Aloe polymannose enhances anti-coxsackievirus antibody titres in mice

New opportunities and perspectives on biosynthesis and bioactivities of secondary metabolites from Aloe vera

Historically, the genus Aloe has been an indispensable part of both traditional and modern medicine. Decades of intensive research have unveiled the major bioactive secondary metabolites of this plant. Recent pandemic outbreaks have revitalized curiosity in aloe metabolites, as they have proven pharmacokinetic profiles and repurposable chemical space. However, the structural complexity of these metabolites has hindered scientific advances in the chemical synthesis of these compounds. Multi-omics research interventions have transformed aloe research by providing insights into the biosynthesis of many of these compounds, for example, aloesone, aloenin, noreugenin, aloin, saponins, and carotenoids. Here, we summarize the biological activities of major aloe secondary metabolites with a focus on their mechanism of action. We also highlight the recent advances in decoding the aloe metabolite biosynthetic pathways and enzymatic machinery linked with these pathways. Proof-of-concept studies on in vitro, whole-cell, and microbial synthesis of aloe compounds have also been briefed. Research initiatives on the structural modification of various aloe metabolites to expand their chemical space and activity are detailed. Further, the technological limitations, patent status, and prospects of aloe secondary metabolites in biomedicine have been discussed.

A New Biomaterial Derived from Aloe vera-Acemannan from Basic Studies to Clinical Application

Aloe vera is a kind of herb rich in polysaccharides. Acemannan (AC) is considered to be a natural polysaccharide with good biodegradability and biocompatibility extracted from Aloe vera and has a wide range of applications in the biomedical field due to excellent immunomodulatory, antiviral, antitumor, and tissue regeneration effects. In recent years, clinical case reports on the application of AC as a novel biomedical material in tissue regenerative medicine have emerged; it is mainly used in bone tissue engineering, pulp-dentin complex regeneration engineering, and soft tissue repair, among other operations. In addition, multiple studies have proved that the new composite products formed by the combination of AC and other compounds have excellent biological and physical properties and have broader research prospects. This paper introduces the preparation process, surface structure, and application forms of AC; summarizes the influence of acetyl functional group content in AC on its functions; and provides a detailed review of the functional properties, laboratory studies, clinical cutting-edge applications, and combined applications of AC. Finally, the current application status of AC from basic research to clinical treatment is analyzed and its prospects are discussed.

Utilization of Aloe Compounds in Combatting Viral Diseases

Plants contain underutilized resources of compounds that can be employed to combat viral diseases. Aloe vera (L.) Burm. f. (syn. Aloe barbadensis Mill.) has a long history of use in traditional medicine, and A. vera extracts have been reported to possess a huge breadth of pharmacological activities. Here, we discuss the potential of A. vera compounds as antivirals and immunomodulators for the treatment of viral diseases. In particular, we highlight the use of aloe emodin and acemannan as lead compounds that should be considered for further development in the management and prevention of viral diseases. Given the immunomodulatory capacity of A. vera compounds, especially those found in Aloe gel, we also put forward the idea that these compounds should be considered as adjuvants for viral vaccines. Lastly, we present some of the current limitations to the clinical applications of compounds from Aloe, especially from A. vera.

In vitro and in vivo anti-Cryptosporidium and anti-inflammatory effects of Aloe vera gel in dexamethasone immunosuppressed mice

