Aloe emodin, an anthroquinone from Aloe vera acts as an anti aggregatory agent to the thermally aggregated hemoglobin

Ponceau 4R induces aggregation in human serum albumin and morin acts as an anti-aggregating agent against dye induced aggregates

Aggregation of proteins occurs because of improper protein folding and is responsible for the development of multiple severe maladies such as Type II diabetes mellitus, Parkison's, Huntington's, and spongiform encephalopathy. In the current work, the interaction and aggregation of human serum albumin (HSA) in the presence of the food colorant Ponceau 4R at pH 2.0 was evaluated using multiple in-silico and multi-spectroscopic approaches. The UV-visible spectroscopy and steady state fluorescence spectroscopy confirmed the complex formation between Ponceau 4R and HSA. The binding of HSA to Ponceau 4R favored static mode of fluorescence quenching. The values of KSV and Kb were found to be 1.905 × 105 M-1 and 1.43 × 105 M-1 respectively. Ponceau 4R leads to modification of HSA microenvironment, as proven by three-dimensional fluorescence spectroscopy. Ponceau 4R in the concentration range (60-200 µM) triggered the aggregation of HSA at pH 2.0 as confirmed by turbidity and Rayleigh light scattering (RLS). The secondary structure alteration of human serum albumin (α-helical structure to cross-β conformation) induced by 140 µM Ponceau 4R was evaluated utilizing far-UV CD spectroscopy. This concentration of Ponceau 4R (140 µM) will now be further used in aggregation inhibition studies. The production of β-rich aggregates of HSA is further established by a red shift in the absorption maxima of the Congo red spectra. The scanning electron microscopy (SEM) results showed that HSA aggregates induced by Ponceau 4R were amorphous in nature. Molecular docking analysis showed that electrostatic interactions, hydrophobic interactions and hydrogen bonding were responsible for the Ponceau 4R-induced aggregation of HSA. Furthermore, morin further inhibits the Ponceau 4R-induced aggregation of HSA. The results from turbidity, RLS, and SEM analysis confirmed that aggregates of HSA induced by 140 µM Ponceau 4R became soluble when human serum albumin was pre-incubated with various amounts of morin (0-600 µM). Thus, we conclude that Ponceau 4R triggers the aggregation of human serum albumin, whereas morin is responsible for the inhibition of aggregation of protein.

Deciphering the the molecular mechanism of aloe-emodin in managing type II diabetes mellitus using network pharmacology, molecular docking, and molecular dynamics simulation approaches

Aloe-emodin (AE) has drawn interest due to its potential activity against type II diabetes mellitus (T2DM). However, the mechanisms underlying its antidiabetic activity are not well explored. Using network pharmacology, molecular docking and molecular dynamics simulation studies, we investigated its molecular mechanisms in the management of T2DM. Potential target genes of AE were predicted using the Swiss Target Prediction (http://www.swisstargetprediction.ch/) database. The GeneCards, OMIM and DisGeNET databases were used to compile a comprehensive list of genes associated with T2DM. A compound-disease-target network was constructed, and protein-protein interaction networks were analysed to identify hub genes. Finally, molecular docking and interaction analysis between AE and the identified proteins were performed using AutoDock tools. Investigation of AE targets and genes associated with T2DM identified 32 overlapping genes. Gene ontology studies revealed that AE may exert its anti-diabetic effects by modulating glucose metabolism and enhancing cellular response to glucose. Furthermore, KEGG pathway analysis suggested that AE influences these processes by targeting pathways related to apoptosis, insulin resistance, and T2DM signaling. The core target proteins identified were TNF, ALB, TP53, PPARG, BCL2, CASP3, and EGFR. AE interaction with each of these proteins exhibited a binding energy of > - 5 kcal/mol, with TNF showing the lowest binding energy (- 7.75 kcal/mol). Molecular dynamics simulation further validated the molecular docking results with TNF and EGFR exhibiting a strong affinity for AE and forming stable interactions. AE exerts its antidiabetic activity through multiple mechanisms, with the most significant being the amelioration of pancreatic β-cell apoptosis by binding to and inhibiting the actions of TNFα. Further cellular and molecular studies are needed to validate these findings.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40203-025-00337-1.

