Ginseng, also known as Asian ginseng or Korean ginseng, is a plant of Panax ginseng in Araliaceae of UmbelliferaePanax ginseng C. The root of A. mey, as a valuable Chinese herbal medicine, has been used for thousands of years in East Asian countries and is used as a tonic or anti-inflammatory medicine[1], liver protection[2], neuroprotection[3], whitening[4], antitumor[5]Et al. Ginsenosides are important active components of ginseng and belong to triterpenoid glycosides, which can be divided into protopanaxadiol group saponins (PPD type saponins), protopanaxatriol group saponins (PPT type saponins) and oleanane type. Literature research shows that more than 40 human ginsenosides have been isolated from ginseng roots[6]。Chengdu biopurify pharmaceuticals Ltd. can customize various ginsenosides and derivatives related products for customers to meet their R & D and industrialization needs.
Ginsenosides have antioxidant, anti-inflammatory, vasodilatory, anti allergic, anti diabetic and other therapeutic effects[7]Some ginsenosides show their anticancer properties by reducing DNA damage, reducing host susceptibility to mutations, increasing immune monitoring and apoptosis[8]In addition, ginsenosides can effectively improve the efficacy of traditional chemotherapeutic drugs and prevent damage to normal tissues[9-10]。
Ginsenosides have poor water solubility[11], low blood concentration, slow oral absorption, low bioavailability[12], which limits the clinical application of ginsenosides to a certain extent. Studies have shown that the water solubility of ginsenosides can be greatly improved by modifying the molecular structure of ginsenosides[13], stability[14]Targeting[15-16], thereby effectively improving its pharmacological activity[17]In recent years, the research on physical and chemical modification of ginsenosides (especially secondary ginsenosides) has made some progress. This paper reviews the structural modification methods and pharmacological activities of ginsenosides.
1 Acylation modification of ginsenosides
The pharmacokinetic study of ginsenosides showed that 90% of oral ginsenosides were gradually cleaved by colon bacteria in the intestinal tract to obtain 20-O-β-D-Glucopyranosyl-darma-24-ene-3 β, 12 β, 20S-Triol (M1), 20-O-α-L--D-Glucopyranosyl darma-24-ene-3 β, 12 β, 20S-Triol (MC), 20-O-β-D-Glucopyranosyl darma-24-ene-3 β, 6 α, 12 β, 20s tetraol (F1), 3-O-β-D-Glucopyranosyl-20-O-β-D-S-Rare ginsenosides such as triol (PPD), dama-24-en-3 β, 6 α, 12 β, 20s tetranol (PPT) [18].
These metabolites are absorbed in the digestive tract, enter the liver through the blood circulation, and further esterified into ginsenoside fatty acid esters, which can be maintained in the body for a longer time. Modern pharmacological research shows that ginsenoside fatty acid esters have little adverse reactions and high drug activity in vivo, and may be the real anti-tumor active substances in vivo. Therefore, fatty acid esterified ginsenosides are a potential candidate drug.
Wei et al[19]Ginsenoside Rh2 was dissolved in chloroform, octanoyl chloride and triethylamine were slowly added, and the reaction was stirred at room temperature for 15 min to synthesize 12,6 '- dioctanoyl ginsenoside Rh2, namely d-rh2（2）, see Figure 1. MTT assay of human hepatocyte QSG7701 cells in vitro showed that the cytotoxicity of d-rh2 on human hepatocytes was significantly lower than that of ginsenoside Rh2; In vivo antitumor experiments on H22 hepatoma mice showed that the antitumor activity of d-rh2 was equivalent to that of ginsenoside Rh2. Compared with ginsenoside Rh2, d-rh2 can significantly reduce the toxicity to human liver cell line qsg-7701 in vitro, but does not weaken the antitumor activity in vivo. The enhancing effect of d-rh2 on thymus index suggests that d-rh2 may indirectly affect tumor growth by stimulating lymphocytes to produce cytotoxic effects on tumor cells.
