Effects of Novel Extraction Strategies on the Recovery of Phenolic Compounds and Associated Antioxidant Properties from Buckwheat Hull (Fagopyrum esculentum)

Akanksha Joshi,Brijesh Kumar Tiwari,Shaba Noore,Bibha Kumari,Ming Zhao,Colm O’Donnell

doi:10.3390/pr10020365

Abstract

This study investigated the effects of novel extraction technologies, including ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), pulsed electric field (PEF), high-pressure processing (HPP), enzyme-assisted extraction (EAE), and conventional extraction, on the recovery of phenolic compounds and associated antioxidant properties from buckwheat hull (Fagopyrum esculentum). Initially, twenty-four extraction strategies were investigated. Based on the results of the total phenolic content and antioxidant properties (DPPH and FRAP), twelve strategies (i.e., US (n = 2), PEF (n = 1), MW (n = 4), HPP (n = 4), and a control method) were selected for phenolic profiling carried out using liquid chromatography-mass spectrometry (LC-MS). Forty-one phenolic compounds were identified in the extracts, and a scanning electron microscope (SEM) analysis was also carried out on the treated residues to analyze the surface damage post-treatments. The results showed that samples treated with US (16.14 ± 0.06), PEF (9.94 ± 0.02), MW (12.63 ± 0.13), and HPP (21.76 ± 0.78) contained the highest total phenolic content (mg GAE/100 mg of DW). In the case of the antioxidant activities, the highest DPPH activities were obtained using HPP, MAE, and UAE, while no clear pattern was recorded in the case of FRAP activities. The highest DPPH and FRAP activities observed were 80.91 ± 0.22% and 23.98 ± 0.2 mg Trolox equivalents/100 mg, respectively. Additionally, the LC-MS results identified eleven different groups of phenolic compounds in buckwheat hull extracts, including anthocyanin, flavanol, flavanones, flavones, flavonol, phenolic acids, isoflavones, lignans, and quinones.

Highlights

In the case of enzyme-assisted extraction (EAE), three types of enzymes namely cellulase, β-glucosidase, and viscozyme were employed and the maximum amount of extraction yield (8.10 ± 1.27 g/100 g) was recorded for the samples treated with cellulase
The effects of novel extraction strategies on the antioxidant properties of extracts obtained from buckwheat hull were examined, and the results indicated a large increase in the levels of both DPPH and Ferric Reducing Antioxidant Power (FRAP) compared to those from the control samples (Table 1)
This study suggests that the extraction level of antioxidants from buckwheat hull can be significantly improved by using novel extraction strategies

Summary

Introduction

China with a nutritional content higher than that of wheat or rice grain [1]. It belongs to the Polygonaceae family, and the two most cultivated species are Fagopyrum esculentum and Fagopyrum tataricum. A significant amount of hull is generated as a byproduct of buckwheat processing [3] These hulls are rich in proteins (5.13–5.68%), fats (0.50–0.81%), minerals (1.88–2.06%), starch (0.15–2.26%), and carbohydrates (91.72–92.19%) [4]. Buckwheat hull is considered an excellent source of phenolic and antioxidant compounds It possesses a higher phenolic content (434–525 mg chlorogenic acid/100 g) and antioxidant properties compared to buckwheat groats; limited extraction studies have been reported on buckwheat hull [4,6,7,8]

Methods

Results

Conclusion