Antioxidative Activities and Phenolic Content of Extracts from Okra (Abelmoschus esculentus L.)

A Review: Pharmacological Activity and Phytochemical Profile of Abelmoschus esculentus (2010-2022)

Abelmoschus esculentus L. Moench (okra) which belongs to the family Malvaceae is a commonly consumed vegetable that consists of the seed component which is rich in polyphenolic compounds. The aim of this study is to highlight the chemical and biological diversity of A. esculentus. This plant contains many vitamins, minerals, proteins and carbohydrates in addition to flavonoids, terpenes, phenolic compounds and sterols. These variations in the chemical composition resulted in different therapeutic activities including antidiabetic, hypolipidemic, antioxidant, antimicrobial, anticancer, wound healing, hepatoprotective, immunomodulator, neuroprotective, and gastroprotective activities in addition to cardioprotective activity.

Effects of okra (Abelmoschus esculentus L.) leaves, fruits and seeds extracts on European sea bass (Dicentrarchus labrax) leukocytes, and their cytotoxic, bactericidal and antioxidant properties

Okra, Abelmoschus esculentus L., is a popular vegetable crop with many bioactive compounds. The in vitro immunostimulant, cytotoxic, bactericidal and antioxidant activities of ethanolic extracts obtained from different parts of okra (leaves, fruits, and seeds) were studied. Phytochemical screening of hydroalcoholic extracts of okra leaves, fruits and seeds revealed a significant content of total phenols and flavonoids. Significant effects on the activities of leukocytes in the head kidney of European sea bass (Dicentrarchus labrax) (viability, phagocytic ability and capacity, and respiratory burst), as well as on peroxidase leukocyte contents were detected after incubation for 24 h with different concentrations (0.01-1 mg mL^-1) of the extracts. The mean concentrations (0.1 and 0.5 mg mL^-1) of the different extracts increased the phagocytic ability and respiratory activity of head kidney leukocytes. However, the mean concentrations (0.1 mg mL^-1) of leaf and fruit extracts significantly decreased the peroxidase activity of leukocytes. In addition, all ethanolic okra extracts at higher concentrations (1 mg mL^-1) produced a marked reduction in the viability of the DLB-1 cell line compared to the viability recorded in the control samples. In addition, ethanolic extracts used at 0.5 and 1 mg mL^-1 had a significant cytotoxic effect on the viability of PLHC-1 cells. Finally, all doses of seed and leaf extracts at higher concentrations (0.5 and 1 mg mL^-1) showed significant bactericidal activity on two fish pathogenic bacteria, Vibrio anguillarum and V. harveyi strains. Finally, a remarkable antioxidant activity was detected on the ethanolic extracts. All these results point to their possible use as an alternative to chemical compounds in farmed fish.

Biological activity and development of functional foods fortified with okra (Abelmoschus esculentus)

The Abelmoschus esculentus plant, better known as okra, is an interesting crop from a nutritional standpoint. The okra plant is native to the African region but can now be found throughout tropical and subtropical areas of the world. This plant, known for its healing abilities, has been used as a traditional medicine to treat several diseases and external ailments, such as wounds or boils. This article reviews the potential health benefits from okra consumption, as well as the bioactive compounds that are suggested to be responsible. Furthermore, the okra plant and its derivatives have been evaluated in the formulation and manufacture of new functional food products. The latest advances in this direction, which includes characterizing the technical properties of functional foods fortified with okra are also presented in this review. A series of bioactive compounds such as flavonoids and catechins have been found in the okra plant, which were associated with numerous biological properties observed in research studies that reported potential anti-diabetic, anti-cancer, anti-hypertensive, and antimicrobial effects, among others, as a result of their consumption. These potential health benefits contribute to the development of new and useful functional foods, with okra (or its derivatives) being used as the highlighted ingredient.