Plant anthraquinones: Classification, distribution, biosynthesis, and regulation

Anthraquinones are polycyclic compounds with an unsaturated diketone structure (quinoid moiety). As important secondary metabolites of plants, anthraquinones play an important role in the response of many biological processes and environmental factors. Anthraquinones are common in the human diet and have a variety of biological activities including anticancer, antibacterial, and antioxidant activities that reduce disease risk. The biological activity of anthraquinones depends on the substitution pattern of their hydroxyl groups on the anthraquinone ring structure. However, there is still a lack of systematic summary on the distribution, classification, and biosynthesis of plant anthraquinones. Therefore, this paper systematically reviews the research progress of the distribution, classification, biosynthesis, and regulation of plant anthraquinones. Additionally, we discuss future opportunities in anthraquinone research, including biotechnology, therapeutic products, and dietary anthraquinones.

The Anti-Diabetic Effects of Medicinal Plants Belonging to the Liliaceae Family: Potential Alpha Glucosidase Inhibitors

Background

Diabetes mellitus is a complex metabolic disorder that has an enormous impact on people's quality of life and health. Although there is no doubt about the effectiveness of oral hypoglycemic agents combined with lifestyle management in controlling diabetes, no individual has ever been reported to have been completely cured of the disease. Globally, many medicinal plants have been used for the management of diabetes in various traditional systems of medicine. A deep look in the literature has revealed that the Liliaceae family have been poorly investigated for their antidiabetic activity and phytochemical studies. In this review, we summarize medicinal plants of Liliaceae utilized in the management of type II diabetes mellitus (T2DM) by inhibition of α-glucosidase enzyme and phytochemical content.

Methods

The literature search was conducted using databases including PubMed, ScienceDirect, and Google Scholar to find the significant published articles about Liliaceae plants utilized in the prevention and treatment of antidiabetics. Data were filtered to the publication period from 2013 to 2023, free full text and only English articles were included. The keywords were Liliaceae OR Alliaceae OR Amaryllidaceae AND Antidiabetic OR α-glucosidase.

Results

Six medicinal plants such as Allium ascalonicum, Allium cepa, Allium sativum, Aloe ferox, Anemarrhena asphodeloides, and Eremurus himalaicus are summarized. Phytochemical and α-glucosidase enzymes inhibition by in vitro, in vivo, and human studies are reported.

Conclusion

Plants of Liliaceae are potential as medicine herbs to regulating PPHG and prevent the progression of T2DM and its complication. In silico study, clinical application, and toxicity evaluation are needed to be investigated in the future.

Aloe vera-An Extensive Review Focused on Recent Studies

Since ancient times, Aloe vera L. (AV) has attracted scientific interest because of its multiple cosmetic and medicinal properties, attributable to compounds present in leaves and other parts of the plant. The collected literature data show that AV and its products have a beneficial influence on human health, both by topical and oral use, as juice or an extract. Several scientific studies demonstrated the numerous biological activities of AV, including, for instance, antiviral, antimicrobial, antitumor, and antifungal. Moreover, its important antidepressant activity in relation to several diseases, including skin disorders (psoriasis, acne, and so on) and prediabetes, is a growing field of research. This comprehensive review intends to present the most significant and recent studies regarding the plethora of AV's biological activities and an in-depth analysis exploring the component/s responsible for them. Moreover, its morphology and chemical composition are described, along with some studies regarding the single components of AV available in commerce. Finally, valorization studies and a discussion about the metabolism and toxicological aspects of this "Wonder Plant" are reported.

