1. Research on the Supramolecules in the Prescription Decoctions
1.1. Baihu Decoction
The Baihu decoction is made from
Anemarrhena asphodeloides,
Glycyrrhizae,
Japonica rice, and
Gypsum. Lv
[1] used high-speed centrifugation and dialysis technology for the phase splitting of the Baihu decoction. Then, they used HPLC to determine the contents of the effective ingredients in the Baihu decoction in different phases. The results showed that the main components of each phase of the Baihu decoction were basically the same, and the content of active ingredients in the nanophase was significantly higher than that in the other phases. Therefore, it is speculated that the supramolecules in the nanophase of the Baihu decoction have a solubilizing effect on the main antipyretic components. In order to study the mechanism of the formation of the supramolecules in the Baihu decoction, particle size, salinity, conductivity, surface tension, TEM, and fingerprint of the supramolecules were measured. Based on the results, it is speculated that the four traditional Chinese medicines in the Baihu decoction all played important roles in the formation of the supramolecules. The macromolecules, such as proteins and polysaccharides, produced by the boiling of
Japonica rice form particles with pores that can serve as the main structure of the supramolecules, allowing the chemical components in the decoction to be embedded.
Anemarrhena asphodeloides contain many antipyretic-related medicinal ingredients, such as neomangiferin and mangiferin, which are poorly water-soluble.
Gypsum contains many inorganic ions. On the one hand, Fe
2+ and Fe
3+ form iron oxides or iron hydroxides with high surface energy that can serve as the central cores of supramolecules. The insoluble components attracting by cores are highly enriched at the periphery of the core, thereby exerting a solubilization effect. On the other hand, Ca
2+, Mg
2+, and Zn
2+ act as zeta-potential regulators that are adsorbed in the supramolecules to regulate the stability of the structure. There are many saponins in
Glycyrrhizae, such as glycyrrhizic acid and glycyrrhetinic acid, which are important surface-active substances that can improve the solubility of mangiferin and neomangiferin and regulate the stability of the supramolecules
[2][3]. An efficacy test showed that the antipyretic effect on rabbits and the effect of reducing the level of inflammatory factors in the serum were better for supramolecules than for the components in true-solution phase because of supramolecules was easily ingested by cells and targeted the brain and lungs, indicating that the supramolecules are key to the antipyretic mechanism of the Baihu decoction
[4].
1.2. Huanglian Jiedu Decoction
The Huanglian Jiedu decoction is composed of four commonly used medicinal herbs, namely,
Coptidis Rhizoma,
Radix Scutellariae,
Phellodendri Cortex, and
Gardeniae Fructus. There was obvious precipitation in the decoction, and the precipitation rate reached 7.13%
[5]. Fang
[6] used the HPLC method to determine the precipitation components of the Huanglian Jiedu decoction and found that 81% of the precipitation was organic acids and alkaloids, of which baicalin accounted for 42.12% and berberine accounted for 31.17%. This study revealed that the compound precipitation from the Huanglian Jiedu decoction was mainly composed of an acid–alkali complex. Baicalin is acidic due to the presence of carboxyl groups in its structure, and it is prone to precipitation reactions with alkaloids such as berberine. Therefore, from the perspective of molecular thermodynamics, all the sources of precipitation, parameters of interaction, and binding abilities of different medical combinations during the formation of the precipitate in the Huanglian Jiedu decoction were explored. The original decomposed-recipe experiment indicated that the combinations that could produce obvious precipitates when they were mixed were
Scutellariae Radix–
Coptidis Rhizoma and
Scutellariae Radix–
Phellodendri Chinensis Cortex. The amount of precipitation for the
Scutellariae Radix–
Coptidis Rhizoma was the highest. Then, isothermal titration calorimetry (ITC) was used to determine the binding heat and thermodynamic parameters of the binding reactions, and the results show that the precipitation-formation process is a chemical reaction that drives the non-covalent bonding of enthalpy, rather than a simple physical aggregation and adsorption precipitation. Therefore, it is believed that the precipitate in the Huanglian Jiedu decoction is formed by self-assembly
[7]. The compositions of both the supernatant and naturally supramolecules of the Huanglian Jiedu decoction were further analyzed by UHPLC–Q–Orbitrap HRMS. The results showed that the compositions of the supernatant and the supramolecules were the same. Due to the self-assembly complexation, the supramolecule’s content of baicalin and berberine was significantly higher than that of the supernatant
[8]. Based on these studies, Zhang
[9] used baicalin and berberine to synthesize and form the precipitate in the Huanglian Jiedu decoction and found that baicalin and berberine formed complex molecules at a molar ratio of 1:1 through electrostatic attraction. From the basic unit, further assembly forms the supramolecules in the Huanglian Jiedu decoction. Cobalt chloride was used to induce PC12 cells to establish a nerve-injury model. The supramolecular precipitate in the Huanglian Jiedu decoction and the simulated synthetic baicalin–berberine supramolecules showed good protective effects.