Many anticancer drugs (such as oxaliplatin, a third-generation platinum drug), have a good killing effect on cancer cells, but at the same time kill normal cells, resulting in neurotoxicity, blood and gastrointestinal toxicity, nausea and vomiting and other adverse reactions[20]The selective esterification of ginsenoside Rh2 with hydroxyl group can significantly reduce the toxicity of qsg-7701 cells and reduce the damage to normal cells without reducing the anticancer activity, indicating that esterification may be a good method to reduce adverse drug reactions.
Zhang et al[21]Three fatty acid ester derivatives, 3 β - acetoxy Panaxadiol, were synthesized from Panaxadiol with acetic anhydride, palmitoyl chloride and stearoyl chloride as the main reagents（4）, 3 β - palmitic acid acetoxy Panaxadiol（5）And 3 β - stearic acid acetoxy Panaxadiol（6）(Fig. 2).
Zhang's research group [21] used 5-fluorouracil (5-FU) as a positive control to detect the anti-tumor proliferation activity of Panaxadiol fatty acid esters with Vero cell line. MTT assay showed that the derivatives of Panaxadiol4It has strong anti-tumor effect, and the effect is higher than that of the positive control 5-FU, while the compound5and6The anti-tumor effects of the two groups were lower than those of the positive control group. This shows that the length of the fatty chain in fatty acid esters has a significant impact on the anti-tumor effect. The short fatty chain has a good anti-tumor effect, while the long fatty chain has a decreased anti-tumor effect.
Acetylsalicylic acid is one of the most commonly used drugs in the world. In recent years, studies have shown that both acetylsalicylic acid and salicylic acid have antitumor activity[22-23]. Xu et al[24].
The cytotoxicity test of the salicylic acid derivatization and acetylsalicylic acid derivatization of Panax notoginseng saponin acid hydrolysate and the anticancer activity evaluation of the derivatives on human colon cancer HT-29 cells, gastric cancer BGC-823 cells, cervical cancer HeLa cells, human breast cancer MCF-7 cells, human lung cancer A549 cells and two common cancer cell lines showed that all compounds showed low toxicity or non toxicity (IC50> 100 µ mol/l), further indicating that esterification of hydroxyl groups is a good way to reduce adverse drug reactions. In addition, the anticancer activity of ginsenoside acetylsalicylic acid derivatives was significantly stronger than that of ginsenoside salicylic acid derivatives, among which, when the compound3Middle R2For X2， When R3 is h, it has the strongest inhibitory activity on MCF-7 cells, IC50= (2.56 ± 0.09) µ mol/l, which also shows that acetylation can effectively improve the antitumor activity of drugs.
The acylation study of ginsenosides showed that acylation of hydroxyl groups could significantly reduce the toxicity, and the anticancer activity study of different acylated products showed that the anticancer activity of acetylated derivatives of ginsenosides and acetylsalicylic acid derivatives of ginsenosides was significantly better than that of other acylated products, while the anticancer activity was significantly reduced when the carbon chain of acyl groups was increased.
2 Sulfation modification of ginsenosides
Ginsenoside Rh2 is a protopanaxadiol steroidal saponin, with a glucopyranose at position C-3 and a hydroxyl group at positions C-12 and C-20 linked to secondary and tertiary carbons. Fu et al[25]（S）-The hydroxyl groups at position 6 and C-12 of glucopyranose of ginsenoside Rh2 were selectively sulfated, and then two novel sulfated derivatives were obtained by base neutralization1aand1b(Figure 4).1aand1bThe anti-inflammatory effect of LPS on RAW264.7 macrophages in mice showed that after sulfation treatment1aand1bThe water solubility was greatly enhanced, and it significantly inhibited inflammatory cytokines and mediators in a dose-dependent manner, and upregulated anti-inflammatory cytokines, showing stronger anti-inflammatory effects than ginsenoside Rh2.
The sulfation study of ginsenosides showed that the conversion of ginsenosides into bisulfate and then into salt was a good method to improve its water solubility. The improvement of water solubility not only improved the bioavailability, but also enhanced the anti-inflammatory activity of ginsenosides.