Aloe Barbadensis Miller (Aloe Vera)

Aloe Barbadensis Miller (Aloe Vera, AV) is a widely recognized for its diverse health-promoting, skin care, and medicinal properties. This narrative review provides a comprehensive overview of AV's bioactive compounds, pharmacological activities, potential applications, its toxic and adverse effects, as well as the clinical evidence supporting AV's efficacy in disease prevention. AV contains over 200 bioactive compounds, with the inner clear gel of the leaves containing the majority of these compounds. These include phenolic acids (274.5-307.5 mg/100 g), flavonoids. (3.63-4.70 g/kg), polysaccharides (3.82-6.55 g/kg), saponins, alkaloids, terpenoids, and anthraquinone derivatives. Findings from clinical studies involving both humans and animals highlight the therapeutic potential of AV across diverse health domains. The studies demonstrate AV's efficacy in reducing blood glucose levels, exhibiting antioxidant and immunomodulatory effects, inducing apoptosis in cancer cells, protecting the liver from damage, and displaying antimicrobial properties. In the fields of dermatology and dentistry, AV has also been observed to promote skin and oral health. However, it is imperative to acknowledge potential risks, adhere to recommended dosages, and seek guidance from healthcare experts before employing AV as a natural therapeutic option. Moreover, considering safety concerns, further well-designed randomized controlled trials are necessary to substantiate the potential benefits of AV and comprehensively assess any associated risks.

Aloe-emodin: Progress in Pharmacological Activity, Safety, and Pharmaceutical Formulation Applications

Aloe-emodin (AE) is an anthraquinone derivative and a biologically active component sourced from various plants, including Rheum palmatum L. and Aloe vera. Known chemically as 1,8-dihydroxy-3-hydroxymethyl-anthraquinone, AE has a rich history in traditional medicine and is esteemed for its accessibility, safety, affordability, and effectiveness. AE boasts multiple biochemical and pharmacological properties, such as strong antibacterial, antioxidant, and antitumor effects. Despite its array of benefits, AE's identity as an anthraquinone derivative raises concerns about its potential for liver and kidney toxicity. Nevertheless, AE is considered a promising drug candidate due to its significant bioactivities and cost efficiency. Recent research has highlighted that nanoformulated AE may enhance drug delivery, biocompatibility, and pharmacological benefits, offering a novel approach to drug design. This review delves into AE's pharmacological impacts, mechanisms, pharmacokinetics, and safety profile, incorporating insights from studies on its nanoformulations. The goal is to outline the burgeoning research in this area and to support the ongoing development and utilization of AE-based therapies.

Acknowledging the use of botanicals to treat diabetic foot ulcer during the 21st century: A systematic review

BACKGROUND

Diabetic foot ulcer (DFU) is a serious health issue of diabetes mellitus that affects innumerable people worldwide. Management and treatment of this complication are challenging, especially for those whose immune system is weak.

AIM

To discuss the plants and their parts used to heal DFU, along with the mode of their administration in diabetic patients.

METHODS

The original articles on "the plants for the treatment of DFU" studied in clinical cases only were obtained from various bibliographic databases using different keywords.

RESULTS

The search resulted in 22 clinical cases records with 20 medicinal plants belonging to 17 families on 1553 subjects. The fruits and leaves were the most preferentially used parts for DFU treatment, regardless of whether they were being administered orally or applied topically. Of the 20 medicinal plants, 19 reported their effectiveness in increasing angiogenesis, epithelialization, and granulation, thus hastening the wound-healing process. The efficacy of these botanicals might be attributed to their major bioactive compounds, such as actinidin and ascorbic acid (in Actinidia deliciosa), 7-O-(β-D-glucopyranosyl)-galactin (in Ageratina pichinchensis), omega-3-fatty acid (in Linum usitatissimum), isoquercetin (in Melilotus officinalis), anthocyanins (in Myrtus communis), and plantamajoside (in Plantago major).

CONCLUSION

The validation of mechanisms of action underlying these phytocompounds contributing to the management of DFU can aid in our better understanding of creating efficient treatment options for DFU and its associated problems.