Okra (Abelmoschus Esculentus) as a Potential Dietary Medicine with Nutraceutical Importance for Sustainable Health Applications

Recently, there has been a paradigm shift from conventional therapies to relatively safer phytotherapies. This divergence is crucial for the management of various chronic diseases. Okra (Abelmoschus esculentus L.) is a popular vegetable crop with good nutritional significance, along with certain therapeutic values, which makes it a potential candidate in the use of a variety of nutraceuticals. Different parts of the okra fruit (mucilage, seed, and pods) contain certain important bioactive components, which confer its medicinal properties. The phytochemicals of okra have been studied for their potential therapeutic activities on various chronic diseases, such as type-2 diabetes, cardiovascular, and digestive diseases, as well as the antifatigue effect, liver detoxification, antibacterial, and chemo-preventive activities. Moreover, okra mucilage has been widely used in medicinal applications such as a plasma replacement or blood volume expanders. Overall, okra is considered to be an easily available, low-cost vegetable crop with various nutritional values and potential health benefits. Despite several reports about its therapeutic benefits and potential nutraceutical significance, there is a dearth of research on the pharmacokinetics and bioavailability of okra, which has hampered its widespread use in the nutraceutical industry. This review summarizes the available literature on the bioactive composition of okra and its potential nutraceutical significance. It will also provide a platform for further research on the pharmacokinetics and bioavailability of okra for its possible commercial production as a therapeutic agent against various chronic diseases.

Isolation and Characterisation of Two Quercetin Glucosides with Potent Anti-Reactive Oxygen Species (ROS) Activity and an Olean-12-en Triterpene Glucoside from the Fruit of Abelmoschus esculentus (L.) Moench

Abelmoschus esculentus (Okra) is used in the traditional treatment of cancer, hyperlipidaemia and hyperglycaemia. We, therefore, investigated its composition and potential cytotoxic or antioxidant properties that might underlie its phytotherapeutic applications. Its methanolic fruit extract yielded compounds 1, 2 and 3, identified through NMR, UV and MS analyses as olean-12-en-3-O-β-d-glucopyranoside, isoquercitrin (quercetin glucoside) and 5,7,3',4'-tetrahydroxy-flavonol-3-O-[β-d-glucopyranosyl-(1→6)]-β-d-glucopyranoside (quercetin diglucoside), respectively. Following 48 h exposure, oleanene glucoside was mildly toxic to the HeLa and the MRC5-SV2 cancer cells, isoquercitrin was not toxic except at 100 μg/ml in HeLa, and quercetin diglucoside elicited no toxicity. In a 2',7'-dichlorofluorescein diacetate (DCFDA) assay of intracellular levels of reactive oxygen species (ROS), hydrogen peroxide increased ROS levels, an effect not affected by oleanene glucoside but protected against by isoquercitrin and quercetin diglucoside, with IC₅₀ values, respectively, of 2.7±0.5 μg/ml and 1.9±0.2 μg/ml (3 h post-treatment) and 2.0±0.8 μg/ml and 1.5±0.4 μg/ml (24 h post-treatment.) This is the first report of this oleanene skeleton triterpenoid in the plant. The work provides some insight into why the plant is included in remedies for cancers, cardiovascular complications and diabetes, and reveals it as a potential source of novel therapeutics.

Ethanolic extract of okra has a potential gastroprotective effect on acute gastric lesions in Sprague Dawley rats

