Polyphenolic compositions and in vitro angiotensin-I-converting enzyme inhibitory properties of common green leafy vegetables: A comparative study

A Critical Review of the Neuropharmacological Effects of Kratom: An Insight from the Functional Array of Identified Natural Compounds

Kratom (Mitragyna speciosa Korth. Havil) has been considered a narcotic drug for years, barred by the law in many parts of the world, while extensive research over the past few decades proves its several beneficial effects, some of which are still in ambiguity. In many countries, including Thailand, the indiscriminate use and abuse of kratom have led to the loss of life. Nonetheless, researchers have isolated almost fifty pure compounds from kratom, most of which are alkaloids. The most prevalent compounds, mitragynine and 7-hydroxy mitragynine, are reported to display agonist morphine-like effects on human μ-opioid receptors and antagonists at κ- and δ-opioid receptors with multimodal effects at other central receptors. Mitragynine is also credited to be one of the modulatory molecules for the Keap1-Nrf2 pathway and SOD, CAT, GST, and associated genes' upregulatory cascades, leading it to play a pivotal role in neuroprotective actions while evidently causing neuronal disorders at high doses. Additionally, its anti-inflammatory, antioxidative, antibacterial, and gastroprotective effects are well-cited. In this context, this review focuses on the research gap to resolve ambiguities about the neuronal effects of kratom and demonstrate its prospects as a therapeutic target for neurological disorders associated with other pharmacological effects.

Biochemistry of Amaranthus polyphenols and their potential benefits on gut ecosystem: A comprehensive review of the literature

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Amaranthus is phytonutrients-rich plant distributed worldwide and has been recognized as having medicinal value in traditional use against several diseases and conditions. There are a large amount of research data on the polyphenol profiles of Amaranthus plants and their links with potential benefits against gastrointestinal disorders.

AIM OF THE REVIEW

This review article aims to provide a comprehensive review of Amaranthus phenolic compounds and their microbial metabolites, as well as the biological and/or pharmacological effects of those compounds/metabolites.

METHODOLOGY

The relevant information about the genus Amaranthus was collected from various sources and databases, including Google Scholar, Google Books, PubMed, Web of Science, Scopus, Science Direct, and other internet sources. The World Flora Online (2021) database was used to verify the scientific names of the plants.

RESULTS

Comprehensive review of identified compounds in Amaranthus plants revealed the presence of phenolic acids, flavonoids, and coumarins in each part of the plants. The biotransformation by gut microbiota enzymes prominently produces diverse bioactive metabolites that are potentially active than their precursors. Lines of the evidence support the beneficial roles of Amaranthus extracts in several gastrointestinal diseases, particularly with the polar extracts of several plant parts. Dietary fibers in Amaranthus plants also coordinate the alteration of gut microbiota-related metabolisms and may be beneficial to certain gastrointestinal disorders in particular, such as constipation.

CONCLUSIONS

Amaranthus plants are rich in polyphenols and dietary fibers. Several microbial metabolites are biologically active, so alteration of gut microbiota is largely linked to the metabolic feature of the plants. Based on the evidence available to date, several Amaranthus plants containing a combination of phytonutrients, particularly polyphenols and dietary fibers, may be a promising candidate that is of interest to be further developed for use in the treatment of certain gastrointestinal conditions/disorders.

Telfairia occidentalis stimulates hepatic glycolysis and pyruvate production via insulin-dependent and insulin-independent mechanisms

Background

Telfairia occidentalis (TO), a plant consumed for its nutritional and medicinal values, exhibits hypoglycaemic effect. However, the metabolic fate of the glucose following TO-induced insulin secretion and consequent hypoglycaemia is not clear.

Objective

This study determined the effect of ethyl acetate and n-hexane fractions of TO leaf extracts on some biochemical parameters in the glucose metabolic pathway to explain the possible fate of blood glucose following TO-induced hypoglycaemia.

Methods

Eighteen male Wistar rats (180-200 g) divided into control, n-hexane TO fraction- and ethyl acetate TO fraction-treated groups (n = 6/group) were used. The control animals received normal saline while the treated groups received TO at 100 mg/kg for seven days. After 24 h following the last dose, the animals were anaesthetised using ketamine; blood samples were collected and livers harvested to determine some biochemical parameters.

