Yield rate of the extracts of sorghum and
Abstract
Zein produced from maize is a hydrophobic protein, which holds great potential for a number of industrial applications, for example, food packaging, pharmaceutical, cosmetic, and biomedical industry. Sorghum, known as important cereal crop worldwide, is a good source of various phytochemicals such as tannins, phenolic acids, anthocyanins, phytosterols, and policosanols, and these phytochemicals have great impact on human health. Poria cocos, a well‐known traditional East‐Asian medicinal plant, is found around the roots of pine trees in Korea and China. As a rapid and efficient process, electrospinning has drawn huge interest among scientists to produce nanostructured polymer materials with excellent properties. In this work, we studied the influence of co‐solvent ratio and concentration of zein/medicinal plant extract on the morphologies of nanostructured zein/medicinal plant extract nanomaterials prepared by electrospinning technique from ethanol/water solution. The zein/medicinal extract nanofibers were characterized by field‐emission scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and differential scanning calorimetric technique. And we were to incorporate medicinal plant resources into the electro‐spun zein nanofibers by electrospinning technique to investigate the effect of medicinal extract on the morphologies, antibacterial, antioxidant, and other properties. Zein/medicinal plant extract might have a practical use as a new preservative for cosmeceutical applications.
Keywords
- natural polymer
- medicinal plant extract
- sorghum extract
- Poria cocos extract
- Electrospinning
- Nanofiber
- Cosmeceutical
- zein
1. Introduction
Recently, investigations have been focused on incorporating medicinal plant extracts with natural polymer‐based electro‐spun nanofibers due to their unique characteristics and applications. Such materials can be prepared by incorporating medicinal plant extract into the nanofibers of natural polymer by electrospinning technique. Electrospinning has generated great interest among scientists due to its very simple, low‐cost method to produce nanofiber which has exhibited outstanding properties such as high porosity and a high specific surface area [1–5]. Biomaterials are of huge interest to the scientists due to their inclusive potential applications particularly in tissue engineering and drug delivery [6–8]. Among the various types of biomaterials being developed, electro‐spun ultrafine fibers of protein‐based biomaterials are preferred for their cosmeceutical and medical applications. Having smaller pores and higher surface area than general fibers, electro‐spun fibers have been successfully used in different fields such as tissue engineering scaffolds, biomedical, pharmaceutical, healthcare, biotechnology, and others [9–13]. Medicinal plants act as a rich source for antimicrobial agents and used as drugs and cosmetics due to their medicinal properties [14–18].
The principle of electrospinning is simple; however, it is necessary to control the process as several variables have an influence on the properties of the end product [9, 19–22]. This chapter is concerned with the fabrication of natural polymer/medicinal plant extract electro‐spun nanofibers for cosmeceutical application which is one of the most important application areas. Furthermore, the effects of co‐solvent ratio and concentration of natural polymer/medicinal plant extract on the morphologies of nanostructured natural polymer/medicinal plant extract electro‐spun nanofibers were also investigated. The effectiveness of these bio‐nanofibers is demonstrated with a field emission scanning electron microscope (FE‐SEM), a transmission electron microscopy (TEM), thermogravimetric analysis (TGA), a differential scanning calorimetry (DSC) and the anti‐bacterial performance and antioxidant properties were also discussed.
2. Effect of co‐solvent ratios on the morphologies of electro‐spun zein/sorghum extract and zein/Poria cocos extract nanomaterials
Zein is considered as one of the best understood plant proteins and it is soluble in ethanol/water solution. It presents good cell compatibility and has more hydrophobic characteristics than other proteins as a result of the presence of polar amino acids, proline and glutamine, which are the major constituents of zein [23, 24]. As a biocompatible and biodegradable protein, zein has useful applications in tissue engineering and drug delivery [8, 23–26]. Also, zein has been extensively used in food packaging, cosmetic, pharmaceutical and biomedical industries [24, 27–32]. Another useful plant protein sorghum (
There are many parameters which have great influence on the morphology of the resultant electro‐spun materials varying from nanoparticles to nanofibers, having pores on their surface to beaded nanofibers. Electrospinning parameters can be broadly classified into polymer solution parameters and processing conditions that comprise the applied voltage, tip‐to‐collector distance (TCD), etc. In this work, we have studied the influence of co‐solvent ratio and concentration of zein/sorghum extract and zein/
2.1. Experimental
2.1.1. Materials
Zein (molecular weight = 35,000) extracted from corn was purchased from Tokyo Chemical Industry Co. Ltd., Japan. Sorghum was collected from National Institute of Crop Science (NICS) (Rural Development Administration, Korea).
