What Is the Benefit of Ginger Extract?

Ginger (Zingiber officinale Roscoe) belongs to the family Zingiberaceae, genus Zingiber [1], and is a perennial herbaceous monocotyledonous seed plant. Ginger is cultivated in a wide range of regions, from 18°14′ to 40°25′ north latitude, spanning the tropics, subtropics, and warm temperate zones, and is cultivated in all but cold highland areas [2].

In the past 20 years, China has replaced traditional ginger exporting countries such as India, Brazil, and Nigeria to become the leading ginger exporting country. Table 1 shows the data on China's ginger import and export from 1998 to 2007 retrieved from the United Nations data search system.

Ginger is cultivated in Guangdong and Zhejiang in the south of China, followed by Jiangxi, Anhui, Sichuan, Yunnan, Hunan, Hubei, etc.; in the north, Shandong is the main producing area, along with Henan, Shaanxi, etc. There are about 14 varieties cultivated in various parts of China: the variety grown in Jiaxing and Yuhang counties in Zhejiang is red-clawed ginger; the variety widely cultivated in Qianwei and Jiangyou counties in Sichuan is white ginger; the variety grown in Laifeng County in Hubei is Laifeng ginger; and Shandong Laiwu, Teng County, Tai'an and Jiaodong area are the main producing areas of northern ginger[3].

Ginger rhizomes are nutrient-rich, with a dry matter content of 13.2%–15.5%, total lipids 5.7%–14.5%, total soluble sugars 2.02%–5.345%, cellulose 5.23%–5.95%, crude protein 7.98%–10.04%, and starch 5.78%–8.88%. per 500g of fresh ginger contains 9.18 to 16.7 mg of vitamin C. Starch is the most abundant, accounting for 40% to 60% of the weight of dried ginger [4].

1 Ginger extract extraction methods [5-8]

At present, after many experts' research, the ginger extract extraction process has become relatively mature. The main methods include water steam distillation, solvent extraction, cold pressing, supercritical CO2 extraction, molecular distillation, etc. According to the processing methods and the different components contained, two deep processing products are obtained: ginger essential oil and ginger oleoresin.

2 Research on the composition of ginger extract

Ginger is an important spice worldwide and a traditional medicinal and edible plant in Asia [9]. Ginger has a complex chemical composition, with more than 100 different compounds having been identified. It can be divided into three main categories: volatile oil, gingerol and diphenylheptane [10]. In addition, it contains a variety of amino acids, vitamins and trace elements such as iron, copper, manganese, zinc, chromium, nickel, cobalt and germanium, as well as a variety of functional ingredients. Ginger extract mainly consists of ginger oil, ginger oleoresin and other functional ingredients.

2.1 Ginger oil

Ginger oil is mainly composed of volatile components in ginger, which determine the aroma and flavor of ginger. American perfumers evaluate ginger oil as follows: aroma characteristics (2%): woody, ginger, citral, sweet, spicy, camphor, terpene, earthy; taste characteristics (30×10-6): ginger, spicy, woody, citrus. Ginger oil is not only widely used in food, but also in medicine, daily cosmetics and spices.

Ginger oil is extracted from fresh ginger roots or dried ginger. The most obvious difference between the two is the content of citral, which is lower in essential oil extracted from dried ginger [11]. The main components of ginger oil mentioned in the literature [12–17] are shown in Table 2. The chemical composition of ginger oil is mainly terpenoids, of which sesquiterpene hydrocarbons have the highest content, followed by oxidised sesquiterpenes. The others are mainly monoterpene hydrocarbons and oxidised monoterpenes. The oxygen-containing derivatives of monoterpenes and sesquiterpenes are mostly highly aromatic and biologically active, and are important raw materials for the pharmaceutical, food, fragrance and cosmetics industries.

The composition of ginger oil produced by different varieties of ginger from different regions also differs, as shown in Table 3.

2.2 Ginger oleoresin

Ginger oleoresin is a relatively viscous semi-fluid substance that mainly contains volatile components and non-volatile components that are soluble in the extraction solvent. Its content of gingerol determines the spicy flavor of ginger [20]. Ginger oleoresin is mainly extracted by solvent extraction. The solvents used to extract ginger oil mainly include ethanol, acetone, trichloroethane and dichloroethane [21], of which the latter two are carcinogenic.

The gingerol component in ginger is not only the main flavoring substance responsible for the characteristic ginger flavor, but also the main functional factor responsible for ginger's various pharmacological effects. The gingerols in gingerol are chemically unstable and tend to lose water or undergo reverse aldol condensation reactions to form gingerone and corresponding aliphatic aldehydes when heated or treated with acids or alkalis. Gingerol is a mixture of various substances, all of which contain the functional group 3-methoxy-4-hydroxyphenyl in their structure. Gingerol is divided into seven categories according to the different fatty chains attached to this functional group [23,24]: gingerols, shogaols, xanthones, xanthones, diacetyl, diacetyl, and others, as shown in Figure 1.

