Intestinal absorption of aloin, aloe-emodin, and aloesin; A comparative study using two in vitro absorption models

Aloesin ameliorates hypoxic-ischemic brain damage in neonatal mice by suppressing TLR4-mediated neuroinflammation

BACKGROUND

At present, neonatal hypoxic-ischemic encephalopathy (HIE), especially moderate to severe HIE, is a challenging disease for neonatologists to treat, and new alternative/complementary treatments are urgently needed. The neuroinflammatory cascade triggered by hypoxia-ischemia (HI) insult is one of the core pathological mechanisms of HIE. Early inhibition of neuroinflammation provides long-term neuroprotection. Plant-derived monomers have impressive anti-inflammatory effects. Aloesin (ALO) has been shown to have significant anti-inflammatory and antioxidant effects in diseases such as ulcerative colitis, but its role in HIE is unclear. To this end, we conducted a series of experiments to explore the potential mechanism of ALO in preventing and treating brain damage caused by HI insult.

MATERIALS AND METHODS

Hypoxic-ischemic brain damage (HIBD) was induced in 7-day-old Institute of Cancer Research (ICR) mice, which were then treated with 20 mg/kg ALO. The neuroprotective effects of ALO on HIBD and the underlying mechanism were evaluated through neurobehavioral testing, infarct size measurement, apoptosis detection, protein and messenger RNA level determination, immunofluorescence, and molecular docking.

RESULTS

ALO alleviated the long-term neurobehavioral deficits caused by HI insult; reduced the extent of cerebral infarction; inhibited cell apoptosis; decreased the levels of the inflammatory factors interleukin (IL)-1β, IL-6, and tumor necrosis factor-α; activated microglia and astrocytes; and downregulated the protein expression of members in the TLR4 signaling pathway. In addition, molecular docking showed that ALO can bind stably to TLR4.

CONCLUSION

ALO ameliorated HIBD in neonatal mice by inhibiting the neuroinflammatory response mediated by TLR4 signaling.

In vivo metabolism combined network pharmacology to identify anti-constipation constituents in Aloe barbadensis Mill

ETHNOPHARMACOLOGICAL RELEVANCE

Aloe barbadensis Mill. (Aloe vera), is a homology of medicine and food plant, widely applied in functional food, cosmetics, and medicine. Aloe vera whole leaf extract, one of the most popular traditional Chinese medicines (TCMs), is mainly used in China to treat functional constipation.

AIM OF THE STUDY

To elucidate the active constituents of Aloe vera for treating functional constipation.

MATERIALS AND METHODS

Prototype constituents and metabolites in rat plasma and excreta after oral administration of Aloe vera whole leaf extract were identified by UPLC-Q-TOF/MS, and the pharmacokinetics (PK) properties of its key anti-constipation constituents speculated by network pharmacology were investigated via the established UFLC-MS/MS method.

RESULTS

A total of 13 prototype constituents and 56 metabolites were identified in rat plasma, urine, and feces after oral administration of Aloe vera. Among them, aloesin, aloenin, aloin B, aloin A, and aloe-emodin were intimately connected to the core targets of constipation in network pharmacology analysis, and recognized as major anti-constipation constituents in Aloe vera. The validated quantitative method of the six active constituents in rat plasma exhibited good linearity, and lower limits of quantification (0.64-1.95 ng/mL). Aloin A, aloin B, aloeresin D and aloe-emodin exhibited better absorption and slower elimination rate, whereas the others, including aloesin and aloenin showed fast absorption and elimination in rat plasma after oral administration of Aloe vera. Aloin A and its isomer aloin B present similar Tmax and t1/2 but different AUC and Cmax values, indicating different relative bioavailability. The results suggested that aloin A, aloin B and aloe-emodin may be key constituents of Aloe vera for the treatment of constipation, and the other constituents including aloeresin D also contribute to its anti-constipation.

CONCLUSIONS

This study will benefit understanding the contributions of those constituents for the anti-constipation effect of Aloe vera and also provide valuable information for its application in functional food development and clinics.

