Review of Processing Methods of Jujube

Lianfang LI

Yunnan Industry & Trade Vocational College, Kunming 650300, China

Abstract Historical evolution of jujube processing, recording situation of modern processing specifications of jujube, research status of processing methods of jujube at home in recent years, content analysis of main chemical composition in jujube processed products, and impact of processing on chemical composition of jujube are reviewed, which could provide basic data for fully studying, developing and utilizing jujube by scholars and technical staff.

Key words Jujube, Processing method, Chemical constituents

1 Introduction

Jujubae Fructus is dry mature fruit ofZiziphusjujubaMill.[1], it is one of the traditional Chinese medicines with the same origin of medicine and food, and is listed as top grade in theDivineFarmer’sClassicofMateriaMedica. Jujubae Fructus is sweet in taste and warm in nature, and returns to the spleen, stomach and heart meridian[1]. It has the effects of invigorating spleen-stomach, replenishing Qi, nourishing blood, calming nerves, and alleviating drug properties, which is used for treating spleen deficiency, fatigue, loose stool, and Zang Zao of women. Jujubae Fructus has great prospects in development and application at home and abroad, and it is very necessary to conduct in-depth research and development.

There are many records on the processing methods of jujube in the ancient books of materia medica in the past dynasties, such as boiling, roasting, frying, steaming. There are also many records in modern monographs, but the processing methods that have been widely used are cleansing, cutting and drying. As traditional Chinese medicine for invigorating spleen-stomach, replenishing Qi, nourishing blood, calming nerves, and alleviating drug properties, the purpose of jujube processing is to make it more prominent in the treatment of diseases and stronger in the ability to ease drug properties. Therefore, it is of great significance to sort out and analyze the research data of jujube processing. By consulting ancient books and related literature monographs, historical evolution of jujube processing, modern processing technology and impact of processing on chemical constituents of jujube are analyzed, which could provide reference for formulation, modern research and clinical application of jujube processing technology.

2 Historical evolution of jujube processing

Jujube was firstly recorded in theBookofSongs, and it was called "Zao". In theDivineFarmer’sClassicofMateriaMedica, it is recorded that jujube is the top grade, and has the functions of "nourishing the spleen, helping the twelve meridians, calming the stomach Qi, dredging the nine orifices, replenishing less Qi, reducing body fluid, fusing hundreds of drugs, and prolonging life when taking it for a long time"[2].

Different processed products of jujube have been used earlier in the history of traditional Chinese medicine, and there are many processing methods, such as cleansing, cutting, steaming, frying, roasting, boiling, baking, charcoal making, burning, simmering, paste making, medicine juice making, crisp making and baking. Cleansing, cutting, frying, and steaming are the processing methods of jujube that have been used so far.

The earliest processing method of jujube recorded in ancient medical monographs was "breaking", which was recorded in theJinGuiYuHanJingof the Han Dynasty[3], and the specific processing method was to break it and remove the core. In theBencaojingJizhucreated by Tao Hongjing of the Liang Dynasty in Northern and Southern Dynasties, it was recorded as breaking[3]. In theBeijiQianjinYaoFangwritten by Sun Simiao in the Tang Dynasty, the processing method was ash burning[3]. In the Qianjin Yifang, the processing method was removing jujube kernel and peeling after steaming[3]. In theTaipingHolyPrescriptionsforUniversalReliefwritten by Wang Huaiyinetal.in the Northern Song Dynasty, it was recorded that jujube was tamped into pieces, and paper was used to wrap it tightly. It was burnt to red, and then it was taken out when cold[3]. In thePujiFangcompiled by Zhu Dietal.in the Ming Dynasty, it was recorded that jujube was removed kernel and peeled after cooking, and then it was mixed with the warm wine for baking[3]. In theCompendiumofPediatricscompiled by Chen Fuzheng in the Qing Dynasty, it was recorded as frying and grinding[3]. As can be seen from the above, there were many processing methods of jujube in ancient history. With the continuous progress of the times, its processing method is continuously improved and developed. Via literature research, it is found that among these processing methods, only steaming and frying have been used so far[4].