1.3. Gegen Qinlian Decoction
The Gegen Qinlian decoction is composed of four traditional Chinese medicines:
Pueraria lobata,
Scutellaria baicalensis,
Coptis chinensis, and
Glycyrrhizae. The changes in the content of active ingredients before and after the formulation of the Gegen Qinlian decoction was determined by HPLC. The results showed that, when
Pueraria lobata was decoctioned with
Coptis chinensis and
Scutellaria baicalensis, respectively, it could solubilize berberine, palmatine, baicalein, and wogonin. Among them, the reason
Puerariae promotes the dissolution of baicalein and wogonin may be the formation of molecular complexes
[10]. Hu
[11] found that puerarin, daidzein, and daidzein are the main components of supramolecules in the Gegen Qinlian decoction and have good activity in vitro. Guo
[12] used ultrafiltration centrifuge tubes to filter the Gegen Qinlian decoction. After intercepting most of the supramolecule particles, the ingredients in the decoction were tested. The results showed that the contents of several main active ingredients in the decoction were reduced to varying degrees after ultrafiltration. This shows that the supramolecules in the decoction are an important substance that exerts medicinal effect. Experiments by Lin also proved this point. The supramolecules showed stronger activities than the supernatant on many tests. In vivo experiments showed that the supramolecules of the Gegen Qinlian decoction showed a stronger hypoglycemic effect. In vitro experiments showed that the supramolecules in the decoction had stronger antioxidant effects, better protective effects on cells, and were basically non-toxic. High absorption rates of baicalin indicated that the supramolecules changes pharmacokinetics of Gegen Qinlian decoction and improves the bioavailability of insoluble phytochemicals, like baicalin, may be essential for the synergistic actions in the herbal decoction. It showed that the supramolecules in the Gegen Qinlian decoction had a better medicinal effect
[13]. When investigating the protein self-assembly behavior during the Gegen Qinlian decoction, Lin separated Pueraria protein and Coptis protein and found that the two proteins could form supramolecules under simulated decoction conditions. The experimental results showed that the efficiency of Pueraria protein encapsulated puerarin was 33.88%, and the efficiency of Coptis protein encapsulated berberine hydrochloride was 44.2%
[14].
1.4. Maxing Shigan Decoction
The Maxing Shigan decoction is a classic prescription consisting of
Ephedra,
Radix Glycyrrhizae,
Semen Armeniacae Amarum, and
Gypsum. Studies have found that the chemical components of the Maxing Shigan decoction intertwine to form a new physical phase during the decoction process, which leads to the heterogeneous distribution of the ingredients of the decoction. Pharmacodynamic experiments showed that the supramolecular structure of the Maxing Shigan decoction has good antibacterial activity, and the composition test showed that the supramolecules contain organic active small molecules such as ephedrine; amygdalin and glycyrrhizic acid; Ca, K, and Mg; and other inorganic ingredients
[15]. Research by Zhou showed that ephedrine (99.7%) and pseudoephedrine (95.5%) in the Maxing Shigan decoction are mainly present in supramolecules. It is speculated that amphiphilic molecules, such as ephedrine and pseudoephedrine, are adsorbed on the supramolecules through hydrogen bonding, electrostatic interactions, and van der Waals attraction
[16]. Du
[17] compared the in vitro change in antiviral activity in the Maxing Shigan decoction, determined by the MTT method, before and after filtration with a 0.45 μm cellulose acetate film. The results showed that the antiviral activity of the decoction was significantly reduced after filtration. The reason is that a large number of supramolecules are removed by filtration, which proves that the anti-influenza-virus activity of the Maxing Shigan decoction is related to its supramolecules.