Results

Ethyl acetate TO fraction significantly increased plasma insulin, liver glucokinase activity and plasma pyruvate concentration, but significantly decreased plasma glucose and liver glycogen, without significant changes in plasma lactate, glucose-6-phosphate, liver glucose-6-phosphatase and lactate dehydrogenase activities when compared with control. N-hexane TO fraction significantly reduced liver glucose-6-phosphatase activity and glycogen but significantly increased plasma pyruvate, without significant changes in plasma glucose, insulin, glucose-6-phosphate and lactate concentrations; and liver glucokinase and lactate dehydrogenase activities.

Conclusion

The present study showed that insulin-mediated TO-induced hypoglycaemia resulted in the stimulation of glycolysis and pyruvate production via insulin-dependent and insulin-independent mechanisms.

Starch composition, glycemic indices, antioxidant properties and carbohydrate hydrolyzing enzymes activities of African star apple fruit parts

Background

African star apple (Chrysophyllum albidum) is a traditonal fruit, which is predominant in tropical regions with the fruit parts consumed by the populace and used in folklore to manage diabetes. However, the likely activity mechanism is still undetermined. The current study examined and compared the inhibitory abilities of African star apple fruit parts on selected key enzymes related to diabetes mellitus in the pancreas tissue of rat.

Methods

Inhibitory effect of aqueous extract (1:10 w/v) of African star apple fruit parts (pulp, cotyledon, seed coat and pulp coat) on the activities of α-amylase, α-glucosidase, as well as their starch composition, phenolic constituents, estimated glycemic index, and antioxidant properties were assessed.

Results

The fruit parts showed low sugar, eGI, amylose, and amylopectin contents. The analysis also showed that the fruit parts inhibited α-glucosidase and α-amylase activities and exhibited antioxidant properties. Furthermore, the fruit parts contain high concentrations of beta-amyrin acetate, eleagine, epicatechin, epigallocatechin, skatole, stigmasterol and tetrahydro − 2- methylharman as revealed by HPLC-DAD.

Conclusion

The fruit part low estimated glycemic indices, strong antioxidant properties, inhibition of α-amylase and α-glucosidase activities exhibited might be related to the bioactive compounds contained in the extract. This could also be a potential mechanism for the use in the prevention and management of type-2 diabetes. Nevertheless, the African star apple pulp coat displayed the highest property in comparison to other parts of the fruit.

Extracts from Almond (Terminalia catappa) leaf and stem bark mitigate the activities of crucial enzymes and oxidative stress associated with hypertension in cyclosporine A-stressed rats

We investigated the effect of extracts from the leaf (ALE) and stem bark (ABE) of Almond tree on activities of some crucial enzymes [angiotensin-1 converting enzyme (ACE), arginase, acetylcholinesterase (AChE), phosphodiesterase-5 (PDE-5), adenosine deaminase (ADA), superoxide dismutase (SOD), catalase], and thiobarbituric acid reactive species (TBARS) associated with hypertension in normal adult male Wistar albino rats and Cyclosporine A (CsA)-stressed rats. The result revealed that CsA-stressed rats treated with captopril and extracts (ALE and ABE) had lowered ACE, arginase, AChE, PDE-5, ADA activities, and TBARS level, coupled with improved SOD and catalase activities compared with untreated CsA-stressed rats, which had reversed these biochemicals compared to normal rats. This suggests that the extracts could be explored to suppress hypertension and other cardiac injury known with CsA treatment; the potentials that could be linked with the constituent polyphenols. However, further studies including blood pressure should be determined to ascertain this claim. PRACTICAL APPLICATIONS: Drug-induced cardiotoxicity, hypertension, and organ damage are among the most common side effects of pharmaceutics. Therefore, it becomes imperative to find natural, effective, and alternative therapy with little or no side effect to combat drug toxicity. The use of Almond (leaf and stem bark) in folklore for the treatment/management of hypertension and other heart-related diseases without full scientific basis is on the increase. Hence, this study provides some biochemical evidences on the effect of Almond leaf and stem back extracts on crucial enzymes and oxidative stress markers involve in the incidence of hypertension in the course of Cyclosporine A administration. The findings of this study indicated that the studied plant materials could be promoted as nutraceutical agents to neutralize drug-induced cardiac injury and hypertension.