3 Recording situation of modern processing specifications of jujube

The recording situation of jujube by theChinesePharmacopoeiacontinued from 1963 to now. However, as for the records of jujube processing, any version only records the processing methods of cleansing, cutting and drying. In theChinesePharmacopoeiaof 2020, the processing of jujube only records the processing methods of cleansing, cutting and drying[1], namely removing impurities, washing, drying, breaking or nucleating when used. There are no records on other processing methods under jujube in any edition ofChinesePharmacopoeia. Even if in theExperienceIntegrationofChineseHerbalMedicineProcessing, processing methods of steaming and frying of jujube are only recorded[4]. In theChineseMateriaMedicacompiled by State Administration of Traditional Chinese Medicine in the 1990s, steaming of jujube is only recorded[5].

4 Research status of processing technology of jujube

For a long time, there are many scholars who have conducted in-depth research on the processing of jujube. Many scholars believe that the effect of jujube is better after processing. Wang Kezhou[6]studied four kinds of processing methods of jujube: cleansing, destructing jujube pericarp by external force, frying to yellow and sand scalding. He thought that the exocarp structure of jujube is dense, and there is a cuticle on the exocarp surface. When decocting jujube, it is difficult for the main components of jujube to enter the decoction through the exocarp. After the jujube pericarp is destroyed by external force, the drug’s utilization rate can be greatly improved, and the loss can be reduced. Therefore, it is considered that jujube should be used as medicine after processing. Li Lianfangetal.[12]compared seven processing methods of jujube: cleansing, frying to yellow, coke frying, charcoal frying, sand scalding, steaming and boiling. It was thought that the methods suitable for processing jujube included sand scalding, frying to yellow, cleansing, steaming, and boiling, while coke frying and charcoal frying were not suitable for processing jujube. Among them, sand scalding was an ideal processing method of jujube. The reason why the sand scalding method is ideal is that the finished product has good quality and high content of total flavonoids.

5 Content analysis of main chemical composition in processed products of jujube

Whether the processing technology of jujube is feasible or not needs to be verified, and the determination of index components is particularly important in verification process. The representative methods for the determination of main chemical components in jujube processed products in recent years are summarized in order to provide reference for relevant scholars studying the processing technology of jujube.

Jujube is rich in chemical constituents, containing alkaloids, saponins, flavonoids, polysaccharides, organic acids, amino acids and vitamins. At present, jujube mostly takes oleanolic acid as the index components of its quality control, and content is mostly determined by HPLC and spectrophotometry. There are also reports of rutin as an index component.

In theChinesePharmacopoeiaof 2020, oleanolic acid and betulinic acid are used as qualitative identification indexes for jujube processed products. Jujube is identified by TLC, and there is no record of jujube content determination.

According to below chromatographic conditions: acetonitrile∶methanol∶water (70∶16∶14) as mobile phase; 0.8 mL/min of flow velocity; 215 nm of detection wavelength; number of theoretical trays not less than 1 500 calculated by peak of oleanolic acid; 7.9 min of retention time; C18chromatographic column (TyPe waters, 4.6 mm×150 mm), Chen Jingetal.[7]used high performance liquid chromatography to determine the content of oleanolic acid in raw jujube. Because oleanolic acid was similar to ursolic acid in property, after test sample was extracted completely in diethyl ether, the loss of oleanolic acid was reduced using the method for dissolving chloroform, making that content determination of oleanolic acid in processed products had better accuracy. Meanwhile, the methodological study is stable and reproducible, so it could be used for quantitative analysis of oleanolic acid in processed jujube.

Xu Xiuyingetal.[8]used high performance liquid chromatography to determine rutin content in raw jujube. Chromatographic conditions were methanol∶0.05% H3PO4aqueous solution (42∶58) as mobile phase; 1.0 mL/min of flow velocity; 254 nm of detection wavelength; 25 ℃ of column temperature; number of theoretical trays not less than 2 500 according to the peak of rutin, 8.853 min of retention time; Phenomenex Luna C18chromatographic column (150 mm×4.6 mm, 5 μm of particle size). The method is simple and fast, with good linear relationship, which could be used for quantitative analysis of rutin in processed jujube.

Li Lianfangetal.[9]used ultraviolet spectrophotometry to determine content of total flavonoids in raw jujube, and this method was the first in the content determination of total flavonoids in jujube. Rutin was taken as control, and absorbance of total flavonoids in aluminum trichloride methanol solution was measured at the wavelength of 275 nm. The results displayed that content of total flavonoids in raw jujube was 0.41%, with high determination accuracy. Additionally, the method is stable and reproducible, which could be used for content analysis of total flavonoids in processed jujube.

