Comparison of Different Processing Methods of Ziziphus jujuba Mill.

Lianfang LI

Yunnan Industry & Trade Vocational College, Kunming 650300, China

Abstract [Objectives] To study and compare the processing methods of Ziziphus jujuba Mill. [Methods] Z. jujuba was processed by seven methods: cleaning, yellowish frying, burnt frying, carbonized frying, moistening by hot sand, steaming, and boiling. Ultraviolet-visible spectrophotometry was used to determine the content of total flavonoids in each processed Z. jujuba. [Results] The content of total flavonoids measured by various processing methods was different. The content of total flavonoids in the processed Z. jujuba by moistening by hot sand was relatively high and the absorption peak spectrum was almost the same as that of the cleaned processed Z. jujuba and the rutin reference substance. [Conclusions] The moistening by hot sand is the optimal method for processing of Z. jujuba.

Key words Ziziphus jujuba Mill., Processing of traditional Chinese medicine, Total flavonoids, Ultraviolet-visible spectrophotometry

1 Introduction

Jujubae Fructus is dried ripe fruit ofZiziphusjujubaMill., a plant ofZiziphusgenus in Rhamnaceae family. It is a commonly used traditional Chinese medicine and listed as premium medicinal product inDivineFarmers’ClassicofMateriaMedica.Z.jujubais sweet in taste, warm in nature, and belongs to the spleen and stomach meridians. It is a commonly used traditional Chinese medicine for reinforcing middle-warmer and replenishing qi, nourishing blood and tranquilization, and moderating the properties of herbs. It is used for spleen deficiency, lack of food, fatigue, loose stools, hysteria of women,etc. It has broad application prospects both at home and abroad. In the past,Z.jujubahad many processing methods, mainly including cleaning, slicing, making paste, steaming, burning, roasting in ashes, concoction processing, crisp making, baking, boiling, wine processing, stir-frying,etc. Now, the main processing methods ofZ.jujubaare cleaning, slicing, steaming, and stir-frying.

The earliest processing method ofZ.jujubais called "Bo" (splitting or slicing in Chinese), initially recorded inTheCanonoftheGoldenCofferandJadeSheath(Jingui Yuhan Jing)[1]in the Han Dynasty. This process is to remove the kernel ofZ.jujuba. In the Liang Dynasty, theCollectiveNotestotheCanonofMateriaMedicarecorded the processing of Bopo (splitting to break)[1]. In the Tang Dynasty, theEssentialFormulasforEmergenciesWorthaThousandPiecesofGold(Beiji Qianjin Yaofang)[1]made a record of the processing of burning in ashes. Also in the Tang Dynasty, theWingsoftheThousandGoldPiecesFormulary(Qianjin Yifang)[1]made a record of the processing of removing the kernel and steaming to peel. In the Song Dynasty, thePeacefulHolyBenevolentPrescriptions(Taiping Shenghui Fang) had the following records: pound into pieces, wrap tightly in paper, burn to red, and take it out when it is cooled down[1]. In the Ming Dynasty, thePrescriptionsforUniversalRelief(Puji Fang) had the following records: boiled, remove the kernel and peel, and mix with warm and wine, and dry by roasting[1]. In the Qing Dynaasty, theCompleteWorkonChildren’sDiseases[1](Youyou Jicheng) made a record of stir-frying and grinding. In the past, there have been many processing methods forZ.jujuba. With the progress of the times, the processing methods have been continuously improved and developed. Steaming and stir-frying have been used to this day. The processing specifications ofIntegrationofTraditionalChineseMedicineProcessingExperience[2]include the processing methods of steaming and stir-frying ofZ.jujuba. In theChineseMateriaMedica, there are records of the processing method ofZ.jujuba: take theZ.jujubaand wash it, put it in a steamer, heat and steam for half an hour, take it out, and dry it[3]. However, in theChinesePharmacopoeia(2015), there are only records of cleaning, cutting, and frying processing ofZ.jujuba, no other methods.

