Phytochemical, Nutritional and Pharmacological Potentialities of Amaranthus spinosus Linn. : A review

https://doi.org/10.36547/ae.2021.3.2.49-59 Abstract Amaranthus spinosus has long been cultivated in tropical and subtropical areas of the world, especially in South Asia. It is well accepted by the people for its nutritional, pharmacological, phytochemical, and therapeutic functions in the human body. Tender stems, leaves, shoots, grains and sometimes the whole part of A. spinosus are eaten by humans or fed to farm animals, which contain carbohydrates, proteins, fats, fibers, vitamins, minerals and many other phytochemicals. This review aims to represent the nutritional and pharmacological activities of A. spinosus. To have a better understanding, we have discussed the nutritional status of A. spinosus, its available phytochemicals and their functional properties. Further, we demonstrated the potentiality of A. spinosus in various disease condition by discussing its functional activities, which includes antioxidant, antidiabetic, immuno-modulatory, hematological, gastrointestinal, anti-inflammatory, diuretic, antimicrobial, antimalarial, anti-ulcer, antipyretic, and antigenic activity. The availability of various important phytochemicals along with their functional properties make Amaranthus spinosus valuable for pharmaceuticals and nutraceuticals industry. Archives of Ecotoxicology, Vol. 3, No. 2, pp. 49-59, 2021


Introduction
Plant-based medicine is potentially the oldest form of medicine, some of which are not only used as medicine but also as nutritional victuals that showed the value of in-depth scientific evaluation. Amaranthus spinosus Linn.

Phytochemical constituents
Most of the phytochemicals of A. spinosus are found in the matured leaves, because maximum metabolism in plants occurs in matured stage. To obtain the extract, leaves are air-dried at room temperature and allowed for grinding and finally extract is collected by solvent extraction. The analysis of A. spinosus to determine its phytochemical contents are done by standard procedures  (Table 1). Amaranthus spinosus plant extract shows in vitro bioactivity because of the presence of innumerable phytochemical constituents (Maiyo et al., 2010). Moreover, biologically active phytochemical compounds largely contribute to the amelioration of public health (Table 2).

Nutritional and pharmacological activities
Several nutritional and pharmacological properties of A. spinosus are said to contain in traditional system. These have been scientifically substantiated by scientists which are discussed in the following sections.

The antioxidant activity
The antioxidant activity of A. spinosus is analyzed by nonenzymatic haemoglycosylation assay, which showed that secondary metabolites, named rutin and quercetin have inhibition tendency of haemoglycosylation up to 42% and 52% respectively ( Tanmoy  antioxidant activity is also examined by determining the oxidation of linoleic acid (Amabye, 2016). Some of the methods include DPPH or 2,2-diphenyl-1-picrylhydrazyl scavenging; superoxide anion radical scavenging; nitric oxide scavenging; hydroxyl free radical scavenging; and ABTS or 2,2´-azinobis-3ethyl-benzothiazoline-6-sulfonic acid radical scavenging assays (Kumar et al., 2010c). The antidiabetic activity A. spinosus has alpha amylase enzyme, which is a potential compound associated with carbohydrate digestion and glycemic balance.

Figure 4
Active phytochemicals of Amaranthus spinosus can reduce pancreatic cell damages. Insulin released from pancreatic cells stimulate both glucose uptake and glycogen formation, therefore, manifests antidiabetic activity by lowering the blood sugar level.