6 Effects of processing on chemical constituents of jujube

Processing is traditional pharmaceutical technology of traditional Chinese medicine, and its processed products are the concentrated embodiment of the clinical effect of traditional Chinese medicine in the treatment of diseases. Via thousands of years of development, a unique processing theoretical system of traditional Chinese medicine has been formed. The processing of traditional Chinese medicine should follow the theoretical system of traditional Chinese medicine and the premise of inheriting the traditional processing technology of traditional Chinese medicine, and use methods and means of modern science and technology to standardize the traditional processing technology of traditional Chinese medicine decoction pieces and formulate quality standards of processed products, in order to provide a reliable guarantee for the clinical efficacy of traditional Chinese medicine decoction pieces in the treatment of diseases. The literature on impact of processing on chemical constituents of jujube in recent years is collected, which aims to provide reference for studying processing technology of jujube and making quality standard of jujube processed products.

Liu Shijunetal.[10]used high performance liquid chromatography to measure content of rutin in each processed product, such as frying to coke, frying to yellow, steaming with vinegar, roasting with vinegar, and three-steaming and three-making. It was found that after processing, content of rutin in each processing product of jujube was improved to different degrees. Among them, rutin content of jujube processed by wine steaming was the highest. It was thought that content of rutin in jujube could increase after processing, with certain significance in clinical use.

Liu Shijunetal.[11]used high performance liquid chromatography to detect content of cyclic adenosine monophosphate in the processed jujube, and compared raw jujube with processed one. The results displayed that the content of cyclic adenosine monophosphate was almost increased in steamed jujube with vinegar, roasted jujube with vinegar, steamed jujube with wine, roasted jujube with wine, jujube of three-steaming and three-making, fried jujube. Among them, content increase of cyclic adenosine monophosphate in jujube processed by vinegar steaming was the most. It is thought that the reason for the increase of cyclic adenosine monophosphate content after processing may be that water-soluble cyclic adenosine monophosphate can combine with vinegar and wine, and the dissolution of cyclic adenosine monophosphate is increased after steaming. The processing method of frying coke makes the epidermis of jujube with tight epidermis break after being fried by fire, which increases the internal heating area of jujube, and makes its effective components easier to overflow when heated. The experimental results showed that content of cyclic adenosine monophosphate in jujube after processing basically rose except raw jujube.

Li Lianfangetal.[12]used ultraviolet visible spectrophotometry to determine content of total flavonoids in processed jujube, and compared the content of total flavonoids in jujube processed by cleansing, frying to yellow, coke frying, charcoal frying, sand scalding, steaming and boiling. The results displayed that the deeper the heating degree of processed products, the higher the content of total flavonoids, namely fried charcoal products > fried coke products > sand scalding products > fried yellow products > boiled products > steamed products > cleansed products. By analyzing the maximum absorption wavelength of total flavonoids in each processed product in ultraviolet region and absorption peak spectrum, content of total flavonoids in sand scalding products was obtained, and accuracy of the determined results was higher. Content of total flavonoids and accuracy of determined results in fried coke and charcoal were lower, while accuracy of determination results of other three processed products was passable, but content of total flavonoids was obviously lower than sand scalding. It may be related to firepower and processing time during processing. The deeper the degree of heating during jujube processing, the more serious the destroy of total flavonoids. The results provide an important theoretical basis for the clinical application of jujube processed products in traditional Chinese medicine.

Liu Shijunetal.[13]studied the impact of sand scalding on main active components of jujube. They processed jujube by sand scalding, and determined the contents of main components of jujube (total triterpenoids, total flavonoids, total phenols and total alkaloids) before and after sand scalding by UV spectrophotometry. It was found that the contents of total triterpenoids, total flavonoids, total phenols and total alkaloids increased. Additionally, the overall effect of sand scalding after slicing jujube was better than that of the whole jujube. In the experiment, the increase of total alkaloids was particularly large, and the change trend of total components was obvious. It is clear that the contents of active ingredients in jujube after scalding are significantly increased, and its effect on treating diseases is improved compared with that of raw jujube. The research could provide certain basis for processed products of jujube by sand scalding in clinical application.

In conclusion, jujube, as a traditional Chinese medicine with the same origin of medicine and food, has a wide range of medicinal and development value. Historical evolution of jujube processing, collection of modern processing specifications of jujube, research status of jujube processing technology in China in recent years, content analysis of main chemical components in processed jujube products, effects of processing on chemical constituents of jujube are reviewed, which could provide basic data for scholars and technical staffs sufficiently studying, developing, and using jujube.