instruments

Instruments used include a high-performance liquid chromatograph, a visible spectrophotometer, a pH meter, a freeze dryer, a fluorescence plate reader, a centrifuge, a pure water system, a UV detector, and a conductivity meter.

Experimental Methods

The preparation of rice peptides involved two main methods: alkaline extraction of rice protein followed by enzymatic hydrolysis to produce rice peptides. The absolute molecular mass of the rice peptides was measured using SEC-MALLS-RI technology. The amino acid composition was determined by post-column derivation high-performance liquid chromatography, and the peptide content was quantified using the biuret method. The antioxidant capacity was evaluated using the DPPH radical scavenging method and the ORAC assay. ACE inhibition activity was assessed using high-performance liquid chromatography.

Results and Discussion

Determination of Absolute Molecular Mass

The analysis showed that rice peptides primarily ranged in molecular mass from 549 to 1158, with the highest proportion of peptides falling between 549 to 723. This is consistent with the molecular mass range of known ACE inhibitory and antioxidant peptides.

Amino Acid Composition

Rice peptides were found to have a high proportion of essential amino acids (about 35.61%) and hydrophobic amino acids (45.200%). The composition was particularly rich in glutamic acid, leucine, aspartic acid, tyrosine, phenylalanine, serine, proline, and alanine, suggesting a potentially strong ACE inhibitory and antioxidant activity.

Peptide Content

The peptide content in the rice peptides was determined to be 83.84 ± 1.44%, indicating a high purity of peptides suitable for further biochemical analyses.

Antioxidant Capacity

The rice peptides showed significant antioxidant capacity, with the DPPH radical scavenging IC50 value at 1.170mg/mL and the ORAC value at 1568.006 µmol Trolox/g. These results indicate that rice peptides possess considerable antioxidant activity.

ACE Inhibition Activity

The rice peptides demonstrated potent ACE inhibitory activity, with an IC50 value of 0.057mg/mL. This strong activity suggests that rice peptides could be beneficial in managing high blood pressure.

Conclusion

This study detailed the characterization of rice peptides, showing a significant potential in antioxidant activity and ACE inhibition. The absolute molecular mass, amino acid composition, and in vitro activities of rice peptides offer promising insights for the development of natural antioxidants, health foods, and antihypertensive drugs. The findings underscore the importance of rice peptides as valuable bioactive compounds for health promotion and disease prevention.

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The original research is done by WANG Shen,GONG Zhiyong(School of Food Science And Engineering, Wuhan Polytechnic University, Wuhan,430023, China) The ariticle ID is: doi: CNKI:CDMD:2.1015.537891