3 GinsenosidePEGModification
Ginsenosides are usually degraded by hydrolases in the gastrointestinal tract[26-27]After absorption, so its oral bioavailability is low. With the in-depth study of the pharmacokinetics of ginsenosides, the targeted delivery of ginsenosides has become a research hotspot. Polyethylene glycol (PEG) is a water-soluble, non-ionic, non-toxic polymer material, which is widely used in the field of polymer drug carriers[28]The surface modification of drugs by PEG can improve the water solubility of drugs, protect drugs from proteolysis, prolong the circulation time of drugs in the blood, and reduce the toxicity of drugs[29]At the same time, due to the presence of acid sensitive group ester group, PEG modified drugs can undergo ester degradation in tumor tissues (usually showing weak pH environment) to release drugs, thereby improving the targeting of drugs[30]。
Mathiyalagan et al[31]In order to improve CK（9）PEG modification was carried out on the surface of ginsenosides through ester bonds (Fig. 5). Using MTT assay, the peg-ck was examined with HT-29 cells（10）And PEG cytotoxicity in vitro, peg-ck was found to be less toxic than free CK, indicating the biocompatibility of the hydrophilic polymer. Under weakly acidic conditions (pathophysiological conditions pH 5.0 ～ 6.5), the amount of CK released by peg-ck conjugate is greater than that under normal conditions (physiological conditions pH 7.4). This very high drug solubility, pH selectivity, and enhanced accumulation of peg-ck conjugate at pathophysiological sites may improve the overall efficacy of the drug.
Liu Mei et al[32]Firstly, PEG2000 was used to react with succinic anhydride in the presence of pyridine at 70 ℃ for 24 h to synthesize monomethoxypolyethylene glycol 2000 succinate (mpeg2000-a), and then ginsenoside Rg1 was used（11）Peg-rg1 was synthesized by transesterification of hydroxyl groups on glycosidic bonds with monoesters (Fig. 6). （12）In the stability experiment in rat ex vivo stomach, it was found that ginsenoside Rg1 modified by PEG could improve the problem of easy decomposition in the stomach when it was free, and the stability was greatly improved.
Meanwhile, Liu Mei et al[33]Two groups of SD mice were randomly selected, and ginsenoside Rg1 and peg-rg1 were injected into the tail vein respectively. The targeting coefficients of Ginsenoside Rg1 and peg-rg1 were calculated according to the drug distribution in the organs and plasma of the two groups of mice at different time points. The results showed that peg-rg1 had targeting selectivity to kidney, liver, lung, heart, spleen and liver, and the targeting coefficients of liver, kidney and lung tissues were 9.21, 26.31 and 3.31, respectively, while the targeting coefficient of unmodified ginsenoside Rg1 was greater than 1 only in liver. .
Zhaohaijun et al[34]In the framework of p-nitrophenoxyacylated peg, the phenolic hydroxyl group in the anti-tumor drug etoposide (VP16) structure, the 6-OH on the sugar structural fragment of ginsenoside Rh2 (G-Rh2) and the hydroxyl groups at both ends of the PEG chain were covalently linked under anhydrous conditions by taking advantage of the easy leaving property of the nitrophenoxy group to form a "hydrophobic hydrophilic hydrophobic" amphiphilic copolymer g-rh2-peg-vp16 as shown in Figure 7（13）. It was found that the compound13It has good stability in vitro and in vivo, and can still release enough drugs in the tumor tissue environment of pH 6.5. compound13The copolymer is a promising new anti-tumor drug, which can achieve synergistic anti-tumor effect by combining Chinese and Western drugs.
Repeated -och in PEG structure2CH2-Structural unit, it is reported that[35], at -och2CH2-The oxygen atom in the structural unit has a high electron cloud density around it through the electron withdrawing induced effect, so as to strengthen the hydrogen bonding ability with water molecules and improve the water solubility. Ginsenosides are linked to peg through ester groups. With the help of the strong hydrophilicity of PEG, the solubility and bioavailability in water can be effectively improved. At the same time, the toxicity of ginsenosides modified by PEG is weakened, the stability is increased, and the targeting is improved. Especially, ginsenosides can easily decompose and release drugs in the slightly acidic environment suitable for tumor tissue, which is a good way for cancer targeted therapy.