Chemical composition and in vitro antioxidant properties of water-soluble extracts obtained from Bangladesh vegetables

The aim of this study was to evaluate the nutritional value and antioxidant properties of aqueous extracts of some Bangladesh vegetables using fruits of ash gourd, bitter gourd, brinjal, okra, ridge gourd, snake gourd, and leaves of Indian spinach, kangkong, and stem amaranth. Proximate composition showed that the dried extracts were composed mainly of crude protein (14.6%-46.7%) and non-fibre carbohydrates (26.4%-53.5%). With the exception of stem amaranth, all the extracts had >40% DPPH radical scavenging ability at 0.5 mg/ml. In contrast metal chelation was lower, except in Indian spinach with ~46%. The ferric reducing antioxidant power (FRAP) was highest for the kangkong (10.9 mM Fe³⁺ reduced), which is similar to the 9.9 mM for butylated hydroxytoluene (BHT). All the extracts suppressed linoleic acid oxidation better than BHT within the first 5 days of the incubation period. We conclude that the Indian spinach, kangkong, and okra could be considered as the most promising sources of antioxidant compounds. PRACTICAL APPLICATIONS: Vegetables are commonly consumed as part of a regular diet but the high water and fiber contents usually mean that large quantities are required to provide long-term health benefits. Therefore, in this work, aqueous extracts of nine Bangladesh vegetables were prepared to provide a more concentrated form of nutrients and bioactive compounds. The extracts had strong nutritional value based on the high contents of crude protein, potassium, iron, and non-fibre carbohydrates. The high content of polyphenolic compounds in the extracts can also provide health benefits, which was demonstrated through strong free radical scavenging, metal chelation, ferric iron reduction, and inhibition of linoleic acid oxidation. These vegetable extracts have the potential to be used as sources of bioactive compounds to prevent or treat non-communicable diseases that are associated with high oxidative stress.

Evaluation of anti-proliferative activity of medicinal plants used in Asian Traditional Medicine to treat cancer

ETHNOPHARMACOLOGICAL RELEVANCE

The extensive biodiversity of plants in Southeast Asia and inadequate research hitherto warrant a continued investigation into medicinal plants. On the basis of a careful review of fresh medicinal plant usage to treat cancer from previous ethnobotanical interviews in Singapore and from the traditional uses of the indigenous plants, fresh leaves of seven locally grown medicinal plant species were evaluated for anti-proliferative activity.

AIM OF THE STUDY

To evaluate the anti-proliferative activity of local medicinal plant species Clausena lansium Skeels, Clinacanthus nutans (Burm. f.) Lindau, Leea indica (Burm. f.) Merr., Pereskia bleo (Kunth) DC., Strobilanthes crispus (L.) Blume, Vernonia amygdalina Delile and Vitex trifolia L.

MATERIALS AND METHOD

Fresh, healthy and mature leaves of the seven medicinal plants were harvested from various locations in Singapore and Malaysia for Soxhlet, ultrasonication and maceration extractions in three different solvents (water, ethanol and methanol). Cell proliferation assay using water soluble tetrazolium salt (WST-1) assay was performed on twelve human cancer cell lines derived from breast (MDA-MB-231, T47D), cervical (C33A), colon (HCT116), leukemia (U937), liver (HepG2, SNU-182, SNU-449), ovarian (OVCAR-5, PA-1, SK-OV-3) and uterine (MES-SA/DX5) cancer.

