Enhancement of anti-inflammatory activity of Aloe vera adventitious root extracts through the alteration of primary and secondary metabolites via salicylic acid elicitation

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.

Ultrasound-Assisted Encapsulation of Anthraquinones Extracted from Aloe-Vera Plant into Casein Micelles

Aloe-vera extracted anthraquinones (aloin, aloe-emodin, rhein) possess a wide range of biological activities, have poor solubility and are sensitive to processing conditions. This work investigated the ultrasound-assisted encapsulation of these extracted anthraquinones (AQ) into casein micelles (CM). The particle size and zeta potential of casein micelles loaded with aloin (CMA), aloe-emodin (CMAE), rhein (CMR) and anthraquinone powder (CMAQ) ranged between 171–179 nm and −23 to −17 mV. The AQ powder had the maximum encapsulation efficiency (EE%) (aloin 99%, aloe-emodin 98% and rhein 100%) and encapsulation yield, while the whole leaf Aloe vera gel (WLAG) had the least encapsulation efficiency. Spray-dried powder (SDP) and freeze-dried powder (FDP) of Aloe vera showed a significant increase in size and zeta potential related to superficial coating instead of encapsulation. The significant variability in size, zeta potential and EE% were related to anthraquinone type, its binding affinity, and its ratio to CM. FTIR spectra confirmed that the structure of the casein micelle remained unchanged with the binding of anthraquinones except in casein micelles loaded with whole-leaf aloe vera gel (CMWLAG), where the structure was deformed. Based on our findings, Aloe vera extracted anthraquinones powder (AQ) possessed the best encapsulation efficiency within casein micelles without affecting its structure. Overall, this study provides new insights into developing new product formulations through better utilization of exceptional properties of casein micelles.

Biotic Elicitors in Adventitious and Hairy Root Cultures: A Review from 2010 to 2022

One of the aims of plant in vitro culture is to produce secondary plant metabolites using plant cells and organ cultures, such as cell suspensions, adventitious, and hairy roots (among others). In cases where the biosynthesis of a compound in the plant is restricted to a specific organ, unorganized systems, such as plant cell cultures, are sometimes unsuitable for biosynthesis. Then, its production is based on the establishment of organ cultures such as roots or aerial shoots. To increase the production in these biotechnological systems, elicitors have been used for years as a useful tool since they activate secondary biosynthetic pathways that control the flow of carbon to obtain different plant compounds. One important biotechnological system for the production of plant secondary metabolites or phytochemicals is root culture. Plant roots have a very active metabolism and can biosynthesize a large number of secondary compounds in an exclusive way. Some of these compounds, such as tropane alkaloids, ajmalicine, ginsenosides, etc., can also be biosynthesized in undifferentiated systems, such as cell cultures. In some cases, cell differentiation and organ formation is necessary to produce the bioactive compounds. This review analyses the biotic elicitors most frequently used in adventitious and hairy root cultures from 2010 to 2022, focusing on the plant species, the target secondary metabolite, the elicitor and its concentration, and the yield/productivity of the target compounds obtained. With this overview, it may be easier to work with elicitors in in vitro root cultures and help understand why some are more effective than others.

Root Cultures, a Boon for the Production of Valuable Compounds: A Comparative Review

Medicinal plants are an inevitable source of pharmaceutical drugs and most of the world population depends on these plants for health benefits. The increasing global demand for bioactive compounds from medicinal plants has posed a great threat to their existence due to overexploitation. Adventitious root and hairy root culture systems are an alternative approach to the conventional method for mass production of valuable compounds from medicinal plants owing to their rapid growth, biosynthetic and genetic stability. The main purpose of this review is to investigate the recent scientific research published worldwide on the application of adventitious and hairy root cultures to produce valuable compounds from medicinal plants. Furthermore, a comparison of adventitious root vs. hairy root cultures to produce valuable compounds has also been discussed. Various aspects such as medium composition, carbon source, pH, amount of macronutrients, optimization strategy, scale-up cultures, and use of biotic abiotic and nano-elicitors at various concentrations are the topic of discussion in this review. Several studies on adventitious and hairy root cultures of Polygonum multiflorum¸ Withania somnifera¸ Echinacea purpurea and Ajuga bracteosa have been discussed in detail which highlights the importance of elicitation strategies and bioreactor system, presenting commercial applications.