Cryptosporidiosis has been considered as a serious diarrheal disease, especially in immunodeficient patients, where they failed to clear the infection leading to several consequences of infection (i.e death). The role of cell mediated immunity in clearing the infection was demonstrated by the increased susceptibility of HIV/AIDS patients to infection. To date, no specific treatment has been proven for cryptosporidiosis in immunodeficient patients. The study aimed to evaluate the efficacy of Aloe vera gel for the treatment of cryptosporidiosis in immunocompetent and dexamethasone immunosuppressed mice in comparison to that of nitazoxanide. Mice were orally administrated with Aloe vera gel, in a daily dose of 250 mg/L in drinking water, for 14 consecutive days post infection. Parasitological, molecular and immunological measurements were recorded on the 7th, 14th, 21st and 32nd days post infection. Our in vitro results showed that 250 mg/L of prepared gel achieved the highest parasitic reduction. The body weights of Aloe vera treated mice on the 21st and 32nd day post infection, either in immunocompetent or immunosuppressed groups, were nearly the same as those of their corresponding control groups. Aloe vera gel succeeded in clearing cryptosporidiosis with a percent reduction of 100% in immunocompetent mice and 99.67% in immunosuppressed mice. The anti-inflammatory effect of Aloe vera reduced the levels of IFN-γ, IL-4, -6 and -17. The success of Aloe vera gel, in clearing cryptosporidiosis in immunosuppressed mice, was obvious either from the reduction of Cryptosporidium DNA or the oocysts in stool samples; and from the improvement of histopathological sections.

Biodegradable polymers for modern vaccine development

Most traditional vaccines are composed either of a whole pathogen or its parts; these vaccines, however, are not always effective and can even be harmful. As such, additional agents known as adjuvants are necessary to increase vaccine safety and efficacy. This review summarizes the potential of biodegradable materials, including synthetic and natural polymers, for vaccine delivery. These materials are highly biocompatible and have minimal toxicity, and most biomaterial-based vaccines delivering antigens or adjuvants have been shown to improve immune response, compared to formulations consisting of the antigen alone. Therefore, these materials can be applied in modern vaccine development.

Aloe polysaccharide protects skin cells from UVB irradiation through Keap1/Nrf2/ARE signal pathway

The aim of this study was to investigate if aloe polysaccharide (AP) has the repairing effect on ultraviolet b (UVB) injured nerve cells. The study applied BALB/c female mice as animal model, and NFG-activated PC12 cells as cell model of skin nerve. The cell viability was detected by MTT assay, and cell apoptosis was detected by TUNEL (TdT-mediated dUTP nick-end labeling) and Annexin-V/PI assay, and cell-cycle status in different groups were observed via flow cytometry (FCM). Enzyme-linked immunosorbent assay (ELISA) was applied to analyze oxidative stress and anti-oxidative ability in each group. Real-time PCR and western blot were used to detect the expression levels of Bax, Bcl-2, Caspase-3, Cyclin D1, Keap1, Nrf2, GCLC, and GSTP1. The results showed obvious inhibition of cell viability and cell-cycle progression and promotion of cell apoptosis by UVB irradiation through inducing oxidative stress. In AP treated groups, cell viability and proliferation could be markedly improved and cell apoptosis inhibited with higher anti-oxidative capability and up-regulated expression of Keap1, Nrf2, GCLC, and GSTP1. It suggested that AP was able to repair UVB induced injury on NGF activated skin neural cell PC12, probably through Keap1/Nrf2/ARE signal pathway.

Aloe Polysaccharides Inhibit Influenza A Virus Infection-A Promising Natural Anti-flu Drug

Influenza A virus causes periodic outbreaks and seriously threatens human health. The drug-resistant mutants have shown an epidemic trend because of the abuse of chemical drugs. Aloe polysaccharides (APS) extracted from Aloe vera leaves have evident effects on the therapy of virus infection. However, the activity of APS in anti-influenza virus has yet to be investigated. Here, we refined polysaccharides from A. vera leaf. In vitro test revealed that APS could inhibit the replication of a H1N1 subtype influenza virus, and the most obvious inhibitory effect was observed in the viral adsorption period. Transmission electron microscopy indicated that APS directly interacted with influenza virus particles. Experiments on PR8 (H1N1) virus infection in mice demonstrated that APS considerably ameliorated the clinical symptoms and the lung damage of the infected mice, and significantly reduced the virus loads and mortality. Our findings provided a theoretical basis for the development of novel natural anti-influenza agents.