1.5. Siwu Decoction
The Siwu decoction is composed of
Rehmannia glutinosa,
Angelica sinensis,
Paeonia lactiflora, and
Ligusticum chuanxiong. Zhang used differential centrifugation to obtain supramolecules with a particle size distribution of 100–1000 nm in the Siwu Decoction. Assays showed that the supramolecules contained a large amount of protein and polysaccharides and a small amount of DNA. Pharmacological studies showed that heme synthesis, degradation, and protein binding were closely related with the supramolecules, and it had regeneration-promoting effects on the damage of hematopoietic function. Therefore, it is speculated that supramolecules greatly contribute to the medicinal effect of the Siwu Decoction
[18].
1.6. Shaoyao Gancao Decoction
The Shaoyao Gancao decoction is composed of two traditional Chinese medicines:
Paeoniae Radix and
Glycyrrhizae Radix. The main active components of the monarch medicine
Paeoniae Radix are monoterpene glycosides. These glycosides are more polar and difficult to absorb in the gastrointestinal tract. However, when it is combined with
Glycyrrhizae Radix, the absorption efficiency for the active ingredients of
Paeoniae Radix is effectively improved
[19]. Particle-size analysis and morphological observation showed that there were supramolecules with a particle size of approximately 200 nm in the Shaoyao Gancao decoction, and the supramolecules were irregularly spherical under TEM observation. The experimental results showed that the supramolecules in the Shaoyao Gancao decoction could effectively encapsulate the active ingredients in
Paeoniae Radix. After entering the body, it not only exerts a sustained release effect but also improves the absorption efficiency for the drug in the ileum
[20]. Shen prepared paeoniflorin-loaded glycyrrhizic acid supramolecules using the ultrasonic dispersion method to improve the oral absorption of paeoniflorin. The in vivo pharmacokinetics showed that the C
max and AUC0–t values of paeoniflorin encapsulated by supramolecules formed by glycyrrhizic acid were approximately 2.18 and 3.64 times higher than those of paeoniflorin in solution
[21].
2. Research into the Supramolecules of Medicinal–Pair Decoction
2.1. Aconiti Laterdis and Glycyrrhizae Radix Co-Decoction
Aconiti Laterdis and
Glycyrrhizae Radix, a classic medicinal combination, can reduce the toxicity and increase the effects after compatibility, but the mechanism is not yet clear. In analyzing the differences in the physicochemical properties of the
Aconiti Laterdis and
Glycyrrhizae Radix decoction before and after combination, Chen found that the particle size of the combined decoction was larger than that of the single decoction. Therefore, it is speculated that the supramolecules produced by the combined decoction may be the material basis for synergism and detoxification after compatibility
[22]. Then, they used HPLC–MS to identify 36 components from the supramolecules in the combined decoction, among which there were 11 compounds from
Glycyrrhizae Radix and 25 compounds from
Aconiti Laterdis. According to these confirmed compounds, the alkaloid compounds in the combined decoction were significantly different from those of the single decoction. This shows that there were some changes in the alkaloid compounds in the decoction after the combination of
Glycyrrhizae Radix
[23]. The contents of six ester alkaloids in the supramolecules formed before and after compatibility were compared simultaneously using the HPLC–TOF–MS method, and the supramolecular changes were identified using FTIR and second-derivative spectra. The results showed that, in the process of co-decocting, a large number of ester alkaloids in
Aconiti Laterdis combined with the components in
Glycyrrhizae Radix to form a supramolecule. It is speculated that the mechanism may be the association between the tertiary amine N in the alkaloid and the carboxyl in the glycyrrhizic acid
[24]. Zhang
[25] investigated the intestinal absorption and pharmacokinetic characteristics of the three diester-types diterpene alkaloids in the supramolecules of the co-decoction. The results showed that the diester-type diterpene in the supramolecules prevents dose dumping and prolongs the average residence time, thereby effectively reducing the toxicity of aconite after oral administration.
Apart from acid–base neutralization, studies have shown that glycyrrhizae protein is also an entry point to clarifying the mechanism of reducing toxicity. Rao
[26][27] found that glycyrrhizae protein could be separated by anion-exchange chromatography. When the pH was 5, the glycyrrhizae protein could form supramolecules with a stable particle size with aconitine, and the embedding rate was 28.22%. Acute toxicity experiments in mice showed that glycyrrhizae protein attenuated the toxicity after embedding aconitine.