4 Aminoacidation modification of ginsenosides.The research of ginsenosides in the field of biological engineering and biological engineering and its application in the field of biological engineering and biological engineering and biological engineering and biological engineering and biological engineering and biological engineering and biological engineering and biological engineering and biological engineering
Amino acid refers to the compound with both amino and carboxyl functional groups in the molecule. The carboxyl group of amino acid can be combined with the hydroxyl group in ginsenoside in the form of ester group. Liujihua[36]. The research shows that the larger the structure of amino acid molecule, the more difficult it is to react with saponins; Aminoacidization can occur on one hydroxyl group to produce a single ester, or on multiple hydroxyl groups to produce a poly ester at the same time; Compared with acetyl protection, BOC protected amino acids have relatively less products after reaction, and the later stage separation and purification is simpler. In addition, it was found that amino acids were more likely to react with the hydroxyl group of glucose side chain, and the most likely reaction site was the glc-6 ′ hydroxyl group. The determination of oil-water partition coefficient of amino acid derivatives showed that the water solubility of ginsenosides was significantly improved after amino acid derivatization, and the determination of protein binding rate showed that the anticancer activity of derivatives might be improved.
25-oh-ppd is a promising antitumor natural compound isolated from ginseng fruit. In the study, 25-oh-ppd was found to inhibit the growth of gastric cancer cells, cause cell cycle arrest, and induce cancer apoptosis in vivo, but there was no obvious host toxicity. Therefore, 25-oh-ppd is expected to become an ideal drug for the treatment of cancer[38]To improve the antitumor activity of 25-oh-ppd, Wang et al[37]Amino groups that can increase polarity and BOC protected amino groups that can increase lipophilicity were introduced at C-3 and C-12 of 25-oh-ppd (Fig. 9), and the inhibitory effect on the proliferation of MCF-7 cells, A549 cells and three human colorectal cancer cells was studied. Among the 20 amino acid derivatives of 25-oh-ppd synthesized, the deprotective amino acid derivatives showed higher toxic activity against cancer cells. In addition, there was a strong correlation between the types of amino acid side chains used in derivatization and their biological activities.
5 Oxidative modification of ginsenosides
The double bond of the branched chain in ginsenosides is considered to be one of the reasons for the low solubility in water. To increase by 20（S）-Ginsenoside Rg3, 20（S）-Ginsenoside Rh2 and 20（S）-Water solubility of protopanaxadiol (PD), Jihua Liu[36]For the first time, peroxytrifluoroacetic acid was used to oxidatively modify its side chain to obtain a series of cyclic ethers (FIG. 10). The synthesis of oxidation products of ginsenoside branched double bonds provides a lead compound for finding ginsenoside drugs with higher drug activity. The research on its water solubility and drug activity needs further in-depth study.
Ginsenosides can be oxidized not only on the branch chain, but also on the ring. It has been reported that the oxidation products on the PD ring and the ring opening products of the a ring can inhibit the protease of human immunodeficiency virus HIV and hepatitis C virus HCV[38]Inspired by this, Zhang et al[39].
The cytotoxicity screening of U87 cells showed that the compound1a、3and3dStronger cytotoxic effect than the positive control, in which the compound3IC of50The value was (19.51 ± 1.00) μ mol/l, showing strong anti-tumor cell proliferation activity. The results of MCF-7 cell line showed that,1aand2IC of50The value is 17.73 ～ 23.58 μ mol / L, and its antitumor activity is better than that of IC505-fluorouracil and IC with a value of (29.4 ± 0.7) μ mol/l50The value was (52.62 ± 2.39) μ mol/l of the parent compound PD,3bIC to HeLa cells50The value was 11.65 ～ 19.60 μ mol / L, which showed good antiproliferative activity.