Oral administration of Aloe vera gel, anti-microbial and anti-inflammatory herbal remedy, stimulates cell-mediated immunity and antibody production in a mouse model

Introduction

Aloe vera (L.) Burm. f. (Aloe barbadensis Mill) Liliaceae, succulent plant native to northern Africa, is presently cultivated in many regions of the world. Traditionally, its inner part of parenchyma, which contains aloe gel, was used for the treatment of minor wounds, inflammatory skin disorders, thermal and radiation burns and to alleviate chronic osteoarthritis pain. It also possesses some antimicrobial activity. Now, aloe gel is also increasingly consumed as a dietary supplement. Some data suggest its immunomodulatory properties.

The aim of the study

The aim of the study was to evaluate the influence of orally administered aloe gel on some parameters of cellular and humoral immunity viz. mitogen-induced proliferation of splenic lymphocytes and their chemokinetic activity, and anti-sheep red blood cells (SRBC) antibody production in Balb/c mice.

Results

Daily treatment of mice for 14 and 21 days with 50 µl or 150 µl of aloe gel dose resulted in enhanced chemokinetic activity and stronger response of their splenic lymphocytes to mitogen PHA and enhancement of anti-SRBC antibody production.

Carbohydrate-based immune adjuvants

The role for adjuvants in human vaccines has been a matter of vigorous scientific debate, with the field hindered by the fact that for over 80 years, aluminum salts were the only adjuvants approved for human use. To this day, alum-based adjuvants, alone or combined with additional immune activators, remain the only adjuvants approved for use in the USA. This situation has not been helped by the fact that the mechanism of action of most adjuvants has been poorly understood. A relative lack of resources and funding for adjuvant development has only helped to maintain alum's relative monopoly. To seriously challenge alum's supremacy a new adjuvant has many major hurdles to overcome, not least being alum's simplicity, tolerability, safety record and minimal cost. Carbohydrate structures play critical roles in immune system function and carbohydrates also have the virtue of a strong safety and tolerability record. A number of carbohydrate compounds from plant, bacterial, yeast and synthetic sources have emerged as promising vaccine adjuvant candidates. Carbohydrates are readily biodegradable and therefore unlikely to cause problems of long-term tissue deposits seen with alum adjuvants. Above all, the Holy Grail of human adjuvant development is to identify a compound that combines potent vaccine enhancement with maximum tolerability and safety. This has proved to be a tough challenge for many adjuvant contenders. Nevertheless, carbohydrate-based compounds have many favorable properties that could place them in a unique position to challenge alum's monopoly over human vaccine usage.

Polysaccharide biological response modifiers

Biological response modifiers (BRMs) are substances which augment immune response. BRMs can be cytokines which are produced endogenously in our body by immune cells or derivatives of bacteria, fungi, brown algae, Aloe vera and photosynthetic plants. Such exogeneous derivatives (exogeneous BRMs) can be nucleic acid (CpG), lipid (lipotechoic acid), protein or polysaccharide in nature. The receptors for these exogeneous BRMs are pattern recognition receptors. The binding of exogeneous BRMs to pattern recognition receptors triggers immune response. Exogenous BRMs have been reported to have anti-viral, anti-bacterial, anti-fungal, anti-parasitic, and anti-tumor activities. Among different exogeneous BRMs, polysaccharide BRMs have the widest occurrence in nature. Some polysaccharide BRMs have been tested for their therapeutic properties in human clinical trials. An overview of current understandings of polysaccharide BRMs is summarized in this review.