Okra (Abelmoschus esculentus) has various bioactive components used for the treatment of different diseases such as gastritis and ulcers. This research aims to examine the anti-inflammatory and anti-ulcer attributes of okra extract against gastric lesions. Adult Sprague Dawley male albino rats were divided into five groups. The negative control (G1) received normal feed, positive control (G2) received ulcer-inducing drug aspirin 150 mg/kg of body weight (b.w), G3 group received reference drug omeprazole 20 mg/kg of b.w, G4 group received okra extract 250 mg/kg of b.w, and G5 group received 500 mg/kg of b.w. Acute gastric damage was induced in G1, G2, G3, and G4 using aspirin 150 mg/kg of b.w, during 14-day-long efficacy trials after that all the animals were sacrificed. Anti-ulcer parameters and histopathological analysis of stomachs were performed to evaluate the degree of recovery against tissue damage by the administration of okra extract. The obtained results indicated that the 500 mg/kg of b.w okra extract exerted a protective effect in aspirin-induced gastric ulcers by significantly (p < .05) reducing ulcer score, ulcer area, total acidity, and gastric volume, and significantly (p < .05) increasing gastric pH. Moreover, histopathological observation revealed that gastric mucosa was normal in G1, G3, G4, and G5; however, disruptions in the gastric epithelium were observed in G2. Congestion was observed in all groups except G1 and G5. Gastric pits and gastric glands were increased in size in G2 and G4. A higher concentration of okra extract (500 mg/kg of b.w) showed almost similar results when compared to the reference drug omeprazole.

Abelmoschus Esculentus (L.) Moench's Peel Powder Improves High-Fat-Diet-Induced Cognitive Impairment in C57BL/6J Mice

Okra peel exhibits numerous therapeutic effects. This study explores the potential ameliorative effects of okra peel powder on high-fat-diet (HFD)-induced hypercholesterolemia and cognitive deficits. Thirty-six C57BL/6J male mice were randomly divided into six groups (n = 6 per group): (i) control, mice fed with a normal diet; (ii) HFD, mice fed with HFD; (iii) HFD-SIM, mice fed with HFD and given simvastatin (20 mg/kg/day); (iv) HFD-OP1; (v) HFD-OP2; (vi) HFD-OP3, mice fed with HFD and okra peel (200, 400, or 800 mg/kg/day, respectively). Following 10 weeks of treatments, the mice were subjected to the Morris water maze (MWM). Parameters such as weekly average body weight, food intake, and blood lipid profiles were also recorded. The HFD group showed a profound increase in total cholesterol and low-density lipoprotein concentration compared to the control group. All okra-treated and HFD-SIM groups performed better than the HFD group during acquisition trials, whereas only the HFD-OP1 produced a significantly higher number of entries into the platform zone during the probe trial. In sum, all three okra doses improved the learning ability of the mice. However, only the lowest dose of okra significantly improved the spatial reference memory retention.

Antioxidant and Nephroprotective Effects of Okra Pods Extract (Abelmoschus esculentus L.) against Lead Acetate-Induced Toxicity in Mice

In this study, we determine the curative effects of okra pods (Abelmoschus esculentus L.) extract against lead acetate toxicity in mice kidney. n-Hexane, ethyl acetate, and methanol solvent were used for extracting okra pods. The role of the extract as an antioxidant was tested by DPPH and FRAP methods. The methanol extract was used for experiments in animals. A total of 30 male BALB/c mice were randomly divided into six equal groups: normal control, negative control (lead-induced), and treatment groups (lead-induced for 28 days and administration of methanol extract at doses of 50, 100, 200, and 400 mg/kg BW for the 28 days). The following were analyzed in all groups: activity of the antioxidant enzymes, namely, superoxide dismutase (SOD) and catalase (CAT); oxidant level, namely, malondialdehyde (MDA) and nitric oxide (NO); and markers of kidney injury, namely, blood urea nitrogen (BUN) and creatinine (Cre). Kidney histopathology was also evaluated. This study showed that the methanol extract showed the highest antioxidant activity (IC₅₀ is 35.21 µg/mL, and FRAP is 57.58 µM Fe^2+/g). The CAT and SOD activities increased significantly in okra-treated groups (P < 0.05). The okra administration groups experienced a significant decrease in MDA, NO, BUN, and Cre levels (P < 0.05). Thickness of the epithelial proximal tubule, diameter of the proximal tubule, and percentage of necrotic cells in proximal tubule decreased, but the diameter ratio of glomerular Bowman's capsule in mice treated with okra was optimally improved and repaired like normal control (P < 0.05). The results of this study reveal that methanol extract has a very strong antioxidant effect and can reduce the influence of toxicity induced by lead acetate in mice kidney.