In the past 20 years, some scholars have made an in-depth research on the processing ofZ.jujuba, and it is agreed that the decoction rate ofZ.jujubaafter processing is higher and the effect is better. Wang Kezhou[5]studied the method ofZ.jujubaprocessing and believed that after external force destroys theZ.jujubapeel, yellowish frying, and moistening by hot sand, it will help the water-soluble components ofZ.jujubato enter the decoction to the maximum, thereby improving the drug utilization rate. However, there is still no comprehensive comparison of cleaning, cutting, steaming, and stir-frying processing methods that are still used at present. Flavonoids are one of the chemical components ofZ.jujuba.Z.jujubais rich in a variety of flavonoids, such as rutin, quercetin, and flavonoids. These flavonoids have pharmacological activities such as vasodilation and anti-oxidation. In this study, we compared the content of total flavonoids inZ.jujubaprocessed by methods of cleaning, yellowish frying, burnt frying, carbonized frying, moistening by hot sand, steaming, and boiling, and determined the optimal processing method.

2 Materials

2.1 Source of raw materials and reagentsTheZ.jujubawas provided by Yunnan Jinfa Pharmaceutical Co., Ltd., and was identified as the dried ripe fruit ofZiziphusjujubaMill. by the quality department of the company; the rutin reference substance (batch No.HL-180122, purity ≥ 98%, purchased from China Food and Drug Control Research Institute); distilled water; other reagents used in the experiment were of analytical grade, purchased from Zhuoda Instrumentation Business Department, Guandu District, Kunming.

2.2 InstrumentsUV-1800PC-DS Ultraviolet-Visible Spectrophotometer (Shanghai Mapada Instruments Co.,Ltd.); LAC-224C Electronic Analytical Balance (Changshu Menglan Braun Balance Instrument Co., Ltd.); DK-98-IIA Water Bath; Reflux Extractor (Tianjin Tianbo Glass Instruments Co., Ltd.); JCZ-(Y)-M Integrated Stove (Zhongshan Meichui Electric Appliance Co., Ltd.); BWS-30-SX Electronic Balance (Shenzhen Baishite Electronics Co., Ltd.); herbal medicine roasting pot, herbal medicine frying spade, bamboo weaving, porcelain plate,etc. are purchased from Zhuoda Instrumentation Business Department, Guandu District, Kunming.

3 Methods and results

3.1 Processing methods ofZ.jujuba

3.1.1Cleaning. Remove impurities, wash and dry. Cut into pieces or remove the kernel when using[4].

3.1.2Yellowish frying. Take the cleanZ.jujuba(the kernel is removed, cut into two pieces, the same size), placed in the pre-heated frying container, heated using medium fire, and fry until the color is darkened and the inherent smell is released, then take out, spread out, and cool down. Sieve to remove debris.

3.1.3Burnt frying. Take the cleanZ.jujuba(the kernel is removed, cut into two pieces, the same size), placed in the pre-heated frying container, heated using medium fire, and fry until the color is burnt brown on the surface and burnt yellow inside and the burnt aroma is released, then take out, spread out, and cool down. Sieve to remove debris.

3.1.4Carbonized frying. Take the cleanZ.jujuba(the kernel is removed, cut into two pieces, the same size), placed in the pre-heated frying container, heated using strong fire, and fry until the color is burnt black on the surface and burnt yellow inside, then take it out, spread it out, and cool down. Sieve to remove debris.

3.1.5Moistening by hot sand. Take the river sand (at the amount that can covers the medicine) and place it in a frying container, heat with strong fire, and fry it until the river sand is in a loose state,put into the cleanZ.jujuba(the kernel is removed, cut into two pieces, the same size), continuously stir-fry to the state of bulging, take out and spread out, sieve to remove the river sand, and cool down.

3.1.6Steaming. Take the cleanZ.jujuba(the kernel is removed, cut into two pieces, the same size), placed in the steaming container, steam over the water for half an hour (first strong fire then soft or mild fire, when steaming, start timing), take out and spread out, cool down, and dry.