Impact of dry-off and lyophilized Aloe arborescens supplementation on plasma metabolome of dairy cows

Positive effects have been observed as a result of Aloe arborescens supplementation in the dry-off phase in dairy cows. Metabolomic approaches can provide additional information about animal physiology. Thus, we characterized plasma metabolome around dry-off in 12 cows supplemented (AL) or not (CTR) with 10 g/d of lyophilized A. arborescens with an untargeted metabolomic approach. Overall, 1658 mass features were annotated. Regardless of treatment, multivariate statistics discriminated samples taken before and after dry-off. Overall, 490 metabolites were different between late lactation and early dry period, of which 237 were shared between AL and CTR. The most discriminant compounds (pentosidine and luteolin 7-O-glucoside) were related to the more fibrous diet. Pathway analysis indicated that pyrimidine and glycerophospholipid metabolisms were down-accumulated, suggesting reduced rumen microbial activity and liver load. Samples from AL were discriminated from CTR either the day of dry-off or 7 days after. At dry-off, aloin and emodin were the most discriminant metabolites, indicating that Aloe's bioactive compounds were absorbed. Seven days later, 534 compounds were different between groups, and emodin was among the most impacted. Pathway analysis highlighted that glycerophospholipid, pyrimidine, and folate metabolisms were affected. These results might indicate that Aloe has positive effects on liver function and a modulatory effect on rumen fermentation.

Shouhui Tongbian Capsule ameliorates constipation via gut microbiota-5-HT-intestinal motility axis

Constipation has become an epidemic enteric medical problem, accompanied with increasing long-term sequelae. Gut microbiota and serotonin (5-HT) have been believed as predominant player in the treatment of constipation. In clinical practices, Shouhui Tongbian Capsule (SHTB) was found to effectively improve constipation symptoms and promote gastrointestinal motility. However, the specific mechanism of SHTB is not clearly elucidated. Our current study aims to explore the therapeutic effects of SHTB against the development of constipation and the underlying mechanisms related to gut bacterial and 5-HT. We established loperamide hydrochloride (LH)-induced experimental constipation mouse model to evaluate the effect of SHTB. 16S RNA sequencing, fecal microbiota transplants (FMT), high performance liquid chromatograph, and molecular biological analysis were performed to investigate the potential mechanisms of SHTB. Our data demonstrated that SHTB significantly ameliorated LH-induced experimental constipation and accelerated enteric motility via promoting 5-HT biosynthesis in enterochromaffin cells and enteric neuron growth of the enteric nervous system (ENS) in both the small intestine and colon. Additionally, SHTB significantly modulated gut microbiota dysbiosis and potentially altered microbiota metabolites to enhance intestinal 5-HT production. Finally, FMT study confirmed that the effects of SHTB on 5-HT production and constipation are dependent on modulating intestinal microbiota dysbiosis. In conclusion, our current study deciphered therapeutic mechanism of SHTB in the treatment of experimental constipation from perspectives of gut microbiota-5-HT-intetinal motility axis and provides novel insights into the appropriate and safe application of SHTB in the clinic.

Shabyar Ameliorates High Glucose Induced Retinal Pigment Epithelium Injury Through Suppressing Aldose Reductase and AMPK/mTOR/ULK1 Autophagy Pathway

Shabyar (SBA) is a traditional medicine formula for relieving vision loss caused by factors including diabetic retinopathy (DR) in clinics. However, the mechanism of it on retina protective effect still unclear. The present study aimed to investigate whether its protective effect was related to aldose reductase (AR) inhibition and retinal pigment epithelial cell injury mediated by autophagy or not. Human retinal pigment epithelial cells (ARPE-19) induced by high glucose was used as a model in vitro, with Epalrestat (EPL, AR inhibitor) and Difrarel (DFR, DR therapeutic drug) as positive controls. Western blotting and Polyol pathway products assay showed that SBA reduced the expression of AR protein and the content of ROS, and sorbitol, increased the level of Na⁺-K⁺-ATPase and alleviated cell edema. Western blotting and DCFH-DA probe assay showed that SBA decreased pAMPK/AMPK and pULK1/ULK1 which associated with autophagy initiation, down-regulated Beclin-1, Atg3, Atg5, Atg7, LC3 II and Bax/Bcl2 ratio, and up-regulated pmTOR/mTOR, SQSTM1/p62 and mitochondrial membrane potential (MMP), reduces intracellular autophagosomes. Real-Time PCR assay showed that SBA had no significant effect on mRNA expression of AR and mTOR. These data demonstrated that SBA treatment inhibits the autophagy of ARPE-19 through the AMPK/mTOR/ULK1 signaling pathway, and reduced early-stage apoptosis occurred by high glucose. These findings reveal the protective role and mechanism of SBA on retinal pigment epithelium, and provide experimental basis for the clinical application of SBA in the treatment of DR.

