3.7.2. Determination of DPPH· Scavenging Capacity

We followed the method available in the literature with minor modifications to determine the scavenging capacity of DPPH [53]. For this, 0.3 mL of a specific concentration of the lower-phase solution and upper-phase solution was aspirated and mixed with 2.0 mL of DPPH· solution (0.1 mg/mL), making up to 10 mL with distilled water. The reaction was performed at room temperature for 30 min in the dark. The absorbance *A*<sup>1</sup> was measured at 517 nm. Next, 0.3 mL of the lower-phase solution and upper-phase solution was mixed with 2.0 mL of absolute ethanol, making up to 10 mL with distilled water. The reaction was performed at room temperature for 30 min in the dark and then the absorbance *A*<sup>2</sup> was measured at 517 nm. The curves depicting the scavenging rates of carbohydrates and polyphenols to DPPH· were drawn and IC<sup>50</sup> values were calculated. The same concentration of VC was used as a positive control.

$$\text{DPPH} \cdot \text{scavenging rate } (\%) = \left( 1 - \frac{A\_1 - A\_2}{A\_0} \right) \times 100\%$$

### 3.7.3. Determination of Fe3+-Reducing Power

The method available in the literature was followed with minor modifications to determine the reducing capacity of Fe3+ [54]. Further, 0.3 mL of the lower-phase solution or upper-phase solution, 2.5 mL of phosphate buffer solution (pH = 7.4), and 2.5 mL of 1% K<sup>3</sup> [Fe(CN)6] solution were mixed. The mixture was then placed in a water bath for 30 min at 50 ◦C. It was taken out and cooled to room temperature. Further, 1.0 mL of TCA was added, and the mixture was allowed to stand for 20 min before adding 2.5 mL of the supernatant, 0.5 mL of 0.1% FeCl3, and 2.5 mL of distilled water to it. The mixture was mixed well and left for 10 min. The absorbance was measured at 700 nm. The curves depicting Abs of carbohydrates and polyphenols were drawn, and IC<sup>50</sup> values were calculated. The same concentration of VC was used as a positive control.

### *3.8. High-Performance Liquid Chromatography Analysis*

### 3.8.1. Standard Solution Preparation

Appropriate masses of monosaccharides and uronic acid standards were accurately weighed and dissolved to prepare a 1 mg/mL mixed standard solution.

An appropriate mass of each phenolic acid standard was accurately weighed and dissolved to prepare a 0.2 mg/mL mixed standard solution.

### 3.8.2. Sample Solution Preparation

The lower-phase carbohydrate stock solution was freeze-dried as described in Section 3.2, and an appropriate mass of freeze-dried powder was weighed and dissolved to prepare the carbohydrate solution. To obtain the mixed standard solution and sample solution, 2 mL of 4 mol/L TFA solution was added to the carbohydrate solution and mixed well. The mixture was then hydrolyzed in an oven at 110 ◦C for 2 h, taken out, cooled to room temperature, and adjusted to neutral with 4 mol/L NaOH, making up to 5 mL with distilled water. We then took 200 µL of this hydrolyzed solution and added 200 µL of 0.3 mol/L NaOH solution and 200 µL of 0.5 mol/L PMP methanol solution and mixed the solution well. The solution was then placed in a water bath for 70 min at 70 ◦C. The solution was allowed to cool to room temperature. The pH of the solution was then adjusted by adding 200 µL of a 0.3 mol/L acetic acid solution and 200 µL of a 0.1 mol/L KH2PO<sup>4</sup> (pH = 6.0) solution. We then added 2 mL of CHCl<sup>4</sup> and vortexed the solution well to remove the chloroform phase. It was done thrice. The chromatographic analysis was performed on the solution after passing it through a 0.45-µm aqueous film.

The polyphenol solution was obtained using an appropriate volume of the upperphase stock solution prepared as described in Section 3.2.

### 3.8.3. Chromatographic Conditions

The high-performance liquid chromatography (HPLC) conditions of carbohydrates and polyphenols are listed in Supplementary Table S1.

