2.1. The Ginsenoside Contents of NZ-Grown Ginseng
In this study, the amount of 21 ginsenosides in 10 batches of ginseng samples were analyzed using LC-MS/MS described in our previous method [11
]. Briefly, thirteen ginsenosides (Rb1, Rb2, Rb3, Rc, Rd, Re, Rf, Rg1, Rg2, Rg3, Rh1, Rh2, and F2) were accurately quantified by their own linear regression equations of standard curves, and some ginsenosides without reference standards, such as ginsenosides m-Rb1 (m = malonyl), m-Rb2, m-Rb3, m-Rc, m-Rd, m-Re, and m-Rg1, were relatively quantified by the regression equations of their corresponding neutral ginsenosides. As shown in Table 1
, apart from the individual ginsenoside content, the total ginsenoside amount, the ratio of protopanaxadiol (PPD)-type to protopanaxatriol (PPT)-type (PPD/PPT) and the ratio of neutral ginsenoside to malonyl ginsenoside (G/m-G) are also described in this section.
Among those samples, the ginsenoside concentrations were varied. The highest amount (102.69 ± 0.91 mg/g) and the lowest amount (38.72 ± 0.15 mg/g) were from the third batch and fifth batch of samples, respectively. Ginsenosides Rg1, Rb1, m-Rb1, and Re are the four major ginsenosides in most samples except the fourth and fifth batches of samples, while in the fourth and fifth batches of samples, the major ginsenosides give way to the ginsenosides m-Rb1, m-Rb2, m-Rc, and Rg1 based on their concentrations. The high amount of m-Rb1, m-Rb2, and m-Rb3 lead to the higher ratios of PPD/PPT and lower ratios of G/m-G in sample four and five. Both ratios are approximately two from other samples.
Usually, ginseng refers to the whole ginseng root including the main root body, root hair, and rhizome. In our previous study, we analyzed ginsenosides from different parts including main root, fine root, rhizome, stem, and leaf [11
], it was found that the underground parts, including main root, fine root, and rhizome, have very similar ginsenoside composition. In this study ginsenosides were determined from the whole underground part. There is another study reporting ginsenosides analysis for NZ-grown ginseng [12
], which only detected seven main ginsenosides in four batches of ginseng samples. In order to compare with China and Korea grown ginseng, the data from Table 1
and Follett’s publication [12
] are used to calculate the average content of ginsenosides of NZ-grown ginseng.
2.2. The Average Content of Ginsenosides in Different Regions
In order to obtain the average content of ginsenosides from China grown ginseng and Korea grown ginseng, we searched the scientific literature for ginsenosides analysis from ginseng grown in China and Korea. A total of 524 articles were located, and 151 potentially relevant studies were selected to full-text review after removing the duplicates (N = 230), abstract only (N = 13) and screening on the basis of title and abstract according to the inclusion criteria. After exclusion of 102 articles for the reasons given in Figure 2
, we included 49 articles (article lists are supplied in the Supplementary Materials
). Among these articles, 30 articles were about ginsenosides analysis for China grown ginseng, 17 for Korea grown ginseng, and two for NZ-grown ginseng.
After extracting the data from the inclusion articles, the amount of ginsenosides from 113 batches of China grown ginseng roots aged from three to 30-years old was used to calculate the average content of ginsenosides of China grown ginseng. A total of 106 batches of Korea grown ginseng roots with different ages (one to 10-years old) were analyzed from 17 publications. For NZ-grown ginseng, there were 14 batches of samples tests, including ten batches of ginseng roots in this study and four from the literature.
As shown in Figure 3
, the average content of total ginsenosides from NZ-grown ginseng (40.06 ± 3.21 mg/g, n = 14) is significantly (p
< 0.05) 1.4 times higher than that of China grown ginseng (16.48 ± 1.24 mg/g, n = 113) and 90% higher compared with that of Korea grown ginseng (21.05 ± 1.57 mg/g, n = 106). There is no significant difference in the average content of total ginsenosides for ginseng grown in China and Korea.