Pharmacokinetics, Tissue Distribution, and Excretion Characteristics of a Radix Polygoni Multiflori Extract in Rats

Although progress has been achieved in the pharmacological activity and toxicity of Radix Polygoni Multiflori (RPM), the chemical basis of its toxicity is still unclear. Here, we performed a multicompound pharmacokinetic analysis and investigated the tissue distribution and excretion characteristics of RPM components after oral administration in rats. The findings demonstrated that the active ingredients of the RPM extract were quickly absorbed after oral administration, with high exposure levels of emodin, 2,3,5,4′-teterahydroxystilbene-2-O-β-D-glucoside (TSG), citreorosein, torachrysone-8-O-glucoside (TG), emodin-8-O-β-D-glucoside (EG), and physcion-8-O-β-D-glucoside (PG). The tissue distributions of emodin, TSG, TG, EG, and PG were high in the liver and kidney. These components were the key contributors to the effectiveness and toxicity of RPM on the liver and kidney. Most of the active ingredients were mainly excreted through feces and bile, while a few were converted into other products in the body and excreted through urine and feces.

The potential health benefits of aloin from genus Aloe

The Aloe species is known for its medicinal and cosmetic properties. Aloin is an active ingredient found in the leaves of medicinal plants of the genus Aloe. Aloin has attracted considerable interest for its antiinflammatory, anticancer, antibacterial, and antioxidant activities. However, since its clinical application is restricted by its unclear mechanism of action, a deeper understanding of its pharmacological activity is required. This review provides an overview of current pharmacological and toxicological studies published in English from February 2000 to August 2021. Herein, we summarized the sources and potential health benefits of aloin from a clinical application perspective to guide for further studies on the sources of aloin, aimed at efficiently increasing aloin production. Importantly, the function and mechanism of action of aloin remain unclarified. In future research, it is necessary to develop new approaches for studying the pharmacological molecular mechanisms underlying the activity of this compound against various diseases.

Inhibition of cell-intrinsic NF-κB activity and metastatic abilities of breast cancer by aloe-emodin and emodic-acid isolated from Asphodelus microcarpus

Anthraquinones are a major class of compounds naturally occurring in Asphodelus microcarpus. The pharmacological actions of anthraquinones in cancer cells are known to induce apoptosis or autophagy, and revert multidrug resistance. In this study, five anthraquinone-type analogs were isolated from the methanol extract of A. microcarpus leaves and identified as, emodin, rhein, physcion, aloe-emodin, and emodic acid. Among them, aloe-emodin and emodic-acid strongly inhibited the proliferation, cells-intrinsic NF-κB activity and metastatic ability of breast cancer. Although aloe-emodin inhibited p38 and ERK phosphorylation, emodic-acid more markedly inhibited JNK, in addition to p38 and ERK phosphorylation. Both aloe-emodin and emodic-acid inhibited the secretion of the pro-tumorigenic cytokines IL-1β and IL-6, and VEGF and MMP expression, and subsequently inhibited the invasive and migratory potential of 4T1 cells. Thus, our study demonstrated the effects of aloe-emodin and emodin-acid in controlling the migratory and invasive ability of 4T1 breast cancer cells, in addition to inhibiting NF-κB activity and the expression of its downstream target molecules.