55
The immuno-modulatory activities A. spinosus has been demonstrated to possess immunological effects. It was determined by investigating the stimulatory effects of aqueous A. spinosus extract on spleen cells of female albino rats. The result showed that the extracts affiliate in stimulation of more B lymphocytes without increasing T lymphocytes level, and the immuno-stimulating effects of aqueous extract help B lymphocyte activation and proliferation of T-cell in vitro. Several studies substantiated that the extract of this plant can significantly escalate the splenocyte growth. The results also proved immuno-modulatory activity via direct in vitro B lymphocyte activation. A new immuno-stimulatory protein (GF1) having molecular mass of 313 kDa, which is thought to be a glycoprotein and heat labile, have 309 times higher immunostimulatory activity than that of water extract. This compound is highly potential for immune pharmacological use (Ganjare & Raut, 2019; Gotyal et al., 2016). Immuno-modulatory effects were also discovered using dexamethasone (DEX)-induced apoptosis in murine primary splenocytes and wild A. spinosus water extract. The result determined that A. spinosus water extract is capable of inhibiting the spontaneous, as well as the DEX induced apoptosis of splenocyte cells (Lin et al., 2008). Cell-mediated immune response by delayed type of hypersensitivity reaction to sheep RBC, and humoral immune response measured by hemagglutination antibody tire also corroborated the immunomodulatory activity. The result showed both immunomodulatory and immunosuppressant activity due to presence of various glycosides, steroids and other phytochemicals. Aqueous and alcoholic extracts showed more immuno-modulatory effect, and petroleum ether extract showed immunosuppressant effect (Tatiya et al., 2007).

The hematological activity
There has been a study on the effect of aqueous extract of leaves of A. spinosus on hematological parameters along with blood coagulation time in rat model, which showed little changes in the hematological activity and several enzymes level such as glutamate pyruvate transaminase, alkaline phosphatase and serum glutamate oxaloacetate transaminase (Akinloye & Olorede, 2000).
In another study, A. spinosus leaf extract was fed to growing pigs and administered to determine its effects on packed cell volume, white blood cell, red blood cell, and hemoglobin concentration. The result showed that there has been temporary decrease in levels of packed cell volumes, white blood cell, red blood cell and hemoglobin (Olufemi et al., 2003). Change in hematocellular constituents of albino rats using A. spinosus methanolic extract has been also been diagnosed, which showed that WBC, RBC and Hb level was highly restored after using A. spinosus methanolic extract (Gul et al., 2011).  et al., 2008).
In another study, 50% ethanolic extract of A. spinosus whole plant is evaluated for hepatoprotective and in vitro antioxidant activity. Standard gallic acid curve (0-1.0 mg/mL) and an antioxidant naming butylated hydroxy anisole showed both the total phenolic compounds level and the hepatotoxicity reduction capacity of ASE respectively. The result had shown the hepatotoxicity reducing capability of ASE is 2.26 times of BHA and total polyphenolics expressed as gallic acid equivalent was 336 ± 14.3 mg/g, which proved that ASE possesses significant hepatoprotective activity (Zeashan et al., 2009b).

The gastrointestinal activity
To determine the effect of A. spinosus in gastrointestinal tract, aqueous extract of A. spinosus was evaluated in mice using charcoal meal method. In the experiment, first group served as the basis of control, second group was made the standard, and the remaining 3-5 groups were fed A. spinosus aqueous extract at a dose of 50, 100 and 200 mg/kg weight of the mice respectively. Result of the experiment showed significant gastrointestinal motility at 100 mg/kg dose (Kumar et al., 2008).
Another in-vivo experiment in mice using crude extract of A. spinosus showed the laxative activity, which is partially intervened through the cholinergic action (Chaudhary et al.,  2012).

The anti-inflammatory activity
The anti-inflammatory activity of A. spinosus has been evaluated by an experiment in which the methanolic extract of A. spinosus was evaluated in various animal models. The extract inhibited the carrageenan inducing mice paw edema at a dose of 25-100 mg/kg and helped in inhibition of acetic acid inducing increased vascular permeability. Though the 50 and 100 mg/kg extract dose produced gastric erosion in rats along with indomethacin, 25 mg/kg extract along with tween-80 (polysorbate-80) did not show this effect in macroscopic evaluation. However, several experiments corroborated the anti-inflammatory properties of A. spinosus (Baral et al., 2010; Olajide et al., 2004).