Purple rice extract inhibits testosterone-induced rat prostatic hyperplasia and growth of human prostate cancer cell line by reduction of androgen receptor activation

The preventive effects of purple rice crude ethanolic extract (PRE) were firstly investigated on testosterone-induced benign prostatic hyperplasia (BPH) in castrated rats. As compared to vehicle-treated rats, lower prostate weights were found in the BPH rats that received PRE 1 g/kg bw. In addition, the PRE treatment down-regulated the androgen receptor (AR) expression in the dorsolateral prostate of those rats. In human prostate cancer cell line, LNCaP, PRE could reduce the cell growth, down-regulate the expression of AR and suppress prostate-specific antigen (PSA) secretion. Moreover, PRE also inhibited an activity of 5α-reductase from rat liver microsomes and the mutagenicity of Salmonella Typhimurium induced by standard mutagen. These results demonstrate that PRE altered testosterone-induced BPH in rats and retarded prostate cancer cell growth by modulating AR expression. It is therefore recommended that further investigation is undertaken into the chemopreventive potential of PRE in androgen-AR mediated diseases. PRACTICAL APPLICATIONS: This study revealed the mechanisms of purple rice extract on testosterone-induced rat benign prostatic hyperplasia. Such information, purple rice components show promise as an effective chemopreventive agent for prostatic hyperplasia prevention by alternating the influence of testosterone through its receptor. Thus, purple rice might be developed as food supplement for reduction of prostatic hyperplasia or cancer in elder men.

The chemical composition, nutritional value and antimicrobial properties of Abelmoschus esculentus seeds

Okra seeds present significant nutritional value and antimicrobial properties and could be proposed for innovative okra products and functional foods with antimicrobial and bioactive properties.

Phytochemical analysis, antioxidant, antistress, and nootropic activities of aqueous and methanolic seed extracts of ladies finger (Abelmoschus esculentus L.) in mice

Abelmoschus esculentus L. (ladies finger, okra) is a well-known tropical vegetable, widely planted from Africa to Asia and from South Europe to America. In the present study, we investigated the in vitro antioxidant capacity and in vivo protective effect of the aqueous and methanolic seed extracts of Abelmoschus esculentus against scopolamine-induced cognitive impairment using passive avoidance task and acute restraining stress-induced behavioural and biochemical changes using elevated plus maze (EPM) and forced swimming test (FST) in mice. Our results demonstrated that the pretreatment of mice with aqueous and methanolic seed extracts of Abelmoschus esculentus (200 mg/kg, p.o.) for seven days significantly (P < 0.01) attenuated scopolamine-induced cognitive impairment in the passive avoidance test. In addition, these extracts significantly reduced the blood glucose, corticosterone, cholesterol, and triglyceride levels elevated by acute restraint stress and also significantly increased the time spent in open arm in EPM and decreased the immobility time in FST. It has also been revealed that these extracts showed a significant antioxidant activity and no signs of toxicity or death up to a dose of 2000 mg/kg, p.o. These results suggest that the seed extracts of Abelmoschus esculentus L. possess antioxidant, antistress, and nootropic activities which promisingly support the medicinal values of ladies finger as a vegetable.

Ethyl acetate-n-butanol gradient solvent system for high-speed countercurrent chromatography to screen bioactive substances in okra