Aloin promotes cell apoptosis by targeting HMGB1-TLR4-ERK axis in human melanoma cells

Aloin (ALO) is the major anthraquinone glycoside purified from the Aloe species. It is well known for its anti-tumor effects. However, the protective effects of ALO in melanoma cancer and underlying molecular mechanism remain unclear. High-mobility group protein B1 (HMGB1) is an intracellular protein, which has closely association with cell survival, proliferation and metastasis in various cancers. In this study, we explored the effect of ALO on cell survival and apoptosis by targeting HMGB1 signal pathway. We confirmed that ALO exerts a strong effect on promoting cell apoptosis of melanoma cells in vitro. Furthermore, HMGB1 release was significantly inhibited in melanoma cancer cells treated with ALO. Knockdown of HMGB1 could enhance melanoma cell death that is induced by ALO treatment. Moreover, HMGB1 facilitated ALO mediated melanoma cell apoptosis by binding to its receptor, Toll-like receptor 4 and activating extracellular regulated protein kinases (ERK) signal pathway. Altogether, our study demonstrated that ALO plays an important role in promoting apoptosis of melanoma cells by inhibiting HMGB1 release and activation of downstream ERK signal pathway.

Aloe-emodin: A review of its pharmacology, toxicity, and pharmacokinetics

Aloe-emodin is a naturally anthraquinone derivative and an active ingredient of Chinese herbs, such as Cassia occidentalis, Rheum palmatum L., Aloe vera, and Polygonum multiflorum Thunb. Emerging evidence suggests that aloe-emodin exhibits many pharmacological effects, including anticancer, antivirus, anti-inflammatory, antibacterial, antiparasitic, neuroprotective, and hepatoprotective activities. These pharmacological properties lay the foundation for the treatment of various diseases, including influenza virus, inflammation, sepsis, Alzheimer's disease, glaucoma, malaria, liver fibrosis, psoriasis, Type 2 diabetes, growth disorders, and several types of cancers. However, an increasing number of published studies have reported adverse effects of aloe-emodin. The primary toxicity among these reports is hepatotoxicity and nephrotoxicity, which are of wide concern worldwide. Pharmacokinetic studies have demonstrated that aloe-emodin has a poor intestinal absorption, short elimination half-life, and low bioavailability. This review aims to provide a comprehensive summary of the pharmacology, toxicity, and pharmacokinetics of aloe-emodin reported to date with an emphasis on its biological properties and mechanisms of action.

Antiglycation Activity and HT-29 Cellular Uptake of Aloe-Emodin, Aloin, and Aloe arborescens Leaf Extracts

Aloe arborescens is a relevant species largely used in traditional medicine of several countries. In particular, the decoction of leaves is prepared for various medicinal purposes including antidiabetic care. The aim of this research was the study of the antiglycation activity of two A. arborescens leaf extracts and isolated compounds: aloin and aloe-emodin. These phytoconstituents were quantitatively assessed in methanolic and hydroalcoholic extracts using high performance liquid chromatography (HPLC) analysis. In addition, the total phenolic and flavonoid contents were detected. In order to study their potential use in diabetic conditions, the antiglycation and antiradical properties of the two extracts and aloin and aloe-emodin were investigated by means of bovine serum albumin (BSA) and 1,1-diphenyl-2-picryl-hydrazil (DPPH) assays; further, their cytotoxicity in HT-29 human colon adenocarcinoma cells was evaluated by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay. Furthermore, the ability of aloin and aloe-emodin to permeate the cellular membranes of HT-29 cells was determined in order to estimate their potential in vivo absorption. This assessment indicated that aloe-emodin can substantially pass through cell membranes (~20%), whereas aloin did not permeate into HT-29 cells. Overall, the data show that both the methanolic and the hydroalcoholic A. arborescens extracts determine significant inhibition of glycation and free-radical persistence, without any cytotoxic activity. The data also show that the antiglycation and the antiradical activities of aloin and aloe-emodin are lower than those of the two extracts. In relation to the permeability study, only aloe-emodin is able to cross HT-29 cellular membranes, showing the attitude to pass through the intestinal layer. Overall, the present data surely support the traditional use of A. arborescens leaf extracts against hyperglycemic conditions, while aloin and aloe-emodin as potential drugs need further study.

