Green Extraction of Phenolic Compounds from Lotus Seedpod (Receptaculum Nelumbinis) Assisted by Ultrasound Coupled with Glycerol.

Nina Bao,Zisheng Luo,Guizhen Gao,Hujun Xie,Di Wang,Xizhe Fu

doi:10.3390/foods10020239

Nina Bao, Zisheng Luo + Show 4 more

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https://doi.org/10.3390/foods10020239

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Abstract

Lotus Receptaculum Nelumbinis has been sparking wide research interests due to its rich phenolic compounds. In the present work, ultrasonic-assisted extraction coupled with glycerol was employed to extract phenolic compounds from Receptaculum Nelumbinis and the process was optimized using a response surface methodology with Box-Behnken design (BBD). The optimal conditions for the total phenolic content (TPC) extract were obtained: glycerol concentration of 40%, an extraction temperature of 66 °C, ultrasonic time of 44 min, and the solvent-to-solid ratio of 55 mL/g. Under these optimum extraction conditions, the extraction yield of TPC was 92.84 ± 2.13 mg gallic acid equivalents (GAE) /g. Besides, the antioxidant activities demonstrated the ability of free radical scavenging by four different methods that included 2,2-Diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP), 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and reducing activity (RA) were 459.73 ± 7.07, 529.97 ± 7.30, 907.61 ± 20.28, and 983.66 ± 11.80 μmol TE/g, respectively. Six phenolic compounds were identified by ultra-high pressure liquid chromatography combined with triple-time-of-flight mass spectrophotometry (UPLC-Triple-TOF/MS) from the extracts. Meanwhile, Fourier transform infrared (FTIR) was conducted to identify the characteristic functional groups of the extracts and thus reflected the presence of polyphenols and flavonoids. Scanning electron microscopy (SEM) illustrated the microstructure difference of four treatments, which might explain the relationships between antioxidant activities and the structures of phenolic compounds.

Highlights

Lotus (Nelumbo nucifera Gaertn.) is a perennial freshwater plant widely cultivated in Asia and most parts are edible, so in China, they have been used for pharmaceutical purpose [1,2,3,4]
Lotus seedpod (LSP) has been reported to be rich in phenolic compounds, i.e., gallic acid, catechin, caffeic acid, quercetin, kaempferol, and possesses various physiological activities, such as antioxidant, antimicrobial, and anti-inflammatory, which make it interesting for incorporation as an important and valuable ingredient into the medicine, food, and cosmetics industry [6]
The glycerol concentration of 5–45% was chosen to evaluate the effect on the extraction yield of total phenolic content (TPC) (Figure 1A); 25–45% glycerol extracted more TPC, especially for 35% glycerol

Summary

Introduction

Lotus (Nelumbo nucifera Gaertn.) is a perennial freshwater plant widely cultivated in Asia and most parts are edible, so in China, they have been used for pharmaceutical purpose [1,2,3,4]. The extraction of phenolic compounds from different types of by-products in the food industry can attach more value to LSP and meets the concept of an eco-friendly economy [7]. Many innovative techniques have gained the interest of researchers in this area over the past years involving ultrasonic-assisted extraction (UAE), microwaveassisted extraction, solid-phase extraction, accelerated solvent extraction, and pressurized liquid extraction [10]. Among these techniques, UAE has been considered to be one of the most promising techniques due to its high efficiency, easy-handling, energy-saving and eco-friendliness, and easiness to scale-up for industry [11,12]

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