2.3 Other functional compounds in ginger

Diarylheptanoids are a general term for a class of compounds with 1,7-disubstituted phenyl groups and a heptane backbone as the parent structure. They can be divided into linear diarylheptanoids and cyclic diarylheptanoids. Kikuzaki et al. carried out relatively systematic and in-depth work on the isolation and identification of antioxidant activity of ginger compounds. They first isolated 5 types of 13 linear diphenylheptane compounds in 1991 [25,26], see Figure 2. These compounds have antioxidant activity. In 1996, they isolated 2 types of 5 new cyclic diphenylheptane compounds from the dichloromethane of ginger [27], see Figure 3.

Chinese scientists Yu et al. discovered two new compounds from ginger in 2007, see Figure 4, one of which is a cyclic diphenylheptane compound. These two compounds also have antioxidant activity [28].

Tao Chen, Yang Xiaosheng, et al. [29] extracted 28-tetracosane, 30-tetracosane, 16-cetyl glyceride, β-elemene acetate, β-sitosterol and other 5 compounds from the pressed ginger juice, see Figure 5. These compounds were all isolated from the plant for the first time, and are of certain value for the pharmacology and toxicology of medicinal ginger and the development of new drugs.

3 Modern scientific research on the functionality of ginger

Traditional Chinese medicine ginger is pungent and warm in nature, with warming, invigorating, perspiring, antiemetic, and detoxifying effects. It is used to treat external colds, headaches, phlegm, coughs, stomach colds, and vomiting; it also improves blood circulation and dispels cold evil [30]. Ginger extract contains a very high level of antioxidants, which can be used as a free radical scavenger, with anti-mutagenic and anti-inflammatory effects.

3.1 Ginger for the treatment of nausea and vomiting

Ginger has long been used to cure nausea and vomiting in some cases. Ginger extract is very effective in the treatment of motion sickness and slow stomach caused by rotation [31]. Eva Bryer, C NM, in a 2005 review of previous research papers, mentioned that ginger is effective in suppressing nausea and vomiting during pregnancy in 80% of pregnant women [32]. Chemotherapy for cancer can cause severe nausea, vomiting and stomach discomfort in patients. The results of 41 white blood cell patients treated with ginger or placebo showed that ginger was significantly more effective than placebo users [33].

3.2 Anti-inflammatory activity of ginger

Ginger oil can significantly inhibit xylene-induced ear swelling in mice and egg white-induced foot swelling in rats, indicating that ginger oil has a significant anti-inflammatory effect on acute inflammation [34]; ginger oil can also inhibit the formation of granulomas in mice, suggesting that ginger oil has an antagonistic effect on chronic inflammation; ginger oil can reduce the ear swelling caused by dinitrochlorobenzene (DNCB) in mice with delayed hypersensitivity, significantly reduced thymus and spleen indices, and inhibited T cell-dependent delayed-type hypersensitivity. Ginger extract can inhibit the synthesis of leukotrienes by inhibiting both cyclooxygenase and lipoxygenase [35].

3.3 Research on ginger for cancer treatment

Yogeshwer et al. [36] reviewed articles on the anti-cancer effects of ginger in 2006. The review states that the gingerol components in ginger and other ginger varieties have antioxidant and free radical scavenging effects and prevent cancer. The main anti-cancer components in ginger come from the gingerol components in ginger, such as [6]-gingerol and [6]-shogaol, as well as some other components such as shogaone and shogaols.

3.4 Other functions of ginger

Ginger has a certain effect on cardiovascular disease. Gingerol can affect Ca2+-ATPase in dog heart tissue and rabbit skeletal muscle, thereby activating the sarcoplasmic reticulum (SR) of cardiac muscle and skeletal muscle fibers [37]. In addition, ginger has an effect on blood lipids and glucose, blood pressure, and blood clotting.

Water-ethanol extracts of ginger can activate serum transaminase and alkaline phosphatase to prevent liver toxicity. They have a hepatoprotective effect because they can prevent the concentration of liver antioxidants from decreasing to prevent acetaminophen-induced acute toxicity, or because they have the ability to directly scavenge free radicals [38].

4 Conclusion

Ginger and its extracts have medicinal and health-promoting functions such as anti-ulcer, antibacterial, anti-inflammatory, antioxidant, anti-aging, lowering blood pressure, and treating cardiovascular and cerebrovascular diseases. It is meaningful to identify the active ingredients in ginger and its extracts. Different varieties of ginger have different contents of active substances, which provides guidance for ginger breeding and cultivation. The identification of these active ingredients can promote the further development and application of ginger.

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