Dose-Dependent Effects of Aloin on the Intestinal Bacterial Community Structure, Short Chain Fatty Acids Metabolism and Intestinal Epithelial Cell Permeability

Aloe leaf or purified aloin products possess numerous therapeutic and pharmaceutical properties. It is widely used as ingredients in a variety of food, cosmetic and pharmaceutical products. Animal studies have shown that consumption of aloe or purified aloin cause intestinal goblet cell hyperplasia, and malignancy. Here, we tested antibacterial effects of aloin, against intestinal commensal microbiota. Minimum inhibitory concentration of aloin for several human commensal bacterial species (Gram-positive and Gram-negative) ranged from 1 to 4 mg/ml. Metabolism studies indicated that Enterococcus faecium was capable of degrading aloin into aloe-emodin at a slower-rate compared to Eubacterium spp. As a proof of concept, we incubated 3% rat fecal-slurry (an in vitro model to simulate human colon content) with 0.5, 1, and 2 mg/ml of aloin to test antimicrobial properties. Low aloin concentrations showed minor perturbations to intestinal bacteria, whereas high concentration increased Lactobacillus sp. counts. Aloin also decreased butyrate-production in fecal microbiota in a dose-dependent manner after 24 h exposure. The 16S rRNA sequence-data revealed that aloin decreases the abundance of butyrate-producing bacterial species. Transepithelial resistant result revealed that aloin alters the intestinal barrier-function at higher concentrations (500 μM). In conclusion, aloin exhibits antibacterial property for certain commensal bacteria and decreases butyrate-production in a dose -dependent manner.

HIGHLIGHTS

    –Aloin exhibits antibacterial properties for certain intestinal commensal bacteria.

    –In rat fecal slurry (an in vitro model to simulate human colon content), longer aloin exposure (24 h) decreases the butyrate production in dose dependent manner.

    –The 16s rRNA sequencing data show that aloin decreased the abundance of butyrate producing bacterial species.

    –Rat intestinal commensal bacteria metabolized aloin into aloe-emodin.

    –Aloin altered the intestinal epithelial cells barrier integrity, however, the metabolic product of aloin - Aloe-emodin did not alter epithelial cells permeability.

Self-assembled 4-(1,2-diphenylbut-1-en-1-yl)aniline based nanoparticles: podophyllotoxin and aloin as building blocks

The ability of 4-(1,2-diphenylbut-1-en-1-yl)aniline as a self-assembly inducer is reported. The conjugation of this moiety with aloin or podophyllotoxin resulted in spherical nanoparticles that were characterized by Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM) and NanoSight technology. A preliminary biological evaluation on two cancer cell lines is reported.

Layer-by-layer assembled milk protein coated magnetic nanoparticle enabled oral drug delivery with high stability in stomach and enzyme-responsive release in small intestine

We report a novel drug delivery system composed of layer-by-layer (LBL) milk protein casein (CN) coated iron oxide nanoparticles. Doxorubicin (DOX) and indocyanine green (ICG) were selected as model drug molecules, which were incorporated into the inner polymeric layer, and subsequently coated with casein. The resulting casein coated iron oxide nanoparticles (CN-DOX/ICG-IO) were stable in the acidic gastric condition with the presence of gastric protease. On the other hand, the loaded drugs were released when the casein outer layer was gradually degraded by the intestinal protease in the simulated intestine condition. Such unique properties enable maintenance of the bioactivity of the drugs and thus enhance the drug delivery efficiency. Ex vivo experiments showed that the LBL CN-DOX-IO improved the translocation of DOX across microvilli and its absorption in the small intestine sacs. In vivo imaging of mice that were orally administered with these LBL CN-ICG-IO nanostructures further confirmed that the reported drug delivery vehicles could pass the stomach without significant degradation, and then accumulated in the small intestine. In addition, the magnetic iron oxide nanoparticle core offered an MRI contrast enhancing capability for in vivo imaging guided drug delivery. Therefore, the reported LBL CN-DOX/ICG-IO is a promising oral drug delivery nanoplatform, especially for drugs that are poorly soluble in water or degradable in the gastric environment.

Potential antineoplastic effects of Aloe-emodin: a comprehensive review

Aloe-emodin (AE), a bioactive anthraquinone derived from both Aloe vera and Rheum officinale, has recently been demonstrated to have various pharmacological activities. With the widespread popularity of natural products, such as antineoplastic drugs, AE has attracted much attention due to its remarkable antineoplastic activity on multiple tumor cells involving multi-channel mechanisms, including the disruption of cell cycle, induction of apoptosis, anti-metastasis, antiangiogenic, and strengthening of immune function. Experimental data have revealed AE as a potentially potent anti-cancer candidate. Despite this, the pharmaceutical application of AE is still in a fledging period as most research has concentrated on the elucidation of the molecular mechanism of action of existing treatments, rather than the development of novel formulations. Therefore, the present review summarizes the potential toxicity, molecular mechanism, pharmacokinetic characteristics, and pharmaceutical development of AE as an antineoplastic agent. This is based on its physicochemical properties, in an attempt to encourage further research on AE as a potential anti-cancer agent.