Glycation reduces the binding dynamics of aflatoxin B1 to human serum albumin: a comprehensive spectroscopic and computational investigation

Aflatoxin B1 (AFB1), a potent mutagen, is synthesized by Aspergillus parasiticus and Aspergillus flavus. Human serum albumin (HSA) is a globular protein with diverse roles. As AFB1 is ingested with food and is transported in the body via blood, it becomes pertinent to comprehend the effect of the binding of this toxin on the structure and conformation of HSA, which may help to get insight into the toxic effect of the exposure of the mycotoxin. In this study, multi-spectroscopic approaches have been used to evaluate the binding efficiency of AFB1 with both the native HSA (nHSA) and the glycated HSA (gHSA). Steady-state fluorescence spectroscopy reveals the static type of fluorescence quenching in the fluorescence emission spectra of nHSA and gHSA in the presence of AFB1. The binding constant (Kb) is calculated to be 6.88 × 104 M-1 for nHSA, while a reduced Kb value of 2.95 × 104 M-1 has been obtained for gHSA. The circular dichroism study confirms the change in the secondary structure of nHSA and gHSA in the presence of AFB1, followed by alterations in the melting temperature (Tm) of nHSA and gHSA. In silico computational findings envisaged the amino acid residues and bonds involved in the binding of nHSA and gHSA with AFB1. The comprehensive study analyzes the binding effectiveness of AFB1 with nHSA and gHSA and shows reduced binding of AFB1 to gHSA.Communicated by Ramaswamy H. Sarma.

Tuning the aggregation behavior of human insulin in the presence of luteolin: An in vitro and in silico approach

Protein misfolding and related formation of amyloid fibrils are associated with several conformational diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), prion diseases, and Diabetes mellitus, Type 2 (DM-II). Several molecules including antibiotics, polyphenols, flavonoids, anthraquinones, and other small molecules are implicated to modulate amyloid assembly. The stabilization of the native forms of the polypeptides and prevention of their misfolding and aggregation are of clinical and biotechnological importance. Among the natural flavonoids, luteolin is of great importance because of its therapeutic role against neuroinflammation. Herein, we have explored the inhibitory effect of luteolin (LUT) on aggregation of a model protein, human insulin (HI). To understand the molecular mechanism of the inhibition of aggregation of HI by LUT, we employed molecular simulation, UV-Vis, fluorescence, and circular dichroism (CD) spectroscopies along with the dynamic light scattering (DLS). The analysis of the tuning of the HI aggregation process by luteolin revealed that interaction of HI with LUT resulted in the decrease in binding of the various fluorescent dyes, such as thioflavin T (ThT) and 8-anilinonaphthalene-1-sulfonic acid (ANS) to this protein. Retention of the native-like CD spectra and resistance to the aggregation in the presence of LUT has confirmed the aggregation inhibitory potential of LUT. The maximum inhibitory effect was found at the protein-to-drug ratio of 1:12, and no significant change was observed beyond this concentration.

Synergy between machine learning and natural products cheminformatics: Application to the lead discovery of anthraquinone derivatives

Cheminformatics utilizing machine learning (ML) techniques have opened up a new horizon in drug discovery. This is owing to vast chemical space expansion with rocketing numbers of expected hits and lead compounds that match druggable macromolecular targets, in particular from natural compounds. Due to the natural products' (NP) structural complexity, uniqueness, and diversity, they could occupy a bigger space in pharmaceuticals, allowing the industry to pursue more selective leads in the nanomolar range of binding affinity. ML is an essential part of each step of the drug design pipeline, such as target prediction, compound library preparation, and lead optimization. Notably, molecular mechanic and dynamic simulations, induced docking, and free energy perturbations are essential in predicting best binding poses, binding free energy values, and molecular mechanics force fields. Those applications have leveraged from artificial intelligence (AI), which decreases the computational costs required for such costly simulations. This review aimed to describe chemical space and compound libraries related to NPs. High-throughput screening utilized for fractionating NPs and high-throughput virtual screening and their strategies, and significance, are reviewed. Particular emphasis was given to AI approaches, ML tools, algorithms, and techniques, especially in drug discovery of macrocyclic compounds and approaches in computer-aided and ML-based drug discovery. Anthraquinone derivatives were discussed as a source of new lead compounds that can be developed using ML tools for diverse medicinal uses such as cancer, infectious diseases, and metabolic disorders. Furthermore, the power of principal component analysis in understanding relevant protein conformations, and molecular modeling of protein-ligand interaction were also presented. Apart from being a concise reference for cheminformatics, this review is a useful text to understand the application of ML-based algorithms to molecular dynamics simulation and in silico absorption, distribution, metabolism, excretion, and toxicity prediction.