Antiviral Activities of Polysaccharides from Natural Sources

The ever increasing resistance of human pathogens to current anti-infective agents is a serious medical problem, leading to the need to develop novel antibiotic prototype molecules. In the case of viruses, the search for antiviral agents involves additional difficulties, particularly due to the nature of the infectious viral agents. Thus, many compounds that may cause the death of viruses are also very likely to injure the host cell that harbours them. Natural products are increasingly appreciated as leads for drug discovery and development. Screening studies have been carried out in order to find antiviral agents from natural sources, and the occurrence of antiviral activity in extracts of plants, marine organisms and fungi is frequent. The evidence indicates that there may be numerous potentially useful antiviral phytochemicals in nature, waiting to be evaluated and exploited. In addition, other plants, not previously utilized medicinally, may also reveal antivirals. Among natural antiviral agents, recent investigations have reconsidered the interest of phyto-polysaccharides, which act as potent inhibitors of different viruses. This chapter will illustrate a variety of antiviral polysaccharides from natural sources since 1990, with the aim of making this matter more accessible to drug development

Novel antiviral agents: a medicinal plant perspective

Several hundred plant and herb species that have potential as novel antiviral agents have been studied, with surprisingly little overlap. A wide variety of active phytochemicals, including the flavonoids, terpenoids, lignans, sulphides, polyphenolics, coumarins, saponins, furyl compounds, alkaloids, polyines, thiophenes, proteins and peptides have been identified. Some volatile essential oils of commonly used culinary herbs, spices and herbal teas have also exhibited a high level of antiviral activity. However, given the few classes of compounds investigated, most of the pharmacopoeia of compounds in medicinal plants with antiviral activity is still not known. Several of these phytochemicals have complementary and overlapping mechanisms of action, including antiviral effects by either inhibiting the formation of viral DNA or RNA or inhibiting the activity of viral reproduction. Assay methods to determine antiviral activity include multiple-arm trials, randomized crossover studies, and more compromised designs such as nonrandomized crossovers and pre- and post-treatment analyses. Methods are needed to link antiviral efficacy/potency- and laboratory-based research. Nevertheless, the relative success achieved recently using medicinal plant/herb extracts of various species that are capable of acting therapeutically in various viral infections has raised optimism about the future of phyto-antiviral agents. As this review illustrates, there are innumerable potentially useful medicinal plants and herbs waiting to be evaluated and exploited for therapeutic applications against genetically and functionally diverse viruses families such as Retroviridae, Hepadnaviridae and Herpesviridae

A glyconutritional mixture (Ambrotose®) provides some amelioration to mice with coxsackievirus-induced pancreatitis

Challenge of adolescent male CD-1 mice with a coxsackievirus B3 (CVB3) strain (CVB3m) induces mild to severe destruction of pancreatic acinar cells, but causes no deaths and does not induce hyperglycemia. A weekly parenteral (intraperitoneal) administration of a glyconutritional mixture (Ambrotose® to virus-challenged mice was assessed to determine if there were any benefits to recovery over an eight month period. Virus-challenged mice showed a significant weight loss over the initial five weeks of the experiment, but injection of Ambrotose® to similar virus-challenged mice restored the total body weight to levels found in normal mice. Normal mice given Ambrotose® exhibited a small weight gain. Mice given Ambrotose® showed reduced severity of pancreatitis, as evidenced by significant reductions in percentages of pancreatic acinar cells destroyed and proportion of sections of pancreata with destroyed acinar cells, compared to virus control-mice not injected with Ambrotose®. Statistical analyses of the extent of acinar cell pathology in all virus-challenged mice showed that Ambrotose® contributed significantly to recovery of the acinar cell population in virus-inoculated mice. Anti-viral antibody titers were not affected by Ambrotose® injections. One potential mechanism to explain the benefits derived from Ambrotose® injections came from studies of antioxidant levels of glutathione in splenic macrophages/monocytes. Whereas CVB3 challenge of mice reduced glutathione levels in the latter cells, Ambrotose® injections to virus-challenged mice restored glutathione levels to those found in normal mice. In summary, most but not all mice derived benefits from Ambrotose® injections, i.e. a reduction in pathology in the pancreas and restored levels of the antioxidant glutathione in macrophages/monocytes. Higher doses of Ambrotose® could provide greater benefits for more mice, a study for the future.