High-speed countercurrent chromatographic separation (HSCCC) possesses the property of zero-loss of sample, which is very useful for the screening of bioactive components. In the present study, the ethyl acetate-n-butanol gradient HSCCC solvent system composed of n-hexane-ethyl acetate-n-butanol-water was investigated for the screening of bioactive substances. To screen the antiproliferative compounds in okra extract, we used the stationary phase ethyl acetate-n-butanol-water (1:1:10) as the stationary phase, and eluted the antiproliferative components by 6-steps of gradient using mobile phases n-hexane-ethyl acetate (1:2), n-hexane-ethyl acetate (1:4), n-hexane-ethyl acetate (0:4), n-butanol-ethyl acetate (1:4) n-butanol-ethyl acetate (1:2), n-butanol-ethyl acetate (2:2), and n-butanol-ethyl acetate (2:1). The fractions collected from HSCCC separation with the gradient solvent system were assayed for antiproliferative activity against cancer cells. Bioactive components were identified: a major anti-cancer compound, 4'-hydroxy phenethyl trans-ferulate, with middle activity, and a minor anti-cancer compound, carolignan, with strong activity. The result shows that the gradient solvent system is potential for the screening of bioactive compounds from natural products.

Hypolipidemic activity of okra is mediated through inhibition of lipogenesis and upregulation of cholesterol degradation

Little is known about the hypolipidemic activity of okra; therefore, we investigated the hypolipidemic activity of okra and its interaction with gene expression of several key components involved in lipid homeostasis. Male C57BL/6 mice were randomly divided into three groups and fed with hyperlipidemic diet or two hyperlipidemic diets supplemented with 1% or 2% okra powder for eight weeks. Results demonstrated that okra dose-dependently decreased serum and hepatic total cholesterol and triglyceride, and enhanced fecal excretion of bile acids. Gene expression analysis revealed that okra upregulated cholesterol 7α-hydroxylase (CYP7A1) expression, downregulated expression of sterol regulatory element-binding protein 1c (SREBP1c) and fatty acid synthase (FAS), with no effect on sterol regulatory element-binding protein 2 (SREBP2), 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR), low-density lipoprotein receptor (LDLR) and carnitine palmitoyltransferase-1A (CPT1A). It was suggested that hypolipidemic activity of okra was mediated most likely by upregulation of cholesterol degradation through CYP7A1 and by inhibition of lipogenesis through SREBP1c and FAS. Okra raw and fractionated polysaccharide showed strong bile acid binding capacity in vitro, which may contribute to the hypolipidemic activity observed. In conclusion, okra has potential application in the management of hyperlipidemia and its associated metabolic disorders.

Polyphenol content and modulatory activities of some tropical dietary plant extracts on the oxidant activities of neutrophils and myeloperoxidase

Young leaves of Manihot esculenta Crantz (Euphorbiaceae), Abelmoschus esculentus (Malvaceae), Hibiscus acetosella (Malvaceae) and Pteridium aquilinum (Dennstaedtiaceae) are currently consumed as green vegetables by peoples in sub-Saharan Africa, Latin America, Asia and their migrants living in Western Europe. Sub-Saharan peoples use Manihot, Abelmoschus and Hibiscus also in the folk medicine to alleviate fever and pain, in the treatment of conjunctivitis, rheumatism, hemorrhoid, abscesses, ... The present study investigates the effects of aqueous extracts of those plants on the production of reactive oxygen species (ROS) and the release of myeloperoxidase (MPO) by equine neutrophils activated with phorbol 12-myristate 13-acetate (PMA). The ROS production was measured by lucigenin-enhanced chemiluminescence (CL), and the release of total MPO by an ELISA method. The study also investigates the effect of the extracts on the activity of MPO by studying its nitration activity on tyrosine and by using a new technique called SIEFED (Specific Immunological Extraction Followed by Enzymatic Detection) that allows studying the direct interaction of compounds with the enzyme. In all experiments, the aqueous extracts of the plants developed concentration-dependent inhibitory effects. A moderate heat treatment did not significantly modify the inhibitory capacity of the extracts in comparison to not heated ones. Total polyphenol and flavonoid contents were determined with an HPLC-UV/DAD analysis and a spectroscopic method using Folin-Ciocalteu reagent. Some polyphenols with well-known antioxidant activities (caffeic acid, chlorogenic acid, hyperoside, rosmarinic acid and rutin) were found in the extracts and may partly explain the inhibitory activities observed. The role of those dietary and medicinal plants in the treatment of ROS-dependent inflammatory diseases could have new considerations for health.