Anti-inflammatory Effect of Aloe vera Extract on Inflammatory Cytokines of Rats Fed with a High-Fat Diet (HFD)

Background: Cytokines are glycoprotein compounds with an important role in inducing and regulating inflammation. Objectives: The present study aimed to measure the effect of Aloe vera alcoholic extracts on inflammatory cytokines in rats fed with a high-fat diet. Methods: Forty adult male Wistar rats were purchased and randomly categorized into five groups, including two control groups (control and control fed a high-fat diet (HFD) and three experimental groups (high-fat diet + 150 mg/kg Aloe vera, high fat diet + 300 mg/kg Aloe vera, and high-fat diet + 600 mg/kg Aloe vera). The rats in the experimental groups received high-fat emulsion and three doses of Aloe vera for 60 days in the form of gavage. Following blood sampling, serum concentrations of tumor necrosis factor-alpha (TNF-α), transforming growth factor-beta (TGF-β), interleukin 6 (IL-6), and interferon-γ (INF-γ) were measured. Statistical analysis was administered using SPSS-20 software by ANOVA test. Mean comparisons were conducted via Duncan’s multiple range test at the 0.05 level of significance. Results: The findings showed that a high-fat diet (HFD) could increase the concentrations of inflammatory factors TNF-α and TGF-β (P < 0.05). Moreover, an increase in the concentration of inflammatory factor IL-6 was observed at P < 0.01. No significant effects were observed in the mean concentration of INF-γ in the study groups. The use of Aloe vera gel extract considerably reduced inflammatory factors TNF-α, TGF-β, and IL-6 in the Aloe vera extract-receiving groups. Conclusions: In general, the results of the present study revealed that Aloe vera alcoholic extract reduced inflammatory factors in the rats fed with a high-fat diet.

Effects of free soluble iron on thermal aggregation of hemoglobin

Aggregation of hemoglobin is implicated in the presentation of diseases like sickle cell disease and thalassemia. Hallmark of the disease being imbalance in the production of globin chains leading to aggregation of excess globin chains and aberrant hemoglobins associated with the disease, broadly categorized as hemoglobinopathy. We have studied thermal aggregation of hemoglobin at 70 °C and pH 6.5 using light scattering, flow cytometry and optical microscopy and tried to investigate effects of few abundant soluble metal ions on such aggregation. Our study indicate that only iron, both in Fe2+ and Fe3+ forms, could inhibit hemoglobin aggregation and the extent of inhibition was 60% in presence of 100 mgL-1 FeCl3. Similar effect was not seen in lysozyme aggregation. Metal ions such as, Cu2+, Zn2+ and Ni2+ also did not have any significant effects on hemoglobin aggregation. Results show this important chaperone like behavior of free iron affecting the kinetics and yield of the aggregation process which could have important consequence in the extent of severity of such hematological diseases.

Process, Outcomes and Possible Elimination of Aggregation with Special Reference to Heme Proteins; Likely Remediations of Proteinopathies

Protein folding is a natural phenomenon through which a linear polypeptide possessing necessary information attains three-dimension functionally active conformation. This is a complex and multistep process and therefore, the presence of several intermediary structures could be speculated as a result of protein folding. In in vivo, this folding process is governed by the assistance of other proteins called molecular chaperones and heat shock proteins. Due to the mechanism of protein folding, these intermediary structures remain major challenge for modern biology. Mutation in gene encoding amino acid can cause adverse environmental conditions which may result in misfolding of the linear polypeptide followed by the formation of aggregates and amyloidosis. Aggregation contributes to the pathophysiology of several maladies including diabetes mellitus, Huntington's and Alzheimer's disease. The propensity of native structure to form aggregated and fibrillar assemblies is a hallmark of amyloidosis. During aggregation of a protein, transition from α helix to β sheet is observed, and mainly β sheeted structure is visualised in a mature fibril. Heme proteins are very crucial for major life activities like transport of oxygen and carbon dioxide, synthesis of ATP, role in electron transport chain, and detoxification of free radicals formed during biochemical reactions. Any structural variation in the heme proteins may lead to a fatal response. Hence characterization of the folding intermediates becomes crucial. The characterization has been deciphered with the help of strong denaturants like acetonitrile and TFE. Moreover, possible role of elimination of these aggregates and prevention of protein denaturation is also discussed. Current review deals with the basic process and mechanism of the protein folding in general and the ultimate outcomes of the protein misfolding. Since Native conformation of heme proteins is essential for some vital activities as listed above, we have discussed possible prevention of denaturation and aggregation of heme proteins such as Hb, cyt c, catalase & peroxidase.