The diuretic activity
To examine the diuretic activity of A. spinosus aqueous extract (ASAE) in rats, various doses of ASAE (200, 500, 1000, 1500 mg/kg), thiazide (10 mg/kg) and vehicle were fed to rats orally and their urine was collected and analyzed after 24 hours. The result showed that ASAE increased the concentrations of Na + , K + , Cland caused alkalization of urine. The report of this test proved that the A. spinosus may act as a thiazide-like diuretic, occupying the carbonic anhydrase inhibiting property (Amuthan et al.,  2012).

The antidepressant activity
By using Forced swimming test and Tail suspension test patterns, the anti-depressant activity of the methanolic extract of A. spinosus (MEAS) was examined, where reference standards were Escitalopram and Imipramine. The result of this experiment showed that the MEAS cause significant diminution of immobility in FST and TST comparing with Escitalopram and Imipramine (Kumar et al., 2014).

The Antimicrobial Activity
The A. spinosus has various pharmacologically active compounds, which shows antimicrobial activities in the disc 56 diffusion essay. Even though the trend for anti-fungal activity is same as of the anti-bacterial activity, the potency towards fungal strain is not as effective as for bacterial strains (Amabye, 2016). Terpenoids show antimicrobial activity against bacterium, fungus, virus and protozoa, and it is used to control Listeria monocytogenes. These terpenoid compounds demonstrate antimicrobial activity by lipophilic membrane disruption mechanism. If the hydrophilic behavior of ent-kaurene diterpenoid compounds can be increased by addition of methyl group, this will reduce the antimicrobial activity of these compounds. Flavonoids generally are known to show response against microbial infections. Flavonoids form complexes with extra-cellular and soluble proteins, as well as with bacterial cells in vivo. This is why flavonoids are also effective as antimicrobial agents (Maiyo et al., 2010).
Usage of dichloromethane extract of A. spinosus moderately shows antiprotozoal activity, especially on Blastocystis hominis when 2 mg/mL dose is introduced (Kawade et al., 2013).  The antimalarial activity Screening of A. spinosus shows impressive antimalarial activity in mice when evaluated by suppressive antimalarial assay for 4 days. A study on Plasmodium berghei berghei parasite strain, which was inoculated in mice, had been inhibited greatly by A. spinosus at elevated doses of the extract produced from the plant. With 100 mg/kg dose introduction, the inhibition percentage of parasitemia is low, but increased doses (300 mg/kg to 900 mg/kg) had given better inhibition percentage. Though the plant has lower antimalarial activity compared to malarial medicine chloroquine, it's parasitemia inhibition percentage can also be increased by introducing relatively higher doses (1000 mg/kg or more) (Hilou et al., 2006).

The anti-ulcer activity
In an interesting study on antiulcerogenic activity of A. spinosus, it was found out that A. spinosus possesses anti peptic ulcer activity when powdered leaves of A. spinosus is fed to gastric and duodenal ulcerated albino rats. The result shows that A. spinosus leaves can immensely protect ethanol inducing peptic or gastric ulcers, and cysteamine inducing gastric ulcers (duodenal ulcers). Though the anti-ulcer activity of A. spinosus showed less effect than a peptic ulcer drug, omeprazole, still it's role is crucial because of no known side effects or prolonged effects (Debiprasad et al., 2013).
In another study of anti-ulcer activity, 50% ethanolic extract of A. spinosus (ASE) whole plant was evaluated in rats. Induction of acute gastric mucosal lesions were monitored using three different assay models in the investigation. The result proved that ASE can significantly protect both ethanol induced and aspirin induced ulcer (Hussain et al., 2009). One of the important factors in ulcerogenesis is lipid peroxidation, and studies have substantiated that ASE can control this type of lipid peroxidation (Hussain et al., 2009; Sairam et al., 2002).
Search for new drugs of gastric ulcer led to another experiment on A. spinosus for its antiulcer activity. Result of the study showed that leaves of A. spinosus can prevent the loss of gastric protein, and the lipid peroxidation due to aspirin induced ulceration. Simultaneously, the leaves of this plant had increased gastric mucin, and showed cytoprotective effect against gastritis (Mitra et al., 2014).
More studies showed that roots and stems along with leaves of A. spinosus exhibits antiulcer activity in albino rats. The effect is prevalent against ethanol, HCl, Swimming stress (SS), pyloric ligation, and indomethacin inducing peptic or gastric ulcer. However, the result showed that utilization of powdered roots of A. spinosus with one of the ulcerogenic medicine can bring about more ulcerative protection in ethanol, HCl, SS, pyloric ligation, and indomethacin induced gastric ulcer than utilization of stems and leaves of A. spinosus (Mitra, 2013).