2.2. Glycyrrhizae Radix–Coptis Chinensis Co-Decoction
Glycyrrhizae Radix–
Coptis Chinensis has a wide range of clinical applications, but the drug pair produces a large amount of self-precipitation when co-decocted. When studying the supramolecules of the co-decocting of
Glycyrrhizae Radix–
Coptis Chinensis, it was found that the components in the supramolecules of the combined decoction were significantly different from those of the single decoctions, and the combined decoction contained more active ingredients
[28]. Zhao
[29] used HPLC to detect the components in the supramolecular precipitate; the results showed that it was mainly small molecules such as glycyrrhizic acid and berberine. The investigation of the solubility of supramolecular precipitates in digestive conditions showed that the supramolecules formed by the compatibility of
Glycyrrhizae Radix and
Coptis Chinensis allowed for the slow release of berberine. The formed supramolecules not only ensure the therapeutic effect of berberine but also prevent the side effects of
Coptis Chinensis inhibiting yang, damaging the spleen and stomach, confirming the rationality of the compatibility law for
Glycyrrhizae Radix and
Coptis Chinensis. Li
[30] found that
Glycyrrhizae Radix crude protein and berberine could form spherical supramolecular particles under the induction of weak bonds, such as electrostatic attractions and hydrophobic interactions, after co-decoction. The antibacterial activity of the supramolecules is significantly better than that of berberine and mechanical mixtures. The amino acid residues on the surface of glycyrrhizae protein could make itself adsorbed on Staphylococcus aureus. Therefore, glycyrrhizae protein–berberine supramolecules may adhere to the bacterial surface after interacting with bacteria, and the supramolecules continuously release berberine, which increases the concentration of berberine around the bacteria and increases the uptake, resulting in a stronger antibacterial effect. These experiments indicating that the interaction between glycyrrhizae protein and berberine during the heating process promotes a better effect of the medicinal ingredients.
3. Research into the Supramolecules of a Single-Drug Decoction
3.1. Banlangen Decoction
Isatis indigotica Fort is one of the few Chinese medicines with good antiviral effects. Lin
[31] tracked and compared the changes in the components of
Isatis indigotica before and after decoction and found that spherical polymers formed during the boiling process. The supramolecules were formed by the inherent natural components in the decoction, such as proteins, sugars, amino acids, and fatty acids, through self-assembly. The characterization results from TEM and laser particle size analysis showed that the supramolecules were composed of a series of particles of different sizes. Further research has shown that the pH of the buffer during the boiling of
Isatis indigotica determines the pH response of the supramolecules, and this pH response is microscopically manifested as the aggregation and dispersion of the supramolecules. Among them, the Banlangen decoction shows the lowest light-scattering intensity when the pH is close to neutral, and the light-scattering intensity increases under acid and alkali conditions, indicating that the particles of supramolecules become larger. Experiments show that the supramolecules of different forms have different antiviral effects. He
[32] used gel chromatography to separate and purify the supramolecules in the Banlangen decoction and found that this supramolecule shows not only pH responsiveness but also temperature responsiveness. Zhou
[33] identified two constitutive glycosylated proteins from supramolecules in the Banlangen decoction. The N-terminal amino acid sequences are V–X–R–E–V–V–K–D–I and V–V–R–E–V–V–K–D–I–A–G–A–V–Q–T–N–E–Q–Y. In order to clarify the structure, cDNA cloning and glycosylation–site analysis were carried out. The primary-structure comparison showed that the two glycosylated proteins have high homology, representing allelic variants of the same gene. Based on this, they obtained the highly homologous amino acid sequence of the non-glycosylated protein. Furthermore, they used pepsin hydrolysis and MS to identify four possible glycosylation adducts in the supramolecules. From these studies, it could be observed that the supramolecules isolated from the Banlangen decoction were a smart nanocomponent composed of a boiling-stable protein, which was pH responsive and temperature responsive, and could be used as a prototype in the future to develop a smart, safe, and stable drug-delivery vehicle.
3.2. Taizishen Decoction
Cai
[34] separated the supramolecules in the Taizishen decoction by gel-filtration chromatography and analyzed their immune activity. They found that the isolated supramolecules could stimulate the proliferation of mouse spleen cells and promote the secretion of the immune factors IL–10, IL–13, TNF–α, and IFN–γ. This proved that the supermolecule is the main medicinal ingredient of the Taizishen decoction. Weng
[35] obtained the crude protein from the Taizishen decoction using ammonium sulfate sedimentation technology. After heating at 100 °C for 30 min and adjusting the pH to 5.70, supramolecules with a particle size of approximately 70 nm were obtained, which could effectively improve the solubility of curcumin.
This entry is adapted from the peer-reviewed paper 10.3390/molecules27103268