2.1.2. Preparation of ethanolic extract and water extract of sorghum and Poria cocos
In case of ethanolic extract, at first, the stem and leaves of sorghum (
2.1.3. Preparation of spinning solution
Zein solutions were obtained by dissolving zein at different volume ratios of ethanol/water [9:1, 8:2, and 7:3 (v/v)] and various zein concentrations were used (10, 15, 20, 25, and 30 wt.%). Zein/sorghum extract blend solutions were prepared by dissolving various amounts of sorghum extracts in 7:3 (v/v) mixture solvent of EtOH/H2O at room temperature for 10 minutes. After that, 30 wt.% zein (based on the weight of the solution) was added into the above solution and the mixture was stirred for another 10 minutes. Following this similar method, zein/
2.1.4. Electrospinning
Zein solutions were carefully placed into a syringe and a syringe pump was used to deliver the solution through the blunt needle with a controlled solution feeding rate. Electrospinning was carried out under a constant electric field of 10 kV (Chungpa EMT Co., Korea), which was applied to the solution via an alligator clip attached to the syringe needle. An electrically grounded Al foil was used to collect fibers, which was placed at 15 cm vertical distance to the needle tip. Same method as described here was used for electrospinning zein/sorghum extract and zein/
2.1.5. Characterization
FE‐SEM images of the electro‐spun nanofibers of zein/
Figure 2 shows the variation in the FE‐SEM morphologies of the 10, 15, 20, 25, and 30 wt.% of zein electro‐spun nanofibers from the 7:3 (v/v) of ethanol/water co‐solvents. At a fixed applied voltage (10 kV) and TCD (15 cm), the effects of the polymer solution concentration on the morphology of zein nanofiber are illustrated. At low concentration of polymer solution (10 wt.% and 15 wt.%), mostly beads were produced as shown in Figures 2a and 2b. However, when the zein concentration was increased, fibrous products started getting formed and beads density decreased gradually (Figures 2c and 2d). Finally, uniform zein nanofiber mats having no bead defects were observed at 30% zein concentration (Figure 2e). Ultrafine zein electro‐spun nanofiber mats in a nanometer range (300–500 nm) prepared in the aqueous solutions are presented in Figure 2e. The key factors that control the formation of the beaded fibers are charge density carried by the jet, the viscoelasticity, and surface tension of the solution [21]. The effect of the different volume ratios of ethanol/water in the polymer solution was also evaluated by changing the ethanol content from 70% to 90% (v/v) and the results are presented in Figures 3 and 4. However, the most regular‐diameter ultrafine nanofibers were found at EtOH/water ratio of 70:30 and 30 wt.% zein concentration (Figure 2e).
FE‐SEM morphologies of electro‐spun zein nanofibers containing various quantities of sorghum (0, 5, 10, and 20 wt.%) and
The modified physical properties that developed in zein/sorghum extract solutions are responsible for these morphological changes [32]. An opposite trend was observed in case of zein/
2.2. Effect of extraction conditions on yield
Extract yield of sorghum and
Medicinal plant extracts | Total (g) | Yield rate (%) | |
---|---|---|---|
Water extract | Sorghum | 0.9468 | 1.1482 |
0.8259 | 0.9177 | ||
70 % EtOH extract | Sorghum | 1.5846 | 1.7414 |
1.3820 | 1.5356 |
3. Novel zein/medicinal plant extract electro‐spun nanofibers for cosmeceutical application
Due to biocompatible nature, bio‐nanofibers have superiority over their synthetic counterparts and have wide range of applications. Among the various types of bio‐nanofibers being developed, extensive efforts are currently being made for the development of protein‐based bio‐nanofibers. Nanofibers have a large surface‐to‐mass ratio that makes them promising candidates for advanced material devices [40]. A number of methods have been developed to spin nanofibers, among them electrospinning is one of the methods using electrical charge to draw nanoscale fibers from polymer liquid solutions [20, 41]. Natural nanofibers are preferred products over synthetic nanofibers as synthetic nanofibers are environmentally toxic [40].
The major purpose of this section is the incorporation of medicinal plant resources (sorghum extract and
3.1. Experimental
3.1.1. Materials
Zein (molecular weight = 35,000) extracted from corn was purchased from Tokyo Chemical Industry Co. Ltd., Japan. Sorghum was collected from National Institute of Crop Science (NICS) (Rural Development Administration, Korea).