3.1.7Boiling. Take the cleanZ.jujuba(the kernel is removed, cut into two pieces, the same size), placed in the boiling container, add water and boil half an hour (at the amount of water that is just above the medicine level; use strong fire first then soft or mild fire, when boiling, start timing), till the water is absorbed completely by the medicine, take out and spread out, cool down, and dry.

3.2 Comparison of properties of finished products processed by different methodsTake the finished products obtained by various processing methods in Section3.1and place them in a porcelain plate, and observe and compare the properties of theZ.jujubapieces in terms of shape, size, color, surface characteristics, and texture characteristics (Fig.1).

Note: A-F are yellowish fried, burnt fried, carbonized fried, moistened by hot sand, steamed, and boiled products.Fig.1 Properties of finished Ziziphus jujuba Mill. processed by different methods

Through comparing the properties of various processed products, there is almost no difference in the shape, size, and texture characteristics of various processed products, but the color and surface characteristics are quite different. Among them, burnt products and carbonized fried products have the most significant changes. From the appearance point of view, the properties of burnt products and carbonized fried products are likely to have changed. In order to fully verify which processing method is the optimal processing method forZ.jujuba, we conducted the following tests.

3.3 UV determination of processedZ.jujuba

3.3.1Preparation of standard solution. Precisely weighed 10 mg of the rutin reference substance, dissolved it with methanol, and diluted the methanol into a 50-mL volumetric flask.

3.3.2Plotting of standard curve. Separately pipetted 0, 0.5, 0.75, 1.0, 1.25, 1.5, 1.75, 2.0 mL of standard solution to a 25-mL volumetric flask, added 1 mL of 2% AlCl3solution to each solution, shook up, diluted to the desired volume with methanol, and let it stand for 30 min after well mixing. Added the standard solution to prepare a blank solution in the same way, and measured the absorbance value. Made a record of the absorbance value of the series of standard solutions in the standard solution measurement section, and plotted the standard curve with the concentration (C) as the abscissa and the absorbance value (A) as the ordinate. The regression equation was obtained:Y=0.041 7X+0.002 7,r=0.999 9. Results indicated that the detection concentration of rutin has a good linear relationship with absorbance in the range of 4.96-19.84 μg/mL.

3.3.3Preparation of sample solution. Took an appropriate amount of each processed product (dried for 7 h at 60 ℃), pulverized, took about 1 g of each processed product powder, added 20 mL of 60% ethanol, weighed, reflux extracted for 2 h, sealed the conical flask and cooled down, made up the loss weight with 60% ethanol, heated in water bath, filtered while it was still hot, and took the additional filtrate as the sample solution.

3.4 Comparison of absorption spectra of total flavonoids and rutin in processed productsTook eight 25-mL volumetric flasks, added 1 mL cleaned product sample solution for No.1, added 0.5 mL yellowish fried, moistened by hot sand, steamed, and boiled product sample solutions for No.2, 3, 4, and 5, and added 0.2 mL burnt fried and carbonized fried products for No.6 and No.7, respectively. Added 1 mL of rutin standard solution (0.248 mg/mL) to the No.8 flask, add 1 mL of 2% AlCl3solution to each volumetric flask, and shook well. All 8 volumetric flasks were diluted to the desired volume with methanol. After well mixing, let them stand for 30 min and placed in a 1-cm quartz cuvette, prepared the blank solution with 1 mL of 2% AlCl3solution in the same way, and used an ultraviolet-visible spectrophotometer to scan the entire wavelength range from 200 to 800 nm. The maximum absorption wavelength of each processed product is indicated in Table 1, and the absorption peak spectrum is shown in Fig.2.