Methyl jasmonate-induced compositional changes of volatile organic compounds in Polygonum minus leaves

Polygonum minus Huds. is a medicinal aromatic plant rich in terpenes, aldehydes, and phenolic compounds. Methyl jasmonate (MeJA) is a plant signaling molecule commonly applied to elicit stress responses to produce plant secondary metabolites. In this study, the effects of exogenous MeJA treatment on the composition of volatile organic compounds (VOCs) in P. minus leaves were investigated by using a metabolomic approach. Time-course changes in the leaf composition of VOCs on days 1, 3, and 5 after MeJA treatment were analyzed through solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS). The VOCs found in MeJA-elicited leaves were similar to those found in mock-treated leaves but varied in quantity at different time points. We focused our analysis on the content and composition of monoterpenes, sesquiterpenes, and green leaf volatiles (GLVs) within the leaf samples. Our results suggest that MeJA enhances the activity of biosynthetic pathways for aldehydes and terpenes in P. minus. Hence, the production of aromatic compounds in this medicinal herb can be increased by MeJA elicitation. Furthermore, the relationship between MeJA elicitation and terpene biosynthesis in P. minus was shown through SPME-GC-MS analysis of VOCs combined with transcriptomic analysis of MeJA-elicited P. minus leaves from our previous study.

Medicinal Plants and Natural Products Used in Cataract Management

Cataract is the leading reason of blindness worldwide and is defined by the presence of any lens opacities or loss of transparency. The most common symptoms of cataract are impaired vision, decreased contrast sensitivity, color disturbance, and glare. Oxidative stress is among the main mechanisms involved in the development of age-related cataract. Surgery through phacoemulsification and intraocular lens implantation is the most effective method for cataract treatment, however, there are chances of serious complications and irreversible loss of vision associated with the surgery. Natural compounds consisting of antioxidant or anti-inflammatory secondary metabolites can serve as potential leads for anticataract agents. In this review, we tried to document medicinal plants and plant-based natural products used for cataract treatment worldwide, which are gathered from available ethnopharmacological/ethnobotanical data. We have extensively explored a number of recognized databases like Scifinder, PubMed, Science Direct, Google Scholar, and Scopus by using keywords and phrases such as “cataract”, “blindness”, “traditional medicine”, “ethnopharmacology”, “ethnobotany”, “herbs”, “medicinal plants”, or other relevant terms, and summarized the plants/phytoconstituents that are evaluated in different models of cataract and also tabulated 44 plants that are traditionally used in cataract in various folklore medical practices. Moreover, we also categorized the plants according to scientific studies carried out in different cataract models with their mechanisms of action.

Chrysophanol: A Natural Anthraquinone with Multifaceted Biotherapeutic Potential

Chrysophanol is a unique anthraquinone having broad-spectrum therapeutic potential along with ecological importance. It is the first polyketide that has been reported to be biosynthesized in an organism-specific manner. The traditional Chinese and Korean medicinal systems provide evidence of the beneficial effects of chrysophanol on human health. The global distribution of chrysophanol encountered in two domains of life (bacteria and eukaryota) has motivated researchers to critically evaluate the properties of this compound. A plethora of literature is available on the pharmacological properties of chrysophanol, which include anticancer, hepatoprotective, neuroprotective, anti-inflammatory, antiulcer, and antimicrobial activities. However, the pharmacokinetics and toxicity studies on chrysophanol demand further investigations for it to be used as a drug. This is the first comprehensive review on the natural sources, biosynthetic pathways, and pharmacology of chrysophanol. Here we reviewed recent advancements made on the pharmacokinetics of the chrysophanol. Additionally, we have highlighted the knowledge gaps of its mechanism of action against diseases and toxicity aspects.

Integrated Transcriptomic and Metabolomic Analysis of Five Panax ginseng Cultivars Reveals the Dynamics of Ginsenoside Biosynthesis

Panax ginseng C.A. Meyer is a traditional medicinal herb that produces bioactive compounds such as ginsenosides. Here, we investigated the diversity of ginsenosides and related genes among five genetically fixed inbred ginseng cultivars (Chunpoong [CP], Cheongsun [CS], Gopoong [GO], Sunhyang [SH], and Sunun [SU]). To focus on the genetic diversity related to ginsenoside biosynthesis, we utilized in vitro cultured adventitious roots from the five cultivars grown under controlled environmental conditions. PCA loading plots based on secondary metabolite composition classified the five cultivars into three groups. We selected three cultivars (CS, SH, and SU) to represent the three groups and conducted further transcriptome and gas chromatography-mass spectrometry analyses to identify genes and intermediates corresponding to the variation in ginsenosides among cultivars. We quantified ginsenoside contents from the three cultivars. SH had more than 12 times the total ginsenoside content of CS, with especially large differences in the levels of panaxadiol-type ginsenosides. The expression levels of genes encoding squalene epoxidase (SQE) and dammarenediol synthase (DDS) were also significantly lower in CS than SH and SU, which is consistent with the low levels of ginsenoside produced in this cultivar. Methyl jasmonate (MeJA) treatment increased the levels of panaxadiol-type ginsenosides up to 4-, 13-, and 31-fold in SH, SU, and CS, respectively. MeJA treatment also greatly increased the quantity of major intermediates and the expression of the underlying genes in the ginsenoside biosynthesis pathway; these intermediates included squalene, 2,3-oxidosqualene, and dammarenediol II, especially in CS, which had the lowest ginsenoside content under normal culture conditions. We conclude that SQE and DDS are the most important genetic factors for ginsenoside biosynthesis with diversity among ginseng cultivars.