Antioxidant and antiradical activities of Manihot esculenta Crantz (Euphorbiaceae) leaves and other selected tropical green vegetables investigated on lipoperoxidation and phorbol-12-myristate-13-acetate (PMA) activated monocytes

Abelmoschus esculentus (Malvaceae), Hibiscus acetosella (Malvaceae), Manihot esculenta Crantz (Euphorbiaceae) and Pteridium aquilinum (Dennstaedtiaceae) leaves are currently consumed as vegetables by migrants from sub-Saharan Africa living in Western Europe and by the people in the origin countries, where these plants are also used in the folk medicine. Manihot leaves are also eaten in Latin America and some Asian countries. This work investigated the capacity of aqueous extracts prepared from those vegetables to inhibit the peroxidation of a linoleic acid emulsion. Short chain, volatile C-compounds as markers of advanced lipid peroxidation were measured by gas chromatography by following the ethylene production. The generation of lipid hydroperoxides, was monitored by spectroscopy using N-N'-dimethyl-p-phenylene-diamine (DMPD). The formation of intermediate peroxyl, and other free radicals, at the initiation of the lipid peroxidation was investigated by electron spin resonance, using α-(4-pyridyl-1-oxide)-N-tert-butylnitrone as spin trap agent. The ability of the extracts to decrease the cellular production of reactive oxygen species (ROS) in "inflammation like" conditions was studied by fluorescence technique using 2',7'-dichlorofluorescine-diacetate as fluorogenic probe, in a cell model of human monocytes (HL-60 cells) activated with phorbol ester. Overall the extracts displayed efficient concentration-dependent inhibitory effects. Their total polyphenol and flavonoid content was determined by classic colorimetric methods. An HPLC-UV/DAD analysis has clearly identified the presence of some polyphenolic compounds, which explains at least partially the inhibitions observed in our models. The role of these plants in the folk medicine by sub-Saharan peoples as well as in the prevention of oxidative stress and ROS related diseases requires further consideration.

Neuroprotective effects of quercetin, rutin and okra (Abelmoschus esculentus Linn.) in dexamethasone-treated mice

The administration of dexamethasone, a synthetic glucocorticoid receptor agonist, causes neuronal death in the CA3 layer of the hippocampus, which has been associated with learning and memory impairments. This study aimed to examine the ability of okra (Abelmoschus esculentus Linn.) extract and its derivatives (quercetin and rutin) to protect neuronal function and improve learning and memory deficits in mice subjected to dexamethasone treatment. Learning and memory functions in mice were examined using the Morris water maze test. The results showed that the mice treated with dexamethasone had prolonged water maze performance latencies and shorter time spent in the target quadrant while mice pretreated with quercetin, rutin or okra extract prior to dexamethasone treatment showed shorter latencies and longer time spent in target quadrant. Morphological changes in pyramidal neurons were observed in the dexamethasone treated group. The number of CA3 hippocampal neurons was significantly lower while pretreated with quercetin, rutin or okra attenuated this change. Prolonged treatment with dexamethasone altered NMDA receptor expression in the hippocampus. Pretreatment with quercetin, rutin or okra extract prevented the reduction in NMDA receptor expression. Dentate gyrus (DG) cell proliferation was examined using the 5-bromo-2-deoxyuridine (BrdU) immunohistochemistry technique. The number of BrdU-immunopositive cells was significantly reduced in dexamethasone-treated mice compared to control mice. Pretreatment with okra extract, either quercetin or rutin was found to restore BrdU-immunoreactivity in the dentate gyrus. These findings suggest that quercetin, rutin and okra extract treatments reversed cognitive deficits, including impaired dentate gyrus (DG) cell proliferation, and protected against morphological changes in the CA3 region in dexamethasone-treated mice. The precise mechanism of the neuroprotective effect of these plant extracts should be further investigated.