Pharmacological Update Properties of Aloe Vera and its Major Active Constituents

Aloe vera has been traditionally used to treat skin injuries (burns, cuts, insect bites, and eczemas) and digestive problems because its anti-inflammatory, antimicrobial, and wound healing properties. Research on this medicinal plant has been aimed at validating traditional uses and deepening the mechanism of action, identifying the compounds responsible for these activities. The most investigated active compounds are aloe-emodin, aloin, aloesin, emodin, and acemannan. Likewise, new actions have been investigated for Aloe vera and its active compounds. This review provides an overview of current pharmacological studies (in vitro, in vivo, and clinical trials), written in English during the last six years (2014–2019). In particular, new pharmacological data research has shown that most studies refer to anti-cancer action, skin and digestive protective activity, and antimicrobial properties. Most recent works are in vitro and in vivo. Clinical trials have been conducted just with Aloe vera, but not with isolated compounds; therefore, it would be interesting to study the clinical effect of relevant metabolites in different human conditions and pathologies. The promising results of these studies in basic research encourage a greater number of clinical trials to test the clinical application of Aloe vera and its main compounds, particularly on bone protection, cancer, and diabetes.

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.

Physiological serum copper concentrations found in malignancies cause unfolding induced aggregation of human serum albumin in vitro

Malignancies are characterized by several drastic metabolic changes, one of which is a progressive rise in the levels of serum copper. This rise in serum copper is documented across all malignancies and across malignancies in several species. This study aims to explore in vitro the effect of increased copper levels on the structure of the blood protein human serum albumin. Exposure of human serum albumin to physiologically relevant copper concentrations for 21 days resulted in structural modifications in the protein which were evident by changes in the intrinsic florescence. A loss of the predominantly alpha helical structure of human serum albumin was recorded along with a tendency to form protein aggregates. This aggregation was characterized by Thioflavin T and Congo Red assays. Rayleigh light scattering and turbidity assays confirmed aggregation. The aggregates were visually confirmed using transmission electron microscopy. This is the first report implicating increased copper levels as a cause of aggregation of blood proteins in malignancies. The physiological and biochemical implications of this phenomenon are discussed.

Optimized extraction process and identification of antibacterial substances from Rhubarb against aquatic pathogenic Vibrio harveyi

Response surface optimization was applied for the extraction of antibacterial substances from Rhubarb (ASR) against aquatic pathogenic Vibrio harveyi. Based on the experimental results of single factors, the optimal extraction conditions were determined by Box-Behnken design combined with response surface methodology with conditions: 100% ethanol as extraction solvent, liquid/material ratio of 29 mL/g and extraction temperature at 88 °C for 148 min. The factual value of inhibition zones can reach 21.31 ± 0.95 mm and is not different from the predicted value (21.74 mm), which showed that the response surface methodology applied to the extraction optimization of antibacterial substances from Rhubarb against V. harveyi is feasible. Moreover, the yield of ASR was 30.29 ± 2.27%. Five compounds, namely, aloe-emodin, rhein, emodin, chrysophanol and physcion, were identified in ASR by comparing the HPLC chromatogram of the reference mixtures and the sample. Contents of the five compounds were 0.68 ± 0.02, 0.24 ± 0.05, 0.78 ± 0.07, 6.68 ± 0.97 and 0.58 ± 0.15%, respectively. The minimal inhibitory concentration (MIC) values of ASR, aloe-emodin, rhein, emodin, chrysophanol and physcion were 0.625, 0.125, 0.015, > 1, > 1, and > 1 mg/mL, respectively, which indicated that aloe-emodin and rhein are the main antibacterial compounds of Rhubarb.