3.1.2. Electrospinning
Zein/medicinal plant resources (sorghum extract and
3.1.3. Determination of antioxidant capacity
3.1.3.1. Free radical scavenging by the use of DPPH radical
The free radical scavenging activity was measured using DPPH radical following the protocols of Brand Williams modified by Miliauskas [44, 45]. Maximum absorption of DPPH radicals is at 515 nm and by an antioxidant compound, DPPH disappears with reduction. The DPPH solution in methanol (6 × 10‐5 M) was required to prepare daily and 3 ml of this solution was mixed with 100 μl of methanolic solutions of
where,
3.1.3.2. Free radical scavenging by the superoxide dismutase (SOD) assay
The superoxide anion scavenging activity of
3.1.4. Determination of anti‐microbial efficacy
For investigating anti‐bacterial performance of zein/medicinal plant extract,
3.1.5. Characterization
Average fiber diameters of the zein/
3.2. Results and discussion
3.2.1. Morphology
Figure 9 presents the dependence of the average diameters of the zein/sorghum and zein/
3.2.2. Thermal properties
Temperature | 50-150°C | 150-350°C | 350-450°C | Above 500°C | |
---|---|---|---|---|---|
Concentration | Dehydration and decomposition of the solvent |
Decomposition of the sorghum extract |
Decomposition of thezein |
Residue | |
Zein | Sorghum extract |
||||
30 wt.% | - | 92.12% | 34.17% | 20.25% | 18.51% |
30 wt.% | 5 wt.% | 92.94% | 34.62% | 21.81% | 19.35% |
30 wt.% | 10 wt.% | 93.49% | 38.15% | 26.48% | 24.64% |
30 wt.% | 20 wt.% | 94.87% | 43.65% | 30.03% | 27.72% |
To measure thermal properties of zein/sorghum extract and zein/
Temperature | 50-150°C | 150-350°C | 350-450°C | Above 500°C | |
---|---|---|---|---|---|
Concentration | Dehydration and decomposition of the solvent | Decomposition of the |
Decomposition of the zein | Residue | |
Zein | |||||
30 wt.% | - | 92.24% | 35.26% | 19.16% | 17.15% |
30 wt.% | 5 wt.% | 92.81% | 35.71% | 20.84% | 18.45% |
30 wt.% | 10 wt.% | 93.24% | 37.66% | 23.14% | 22.16% |
30 wt.% | 20 wt.% | 94.11% | 39.72% | 29.18% | 25.72% |
Zein/sorghum extract concentration | Tg (°C) |
---|---|
(a) 30 wt.% | 155.60 |
(b) 30 wt.%/5 wt.% | 159.32 |
(c) 30 wt.%/10 wt.% | 160.47 |
(d) 30 wt.%/20 wt.% | 166.77 |
The DSC data of electro‐spun zein nanofibers containing different sorghum extracts are shown in Table 4. The lowest glass transition temperature (155.60°C) and melting temperature were obtained from only zein nanofiber. Both glass transition temperature and melting temperature of zein/sorghum extract nanofibers were shifted towards higher temperature values with the higher weight percentage of sorghum extract. Similar effect was also observed when the
Zein/ |
Tg (°C) |
---|---|
(a) 30 wt.% | 155.60 |
(b) 30 wt.%/5 wt.% | 158.12 |
(c) 30 wt.%/10 wt.% | 159.48 |
(d) 30 wt.%/15 wt.% | 161.37 |
3.2.3. Antioxidant activities
Radical scavenging capacities of
Sample | Concentration (%) | Scavenging activity (%) |
---|---|---|
5 | 96.88 ± 0.91 | |
10 | 97.75 ± 1.42 | |
15 | 98.69 ± 1.49 |
Sample | Concentration (%) | SOD activity (%) |
---|---|---|
5 | 66.51 ± 6.45 | |
10 | 77.57 ± 4.34 | |
15 | 83.49 ± 5.73 |
Results obtained using SOD assay differed from those observed for DPPH assays. 15 wt.%
3.2.4. Anti‐bacterial ability
The anti‐microbial performance of zein and zein/sorghum extract nanocomposite against
On the other hand, zein/sorghum extract nanocomposites presented a remarkable decrease in the number of bacteria (Figure 11c, 11d, and 11e). These results recommended that only a small proportion of sorghum extract can make zein more competent against bacteria. The increase in the concentration of the sorghum extract stimulates decrease in the number of bacteria.
4. Conclusion
Different volume ratios (v/v) of ethanol/water solutions and zein concentration can affect the morphology of the electro‐spun zein nanofibers. Uniform zein nanofiber mats having average diameter around 600 nm could be obtained from the 7:3 (v/v) of ethanol with zein concentration of 30 wt.%. Different amounts of sorghum and
Acknowledgments
This research was supported by Technology Commercialization Support Program (113042‐3), Ministry of Agriculture, Food, and Rural Affairs. Also, this work was partially supported by Kyungpook National University Research Fund, 2015.
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