### *3.9. Statistical Analyses*

Origin Pro 8 (OriginLab Corporation, Northampton, MA, USA) was used to analyze and map the experimental data, and Design-Expert 11 (Stat-Ease, Inc., Minneapolis, MN, USA) was used to design and analyze response surface experiments. IC<sup>50</sup> calculations were performed using Origin Pro 8 software.

### **4. Conclusions**

In this study, the powder mass, ammonium sulfate concentration, alcohol–water ratio, and ultrasonic time were considered the optimizing factors, and the optimum process conditions were obtained by constructing a double-response surface model: powder mass of 1.4 g, ammonium sulfate concentration of 0.34 g/mL, alcohol–water ratio of 0.4, and ultrasonic time of 43 min. Under these conditions, the polyphenol content in artichoke bud was 5.32 ± 0.13 mg/g and the polysaccharide content was 74.78 ± 0.11 mg/g. The HPLC spectrum analysis revealed that the carbohydrates in artichoke bud comprised mannose, rhamnose, glucuronic acid, galacturonic acid, glucose, galactose, and arabinose, with a molar ratio of 10.77:25.22:2.37:15.74:125.39:48.62:34.70. The polyphenols comprised chlorogenic acid, 4-dicaffeoylquinic acid, caffeic acid, 1,3-dicaffeoylqunic acid, isochlorogenic acid B, isochlorogenic acid A, cynarin, and isochlorogenic acid C, and the contents were 0.503, 0.029, 0.022, 0.017, 0.008, 0.162, 1.621, 0.030 mg/g, respectively. The antioxidant activity of ABTS<sup>+</sup> · and DPPH· scavenging and Fe3+-reducing abilities was determined in vitro. The results showed that the antioxidant activity of carbohydrates and polyphenols in artichoke bud was strong, and the antioxidant activity of polyphenols was stronger than those of carbohydrates.

In an aqueous two-phase system, the combination of ethanol and saline solution can be considered an environmentally friendly method for extracting biologically active substances. These mixtures are not only low-cost and simple to prepare but also provide a mild and nontoxic environment. In addition, replacing traditional solvents with an aqueous two-phase system has shown great benefits in extracting natural plant components, such as shorter extraction times and higher extraction efficiencies. Its use in combination with ultrasonic power provides a rapid and effective method to extract polyphenols and carbohydrates from artichoke bud. The optimal extraction process obtained by optimizing the dual-response surface model was stable and feasible, the carbohydrates and polyphenols

obtained by crude extraction had good antioxidative effects in vitro, and the material composition was obtained by HPLC analysis. These advantages provided a theoretical basis for exploring the biological activities of carbohydrates and polyphenols, and for resource development and utilization in more detail.

**Supplementary Materials:** The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/molecules27248962/s1, Table S1 HPLC conditions of carbohydrates and polyphenols; Figure S1 Influence of ultrasonic power (A), powder mass (B), extraction temperature (C), ultrasonic time (D), mass concentration of ammonium sulphate (E), and alcohol-towater ratio (F) on the extraction of carbohydrates and polyphenols from artichoke bud; Figure S2 In vitro antioxidant experimental evaluation of carbohydrates and polyphenols.

**Author Contributions:** Conceptualization, D.-S.Z.; methodology, X.L. and X.-K.L.; software, K.-H.Z., X.-Y.J.; investigation, X.L., K.-H.Z. and X.-K.L.; writing—original draft preparation, X.L. and X.-K.L.; writing—review and editing, D.-S.Z.; visualization, J.-C.C.; funding acquisition, P.-Z.Y. and D.-S.Z. All authors have read and agreed to the published version of the manuscript.

**Funding:** The authors thank the following funders: the Focus on Research and Development Plan in Shandong Province (2022TZXD0036), the National Natural Science Foundation of China (82004233), and the TCM Science and Technology Development Plan of Shandong Province (2019-0030).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data are contained within the article.

**Conflicts of Interest:** The authors declare no conflict of interest.

**Sample Availability:** Samples of the compounds chlorogenic acid, caffeic acid, isochlorogenic acid B, isochlorogenic acid A, cynarin, and isochlorogenic acid C are available from the authors.

### **References**