The average contents of seven individual ginsenosides are shown in Figure 4
, the average concentrations of ginsenoside Rb1, Re, Rf, and Rg1 from NZ-grown ginseng are significantly (p
< 0.05) 2.22, 2.91, 1.65, and 1.27 times higher than that of China grown ginseng, respectively. The ginsenosides Re, Rf, and Rg1 of New Zealand ginseng are 3.14, 1.55, and 2.63 times that of Korean ginseng, respectively. The average content of PPD type ginsenosides Rb2, Rc, and Rd are not significantly different among the three growing regions of ginseng.
It is reported that the ratios of PPD to PPT and Rb1 to Rg1 are less than 2.0 and less than 5.0 in Panax ginseng
, respectively [13
]. Thus, we also calculated these ratios of ginsenosides from three countries (Figure 5
). The PPD/PPT ratios of all the NZ-grown ginsengs are less than 2.0, although the average ratio of PPD/PPT from China grown ginseng is less than 2.0, many of the ratios are more than 2.0. While, most values of PPD/PPT from Korea grown ginseng are more than 2.0, leading to the average with >2.0. Although the average ratios of Rb1/Rg1 are less than 5.0 among three countries, some ginseng samples still have Rb1/Rg1 > 5.0. In addition, the ratios of Rg1 to Re is more than 1.0, and the ratio of Rb2 to Rc is more than 0.4 in Panax ginseng
]. From the average level, the average ratios of Rg1/Re and Rb2/Rc are more than 1.0 and 0.4, respectively, among the three regions’ ginseng samples. However, neither the value of Rg1/Re stays >1.0 all the time, nor the value of Rb2/Rc shows >0.4 in all samples.
Since the contents of PPT type ginsenosides (Re, Rf and Rg1) in NZ-grown ginseng are significantly higher than that of Chinese ginseng and Korean ginseng, besides Rb1, the concentrations of other PPD type ginsenosides (Rb1, Rc and Rd) have no significant difference among three regions’ ginseng, which lead to the lower PPD/PPT ratio in NZ-grown ginseng.
As the two most important sources of ginseng production, the total production by China and Korea is 72,229 tons, which was approximately 90.2% of the world ginseng production [15
]. Many studies have reported the ginsenoside concentrations from China and Korea. However, they mainly focused on one batch or limited batches of sample analysis [16
]. There are few studies concerning the comparison of ginsenosides between ginseng grown in different countries. We did not know if they have some differences in the ginsenosides content between China and Korea grown ginseng. In this study, the average content of ginsenosides from hundreds of batches of ginseng samples represent the ginsenoside levels of ginseng grown in different regions. We can see there is neither a significant difference in the content of the total ginsenosides between China grown ginseng and Korea grown ginseng, nor remarkably differences in the individual ginsenoside contents of Rb2, Rc, Rd, Re, Rf, and Rg1 in both countries. This may be due to the geographical proximity of Northeast China and South Korea, and they have a similar growing environment for ginseng.
However, NZ-grown ginseng is grown in the Southern Hemisphere, apart from the similar growth conditions including the cold winter, temperate summer, and weakly acidic soil to that ginseng’s natural habitat in Northeast of China and Korea [19
], there are some different growing characteristics in New Zealand, including the volcanic pumice soil and high intensity light radiation. A recent study showed that photosynthetically active radiation, soil, and water potentially had a great impact on ginsenoside accumulation in ginseng roots [20
]. The volcanic pumice soil can provide an excellent environment for root growth because of its unique properties such as dark soil color, unique consistency, low bulk density, difficult clay dispersion, and high water holding capacity [21
]. Additionally, during the Southern Hemisphere summer, NZ receives, on average, 7% more radiation compared to a given latitude in the Northern Hemisphere summer [22
]. It was reported that the total ginsenoside content increased significantly until light transmission rate increased by 20%, but the PPT type ginsenosides increased larger than PPD type ginsenoside, leading to the ratio of PPD/PPT eventually decreasing [23
]. So to some extent, we have reason to believe that NZ’s unique geographical environment encourages elevated ginsenosides (especially PPT type ginsenosides) content compared to ginseng grown in the Northern Hemisphere with similar latitudes. On the other hand, we need to note the limitation of this study, there is only 14 batches of NZ-grown ginseng sample data, a bit smaller compared to hundreds of batches of sample data of Chinese ginseng and Korean ginseng.