PD and its derivative products were treated by PCC, O2、H2O2The anticancer activity of the products obtained in three different stages of oxidation was compared. It can be seen that in the second stage, O2Product from oxidation24、27and30Of anticancer activity, respectively, than the corresponding stage 3 PCC oxidation products26and29And stage 3 h2O2Oxidation products25、28and31Higher, indicating that the activity of introducing the enol structure into the α - position of the carbonyl group at the 3-position of the a ring is better than that of other oxidation products.
6 Nitrogen hybrid modification of ginsenosides
Among natural products, nitrogen heterocyclic compounds mainly distributed in marine helminths have obvious cytotoxicity[40]In the process of structural modification of oleanolic acid, pyrimidine compounds have general inhibitory activity against breast cancer cells, and its activity is better than that of etoposide, a positive drug[41]。
Zhang et al[39]A fused nitrogen heterocycle derivative of ring a was designed and synthesized, and its antitumor activity was evaluated. First, pyridine chlorochromate (PCC) was used to oxidize PD, and then o-phenylenediamine, ethylenediamine, sulfur, morpholine, hydrazine hydrochloride and other reagents were used to react to obtain nitrogen heterocyclic derivatives (figures 12 and 13). Among the synthesized nitrogen heterocyclic derivatives of Panaxadiol, 20（R）-20,25-epoxy - [5,4-b] - pyrazole-12 β - dammarane（41）Compared with the positive control 5-FU and the parent compound PD, it showed superior antitumor activity and antiproliferative activity, and the activity was significantly higher than that of other derivatives. According to SAR analysis, for A549 cells and 8901 cells, 20（R）-[2,3-b]- pyrazine dammarane-12 β, 20,25-triol（44）It has good anticancer cell proliferation activity, which is 2.6 times that of the positive control 5-FU. In addition, the results of cytotoxicity study showed that all derivatives exhibited low cytotoxic activity against normal cells.
Among the synthesized compounds, pyrazoline compounds41It is presumed that this is related to its special A-ring fused pyrazoline structure; C-17 pyrazine compounds with chain structure fragments44Pyrazine compounds with cyclic structural fragments than C-1721dIt has better anticancer proliferation activity; compound44With43In contrast, the anticancer effect on other cancer cells except HeLa cells is significantly improved, which may be due to the fact that the group connected to its C-12 position is hydroxyl rather than carbonyl[39]。
Imidazole has 2 SP2Five membered aromatic heterocyclic compounds with hybrid nitrogen atoms have unique pharmacological activities, such as anticonvulsant, antibacterial, anticancer, anti-inflammatory, antitumor, antiviral, anti ulcer, analgesic and other pharmacological activities. The introduction of imidazole groups into drugs will also trigger some special biological activities[42]Therefore, it has attracted the attention of researchers.
Steroidal imidazoles have high medical value. Zhangyanlei[43]A series of steroidal imidazole derivatives were designed by connecting Panaxadiol and Panaxatriol with imidazole groups. Panaxadiol failed to synthesize imidazole derivatives, but Panaxatriol successfully synthesized several imidazole derivatives of Panaxatriol oxidation products and imidazole salt derivatives of Panaxatriol oxidation products (FIG. 14).
Zhang yanlei [43] first used Jones reagent to dissolve Panaxatriol（45）The hydroxyl groups at the C-2 and C-6 positions of were oxidized to produce Panaxatriol ketone (compound46）, and then brominated the C-2 position of compound 46 with brominating reagent to obtain the compound47, heated and refluxed with imidazole and imidazole derivatives in toluene to obtain the reaction products of panaxatriol-2-bromo-3,6-dione with imidazole, methylimidazole and benzimidazole, respectively48、49and50. finally, the resulting compounds48Panaxatriol ketone bromide imidazolium salt was synthesized by reaction with benzyl halide51and52; compound24Synthesis of Panaxatriol ketone chloro imidazolium salt with benzyl chloride31The anticancer activity of the compound against HL60 human acute myeloid leukemia cells showed that48、51、52Showed good anticancer activity, among which compounds51Its activity is the strongest, and its effect is better than that of cisplatin.