From Table 1 and Fig.2, it can be seen that in the ultraviolet region, the maximum absorption wavelength of the rutin reference substance is 275 nm, and the maximum absorption wavelengths of the total flavonoids of the cleaned product and the steamed product are 275 and 274 nm, respectively, which are almost consistent with the maximum absorption peaks of the rutin reference substance. The maximum absorption wavelengths of the total flavonoids of yellowish fried products, moistened by hot sand products, and boiled products are 282, 280, and 280 nm, respectively, and the absorption peaks were slightly red-shifted. We compared the absorbance near the peak of the total flavonoids of each processed product. There was little difference in absorbance between 275 and 282 nm, and the difference was in the range of 0.005-0.001. The maximum absorption wavelength of the total flavonoids of burnt fried and carbonized fried products were not displayed. From the spectrum, the peaks of the total flavonoids of the two were absent. Therefore, according to the analysis on absorption peak spectrum of the total flavonoids of each processed product, we can know that the cleaning, steaming, yellowish frying, moistening by hot sand and boiling methods are all suitable for processingZ.jujuba, while the burnt frying and carbonized frying methods are not suitable for processingZ.jujuba, which may be related to the degree of heat ofZ.jujubaduring processing. The higher the degree of heat ofZ.jujuba, the more serious the damage to the total flavonoids ofZ.jujuba.

Fig.2 Absorption peak spectrum of total flavonoids in processed Ziziphus jujuba Mill. and rutin

3.5 Determination of total flavonoids in processed products

Precisely weighed 1 mL of sample solution of cleanedZ.jujubain Section3.2.3, and 0.5 mL of sample solution of yellowish fried, moistened by hot sand, steamed, and boiledZ.jujuba, and 0.2 mL of sample solution of burnt fried and carbonized friedZ.jujuba, to a 25-mL volumetric flask. Prepared the sample test solution using the method in the section of the standard curve, took the supernatant that has been allowed to stand for 30 min to determine the absorbance, and calculated the concentration of total flavonoids in the diluted solution from the regression equation, and then calculated the percentage of total flavonoids in each processed product, and the results are shown in Table 2.

As shown in Table 2, the deeper the heat of the processed product, the higher the content of total flavonoids, namely, carbonized fried > burnt fried > moistened by hot sand > yellowish fried > boiled > steamed > cleaned. However, according to theRSDvalues, theRSDvalues of burnt fried and carbonized fried products are larger, and the accuracy of the measurement results is lower, which is possibly related to the greater the fire and the deeper the processing degree during processing, and the more difficult it is to judge the consistency of the fire temperature by naked eyes. The content of total flavonoids in products moistened by hot sand was 1.552%, which is higher, and theRSDvalue was 0.74%, the measurement result is more accurate, so it is an ideal processing method forZ.jujuba.

Table 2 Content of total flavonoids in processed Ziziphus jujuba Mill.

4 Conclusions

According to the analysis on absorption peak spectrum of the total flavonoids of each processed product, it can be concluded that the cleaning, steaming, yellowish frying, moistening by hot sand and boiling methods are all suitable for processingZ.jujuba, while the burnt frying and carbonized frying methods are not suitable for processingZ.jujuba, which may be related to the degree of heat ofZ.jujubaduring processing. The higher the degree of heat ofZ.jujuba, the more serious the damage to the total flavonoids ofZ.jujuba.

Besides, according to the analysis results of the content of the total flavonoids in processedZ.jujubaproducts, the deeper the heat of the processed product, the higher the content of total flavonoids, namely, carbonized fried > burnt fried > moistened by hot sand > yellowish fried > boiled > steamed > cleaned. However, according to theRSDvalues, theRSDvalues of burnt fried and carbonized fried products are larger, and the accuracy of the measurement results is lower, which is possibly related to the greater the fire and the deeper the processing degree during processing, and the more difficult it is to judge the consistency of the fire temperature by naked eyes. The content of total flavonoids in products moistened by hot sand and the measurement results are more accurate.

In conclusion, the method of moistening by hot sand is an optimal method for processing ofZ.jujuba. These results are expected to provide an important theoretical basis for the clinical application of processedZ.jujubaproducts in traditional Chinese medicine, and are of great significance to the research and development ofZ.jujubaready-to-eat decoction pieces.

This paper is the translation of the Comparison of Different Processing Methods ofZiziphusjujubaMill. already published in theChineseJournalofEthnomedicineandEthnopharmacy(CN: 53-1102/R; ISSN:1007-8517).