The antipyretic and antinociceptive activity
Antipyretic drugs can suppress the expression of COX-2 so that the higher temperature of the body is reduced through inhibition of PGE2 biosynthesis, whereas natural COX-2 inhibitors have fewer side effects (Luo et al., 2005). Methanol extract of A. spinosus shows antipyretic activity without inhibition of COX-2 expression when introduced to rats with yeast-induced elevated level of body temperature (Lakshman & Jayaveera, 2011). The antipyretic effect of A. spinosus is quite significant, and is similar to the paracetamol group when the introduced dose is 400 mg/kg (Bagepalli et al., 2011; Kumar et al., 2010c). In a study, 50% ethanolic extract of A. spinosus (ASE) had shown antinociceptive activity when introduced to male swiss albino rats by some methods, including acetic acid test, formalin test, tail suspension test and hot plate test. Result from the study had shown that ASE possesses the central as well as the peripheral antinociceptive activity, and significantly blocks pain in the first phase at higher dose of the extract (400 mg/kg). In the second 57 phase, ASE had blocked pain from inflammation with introduction of all the doses (Zeashan et al., 2009a).

The antigenic and allergenic activity
Pollen antigen standardization can assist in immunotherapy and diagnosis of allergenicity. A. spinosus is an essential aeroallergen and it has significance in type 1 hypersensitivity disorders. SDS-PAGE and IEF Analysis of five A. spinosus pollen samples showed that seven protein fractions have IgE binding capacities and nine proteins have allergenic properties (Singh & Dahiya, 2002).

Toxicities
The toxicity of A. spinosus was detected by scientists using OECD guidelines. By following this guideline, lethal dose 50% (LD50) was determined in a lab experiment using albino rats. The dose was 5 mg/kg, 50 mg/kg, 200 mg/kg, 300 mg/kg (later the dose was 250 mg/kg and 300 mg/kg for further study) with sufficient amount of water orally in a single dose. The result showed A. spinosus extract did not cause any toxicity in the animals up to 2000 mg/kg (Jhade et al., 2011; Mishra et al., 2012).
The genotoxicity of A. spinosus leaf extract was determined using meristematic root cells of Allium cepa and the antigenotoxic effects was determined by evaluating against H2O2-induced genetic damage in Allium cepa. The repot of this experiment manifested that higher dose of A. spinosus extract cause mitodepressive and clastrogenic effects, and lower dose of the A. spinosus extract reverts the clastrogenicity caused by H2O2. This clastrogenicity, which is induced by the A. spinosus extract demonstrates its genotoxicity. These results determined that A. spinosus extract has genotoxic as well as the antigenotoxic property (Prajitha & Thoppil, 2016).

Conclusion
A. spinosus is abundant in phytochemicals. This review of A. spinosus shows that it holds nutritional potential along with various pharmacological properties. Leaf extract of this plant shows antimicrobial activities, especially against food-borne pathogens, and some fungus. Though some detailed studies have been done on this plant, it has not been developed as a drug yet. More exhaustive data on A. spinosus is not available till now even though the study on this potential plant was started in 1970s through analyzing its grain composition. Data on extraction of super-critical fluid and fractionation, high pressure and extrusion processing techniques are unavailable. Yet the screening or analysis within last 3 decades revealed so many information of this plant, such as its application for high quality baked goods production, edible films, functional ingredients etc. More extensive research and analysis is required for the cataloging, documentation and commercialization of this plant, considering its potentialities.