7 other
The modification methods of ginsenosides include alkylation, tritiation reduction and so on. For example, Jiang Zhuyun[44]The methylation structure modification of the C-12 hydroxyl group in ginsenoside Rg2 molecule was studied by Purdie method, Haworth method, Hakomori method and cicanu method, respectively, in order to change the polarity of ginsenoside Rg2 and improve its function. While wujiuwei et al[45]Protopanaxadiol was dissolved in chloroform, oxidized with potassium dichromate to obtain protopanaxadiol oxide, and then tritiated and reduced with newly prepared sodium boron tritiated to obtain [3,12-3H] protopanaxadiol。 The analysis of the reduced product shows that its indicators can meet the requirements of pharmaceutical and medical research, which is helpful to improve the application of ginsenosides in cancer treatment and diagnosis.
8 Conclusion and Prospect
Ginsenosides are the main bioactive components of ginseng, especially the secondary rare ginsenosides obtained through the degradation of ginsenosides show good anticancer effects[46-47], improve memory[48], neuroprotection[48]And other pharmacological effects, which have received extensive attention. .
The structure modification of ginsenosides by acylation, sulfation, PEG modification, amino acid method, oxidation method, nitrogen hybrid method, alkylation method, tritiation reduction method can effectively improve the water solubility, stability, targeting of ginsenosides, so as to improve the bioavailability and significantly improve the drug activity of ginsenosides.
In the structural modification of ginsenosides, acylation method, sulfation method, PEG modification method, and amino acid method all change the physical and biological activities of ginsenosides by introducing ester groups through esterification and transesterification reactions between specific hydroxyl groups in ginsenosides and derivatization reagents. Different derivatization reagents have different modification effects according to their different structures. ; In acylated derivatives, the introduction of short fatty chain acyl groups (such as acetyl) or acetylsalicylyl groups can effectively improve the anticancer activity of ginsenosides, while the introduction of long fatty chain acyl groups reduces the anticancer activity; Ginsenosides can significantly improve the water solubility and bioavailability of ginsenosides through PEG modification, sulfation and amino acid modification. Among them, PEG method can also increase the stability of ginsenosides and effectively release drugs in the slightly acidic environment suitable for the survival of cancer cells, so as to improve the targeting of drugs. It is a feasible method of Ginsenosides for cancer cell targeted therapy.
The nitrogen hybrid products of ginsenosides are less toxic. The research on the nitrogen hybrid of ginsenosides shows that the introduction of different heterocyclic structures can affect the anticancer activity of ginsenosides, that is, the introduction of some heterocycles significantly improves the anticancer activity, while some heterocycles reduce the anticancer activity. In addition, the influence of heterocycles is also closely related to the structure of ginsenosides, indicating that the anticancer activity of ginsenosides is not a single structural segment in the molecular structure, but the joint synergy of multi-functional groups.
In conclusion, good water solubility and targeting can improve drug efficacy and improve the pharmacokinetics properties of drugs in human body. The physicochemical properties of ginsenosides are related to the number of hydroxyl groups, the structure of mother nucleus, the size and number of linked groups, and the connecting position. Using chemical methods to modify the structure of ginsenoside molecules provides an important direction for improving the bioavailability of ginsenosides. With the rapid development of the pharmaceutical field in recent years, new technologies and new methods emerge in endlessly, and the modification technology of ginsenosides will continue to innovate. More ginsenoside derivatives are expected to be applied in clinic.
Chengdu biopurify pharmaceuticals Ltd. can customize ginsenoside derivatives related products for customers to meet their R & D and industrialization needs.
Conflict of interest All authors declare no conflict of interest
References (omitted)
Source: Zhang Haoran, ye Anqi, Zhang Yuewei, Cheng Leqin. Research progress on derivatization and bioactivity of ginsenosides [j]. Chinese herbal medicine, 2022, 53 (14): 4554-4567