Anti-inflammatory properties of anthraquinones and their relationship with the regulation of P-glycoprotein function and expression

There is a growing interest in natural products that potentially have anti-inflammatory properties and inhibit P-glycoprotein (P-gp) function. In this report, we assessed the effects of anthraquinone derivatives from rhubarb on LPS-induced RAW 264.7 macrophages to determine their anti-inflammatory potential. The derivatives were also tested in Caco-2 cell lines to evaluate the inhibition of the drug efflux function of P-gp. The transport abilities were examined and the cellular accumulation of rhodamine-123 (R-123) was also measured. Electorphoretic mobility shift assay (EMSA) was performed to check the activator protein-1 (AP-1) DNA binding affinity. Five anthraquinones were tested to determine their inhibitory activities on NO production and the protein and mRNA expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Furthermore, the level of prostaglandin E(2) (PGE(2)) was determined in LPS-induced RAW264.7 macrophages. Emodin was found to be the most potent inhibitor, and it also reduced paw swelling in the mouse model of carrageenan-induced paw edema. In Caco-2 cells, emodin elevated the accumulation of R-123 and decreased the efflux ratio of R-123, which indicates the inhibition of P-gp function. The inhibition of COX-2 protein by emodin paralleled the decrease in P-gp expression. In addition, mitogen-activated protein kinase (MAPK) expression was decreased through the prevention of AP-1 DNA binding, which leads to downregulation in the expression of P-gp. Our data indicate that the decrease of P-gp expression is caused by the decreased expression of COX-2 through the MAPK/AP-1 pathway. Based on our results, we suggest that anti-inflammatory drugs with COX-2 inhibitory activity might be used to modulate P-gp function and expression.

Everted gut sac model as a tool in pharmaceutical research: limitations and applications

OBJECTIVES

This review discusses the limitations and applications of the everted gut sac model in studying drug absorption, metabolism, and interaction.

KEY FINDINGS

The mechanism of drug absorption, interaction and the effect of factors such as age, sex, species, chronic therapy, and disease state on drug absorption have been summarized. The experimental conditions and their effects on the outcomes of trials have been discussed also.

SUMMARY

The everted sac model is an efficient tool for studying in-vitro drug absorption mechanisms, intestinal metabolism of drugs, role of transporter in drug absorption, and for investigating the role of intestinal enzymes during drug transport through the intestine.

Dietary aloin, aloesin, or aloe-gel exerts anti-inflammatory activity in a rat colitis model

AIMS

Aloe has been a very popular folk remedy for inflammation-related pathological conditions despite the lack of studies reporting its efficacy in vivo. The present study evaluated the anti-inflammatory effects of aloe components (aloin, aloesin and aloe-gel) known to be biologically active in the rat model of colitis.

MAIN METHODS

Male Sprague Dawley rats were fed experimental diets for 2 weeks before and during the induction of colitis. Drinking water containing 3% dextran sulfate sodium (DSS) was provided for 1 week to induce colitis. At the end of the experimental period, clinical and biochemical markers were compared.

KEY FINDINGS

Plasma leukotriene B(4) (LTB(4)) and tumor necrosis factor-α (TNF-α) concentrations were significantly decreased in all groups supplemented with aloe components compared to the colitis control group (p<0.05). Animals fed both a 0.1% and 0.5% aloesin supplemented diet showed colonic myeloperoxidase (MPO) activities which were decreased by 32.2% and 40.1%, respectively (p<0.05). Colonic mucosa TNF-α and interleukin-1ß (IL-1β) mRNA expressions were significantly reduced in all animals fed aloin, aloesin, or aloe-gel (p<0.05).

SIGNIFICANCE

Dietary supplementation of aloe components ameliorates intestinal inflammatory responses in a DSS-induced ulcerative colitis rat model. In particular, aloesin was the most potent inhibitor. Further studies are required for a more complete understanding of the specific mechanism of the action of these supplements.