RESULTS

A total of 37 fresh leaf extracts from seven medicinal plants were evaluated for their anti-tumour activities in twelve human cancer cell lines. Of these, the extracts of C. lansium, L. indica, P. bleo, S. crispus, V. amygdalina and V. trifolia exhibited promising anti-proliferative activity against multiple cancer cell lines. Further investigation of selected promising leaf extracts indicated that maceration methanolic extract of L. indica was most effective overall against majority of the cancer cell lines, with best IC₅₀ values of 31.5 ± 11.4 µg/mL, 37.5 ± 0.7 µg/mL and 43.0 ± 6.2 µg/mL in cervical C33A, liver SNU-449, and ovarian PA-1 cancer cell lines, respectively.

CONCLUSION

The results of this study provide new scientific evidence for the traditional use of local medicinal plant species C. lansium, L . indica, P. bleo, S. crispus, V. amygdalina and V. trifolia in cancer treatment. These results highlight the importance of the upkeep of these indigenous plants in modern society and their relevance as resources for drug discovery.

Phenolic analysis and erectogenic function of African Walnut (Tetracarpidium conophorum) seeds: The impact of the seed shell on biological activity

This study investigated the erectogenic potential of African walnut seed (AWS). The extract from AWS cooked with/without shell interacted with phosphodiesterase-5 (PDE-5), arginase, angiotensin-I converting enzymes (ACE), and acetylcholinesterase (AChE); enzymes associated with erectile dysfunction (ED) and Fe²⁺ -induced malonaldehyde (MDA) production in the isolated penile tissue. The results showed that the extracts inhibited the enzymes and MDA production, but Walnut cooked with shell had the highest effect. This agreed with increased phenolic acids and flavonoids, found in the AWS cooked with the shell, compared with that cooked without shell. The inhibition of enzymes and antioxidative potentials could be among the possible mechanisms of actions of AWS in the management/treatment of ED. However, cooking walnut seed with the shell seem to be a contributing factor, as this could prevent possible leaching out of the phytochemicals that could be responsible for these biological effects. PRACTICAL APPLICATIONS: Walnut seed possesses a high content of phenolic compounds and inhibit enzymes relevant to the management of erectile dysfunction. Traditionally, Walnut seed is being cooked with/without the shell and consumed for the purpose of alternative medicine in folklore. Our investigation revealed the possible mechanism underlying the therapeutic effect Walnut seed in the management of ED, but the impact of the shell during cooking contributes to this effect. This result will inform the consumers and food scientist on the importance of cooking Walnut seed with the shell in order to maximize its nutraceutical values.

Polyphenol composition and antioxidant properties of vegetable leaf-fortified bread

The aim of this work was to determine the antioxidant properties of aqueous extracts of vegetable leaf-fortified bread as well as estimate the contents of polyphenolic compounds. Enriched bread was produced from wheat flour fortified at 1, 2, and 3% (w/w) with dried leafy vegetable powders from Amaranthus viridis, Solanum macrocarpon, and Telfairia occidentalis. Gallic acid was the most abundant soluble polyphenol in the control bread and the content in the control bread was significantly higher (p < 0.05) than in all the fortified bread samples. Fortification of bread especially at 3% level resulted in significantly (p < 0.05) higher concentrations of other polyphenols (myricetin, catechin, quercetin, and rutin) compared to the control bread. The fortified bread extracts had significantly (p < 0.05) more effective antioxidants than the control for DPPH radical scavenging activity, ferric iron reducing antioxidant power, metal chelation, and inhibition of linoleic acid peroxidation. PRACTICAL APPLICATIONS: Bread is one of the consumed foods and could be used as a suitable carrier of bioactive compounds. Leafy vegetables contain high levels of polyphenols that could provide beneficial effects by contributing to improved health status of consumers. Therefore, incorporation of leafy vegetables into leavened bread could provide a means of enhancing polyphenol consumption. In this work, we showed that soluble polyphenols were enriched in vegetable-fortified bread. The polyphenol-rich extracts of the fortified bread demonstrated better free radical scavenging and inhibition of unsaturated fatty acid oxidation activities than the regular bread. Therefore, regular consumption of vegetable leaf-fortified bread could lead to reduced oxidative stress and associated chronic diseases in human beings. The vegetable leaf fortification could also serve as a suitable means of enhancing the shelf life of wheat bread.