Influence of Different Carbohydrates on Flavonoid Accumulation in Hairy Root Cultures of Scutellaria baicalensis

Carbohydrate sources play important roles in energy and growth of plants. Therefore, in this study, we investigated the optimal carbohydrate source in hairy root cultures (HRCs) of Scutellaria baicalensis infected with Agrobacterium rhizogenes strain R1000. The hairy roots were cultured in half-strength B5 liquid medium supplemented with seven different carbohydrates sources (sucrose, fructose, glucose, galactose, sorbitol, mannitol and maltose), each at a concentration of 100 mM, in order to identify the best carbon sources for the production of major flavones, such as wogonin, baicalin and baicalein. Sucrose, galactose and fructose markedly influenced the production of major flavones and were therefore chosen for subsequent experiments. HRC growth and flavone accumulation were examined following culture with 30, 100 and 150 mM sucrose, galactose and fructose, respectively. From these data, 150 mM sucrose was found to be the optimal carbon source for the enhancement of baicalein production and growth of S. baicalensis HRCs. Fructose caused the greatest increase in baicalin accumulation. Additionally, galactose was the optimal carbon source for wogonin production. These results provide important insights into the optimal growth conditions, particularly the appropriate carbohydrate source, for S. baicalensis.

Evaluation of biological properties and clinical effectiveness of Aloe vera: A systematic review

Aloe vera (蘆薈 lú huì) is well known for its considerable medicinal properties. This plant is one of the richest natural sources of health for human beings coming. The chemistry of the plant has revealed the presence of more than 200 different biologically active substances. Many biological properties associated with Aloe species are contributed by inner gel of the leaves. Most research has been centralized on the biological activities of the various species of Aloe, which include antibacterial and antimicrobial activities of the nonvolatile constituents of the leaf gel. Aloe species are widely distributed in the African and the eastern European continents, and are spread almost throughout the world. The genus Aloe has more than 400 species but few, such as A. vera, Aloe ferox, and Aloe arborescens, are globally used for trade. A. vera has various medicinal properties such as antitumor, antiarthritic, antirheumatoid, anticancer, and antidiabetic properties. In addition, A. vera has also been promoted for constipation, gastrointestinal disorders, and for immune system deficiencies. However, not much convincing information is available on properties of the gel. The present review focuses on the detailed composition of Aloe gel, its various phytocomponents having various biological properties that help to improve health and prevent disease conditions.

Elicitation: a tool for enriching the bioactive composition of foods

Elicitation is a good strategy to induce physiological changes and stimulate defense or stress-induced responses in plants. The elicitor treatments trigger the synthesis of phytochemical compounds in fruits, vegetables and herbs. These metabolites have been widely investigated as bioactive compounds responsible of plant cell adaptation to the environment, specific organoleptic properties of foods, and protective effects in human cells against oxidative processes in the development of neurodegenerative and cardiovascular diseases and certain types of cancer. Biotic (biological origin), abiotic (chemical or physical origin) elicitors and phytohormones have been applied alone or in combinations, in hydroponic solutions or sprays, and in different selected time points of the plant growth or during post-harvest. Understanding how plant tissues and their specific secondary metabolic pathways respond to specific treatments with elicitors would be the basis for designing protocols to enhance the production of secondary metabolites, in order to produce quality and healthy fresh foods.

Chrysophanol inhibits NALP3 inflammasome activation and ameliorates cerebral ischemia/reperfusion in mice

The most effective way to contain cerebral ischemic injury is reperfusion; however, reperfusion itself may result in tissue injury, for which inflammatory damage is one of the main causative factors. NALP3 inflammasome is a multiprotein complex. It consists of NALP3, ASC, and caspase-1, whose function is to switch on the inflammatory process. Chrysophanol is an extract from plants of Rheum genus and it possesses many pharmacological effects including its anti-inflammation activity. In this study, the effects of chrysophanol in cerebral ischemia/reperfusion and the potential mechanisms were investigated. Male CD1 mice were subject to transient middle cerebral artery occlusion (tMCAO). The NALP3 inflammasome activation status and its dynamic expression during the natural inflammatory response induced by tMCAO were first profiled. The neuroprotective effects of chrysophanol were then assessed and the potential mechanisms mediating the observed neuroprotection were then explored. Physical parameters including neurological deficit, infarct size, brain edema, and BBB permeability were measured at 24 h after tMCAO. Confocal microscopy, Western blotting, immunohistochemistry, and qRT-PCR techniques were utilized to analyze the expression of NALP3 inflammasome and IL-1β. Our results indicated that the brain tissue damage during cerebral ischemia/reperfusion is accompanied by NALP3 inflammasome activation. Chrysophanol could inhibit the activation of NALP3 inflammasome and protect cerebral ischemic stroke.