Elucidation of the possible mechanism of analgesic actions of butanol leaf fraction of Olax subscorpioidea Oliv

Evaluation of the anti-nociceptive profile of essential oil from Melissa officinalis L. (lemon balm) in acute and chronic pain models

ETHNOPHARMACOLOGICAL RELEVANCE

Melissa officinalis L. (Lamiaceae) is a medicinal plant native to Mediterranean regions and found in other parts of the world. Extracts and essential oil from this widely cultivated culinary medicinal herb are used in traditional medicine to manage a variety of disorders that include epilepsy and pain.

AIM OF THE STUDY

To assess the anti-nociceptive potentials of Melissa officinalis essential oil (MO) and probe the involvement of adrenergic, opioidergic, serotonergic and potassium adenosine triphosphate (KATP) mechanisms in its anti-nociceptive effects.

MATERIAL AND METHODS

We employed formalin-, acetic acid and hot plate-induced nociception to study the acute anti-nociceptive effects of MO. The sciatic nerve injury (CCI) model of neuropathic pain was utilized to study the anti-nociceptive effects of MO on chronic pain. Effects of MO on anxiety, cognitive deficits, oxidative stress and inflammation in the CCI rats were evaluated on elevated plus maze, open field test, novel object recognition, oxidative stress parameters and pro-inflammatory cytokines, respectively. The possible mechanism(s) of MO's anti-nociceptive effects were elucidated using prazosin, yohimbine, propranolol, glibenclimide, naloxone and metergoline, which are acknowledged antagonists for α1-, α2- and β-adrenergic, potassium adenosine triphosphate (KATP), opioidergic and serotonergic systems, respectively.

RESULTS

MO significantly attenuated acetic acid- and formalin-induced nociception; prolonged the mean reaction time of rats on hot plate before and following sciatic nerve chronic injury (CCI). MO ameliorated anxiety, cognitive deficits and oxidative stress, reduced pro-inflammatory cytokine levels and produced a near total restoration of injured sciatic nerves in CCI rats. Naloxone, metergoline and glibenclimide significantly blocked, while prazosin, yohimbine and popranolol failed to block the anti-nociceptive effects of MO in formalin-induced nociception.

CONCLUSIONS

MO contains biologically active compounds with potential anti-nociceptive properties that modulate KATP, opioidergic and serotonergic pathways. These support the development of bioactive compounds from MO as anti-nociceptive agents.

Cytotoxic triterpenoid saponins from the root of Olax subscorpioidea Oliv. (Olacaceae)

Bioactivity-guided phytochemical fractionation of the methanol extract of Olax subscorpioidea root has led to the isolation of six triterpenes. Three of these compounds are previously undescribed triterpenoid saponins: oleanolic acid 3-O-[α-L-rhamnopyranosyl-(1→3)-β-D-glucopyranosyl-(1 → 2)-6-O-methyl-β-D-glucuronopyranoside]-28-O-β-D-glucopyranosyl ester (2), oleanolic acid 3-O-[β-D-glucopyranosyl-(1 → 4)-β-D-glucopyranosyl-(1 → 3)-β-D-glucopyranoside] (3), and oleanolic acid 3-O-[β-D-glucopyranosyl-(1 → 4)-6-O-methyl-β-D-glucuronopyranoside] ester (5). Other reported known compounds include two triterpene glycosides: oleanolic acid 3-O-[β-D-glucopyranosyl-(1 → 4)-6-O-methyl-β-D-glucuronopyranoside]-28-O-β-D-glucopyranosyl ester (1) and oleanolic acid 3-O-[β-D-glucopyranosyl-(1 → 4)-β-D-glucuronopyranoside] (4); and a triterpene acid, oleanolic acid (6). The structures of these compounds were elucidated by spectroscopic means. The isolated compounds were tested against human cervical cancer (HeLa), colorectal cancer (Caco-2) and breast cancer (MCF-7) cell lines using the in vitro 3-[4,5-dimethylthiazole-2-yl] 3,5-diphenyltetrazolium bromide (MTT) assay, with vincristine as positive control. The cytotoxicity assay showed that compounds 3 and 5 exhibited significant inhibitory effects on the HeLa cell line, with IC50 values of 7.42 ± 0.34 μM and 10.27 ± 1.26 μM; and moderate effects on MCF-7 (IC50 values, 36.67 ± 1.23 μM and 43.83 ± 0.65 μM) and Caco-2 (IC50 values, 35.83 ± 0.55 μM and 39.03 ± 4.38 μM, respectively) cell lines. They were also more selectively cytotoxic than vincristine against the cancer cell lines, when compared with cytotoxicity against the normal lung cell line MRC5.

Bombax costatum enhances piroxicam's efficacy: Possible involvement of alpha-2 adrenergic receptor, opioidergic and arachidonic pathways

BACKGROUND

With increasing drug-herb combination and widespread use of Bombax costatum as analgesic in Africa, this research studies effects of Bombax costatum on piroxicam's efficacy and possible mechanisms of antinociception.

MATERIALS AND METHODS

In efficacy studies, four groups of mice were respectively treated with 1mL/kg distilled water, 400mg/kg Bombax costatum, 20mg/kg piroxicam and a combination of both. Acetic acid and hot plate were used to induce pain in mice while prostaglandin-E₂ and formalin were used to induce inflammation in rats. For mechanistic studies, different groups of mice were treated intraperitoneally with 2mg/kg naloxone, 1mg/kg yohimbine, 20mg/kg propranolol, 5mg/kg glibenclamide and 1mg/kg prazosin respectively. Two other groups were treated orally with 1mL/kg of the vehicle and 400mg/kg Bombax costatum respectively. 60minutes later, 10mL/kg of 0.6% acetic acid was administered via the intraperitoneal route and number of writhes were observed for 10minutes.

RESULTS

Concurrent administration of Bombax costatum and piroxicam decreased the number of writhes significantly (P≤0.001), increased reaction time with decreased paw diameter in comparison to control. Additionally, this drug-herb combination showed enhanced anti-nocipective efficacy than when administered singly. Also, pre-treatment with yohimbine and naloxone significantly (P≤0.01) inhibited the antinociceptive activities of Bombax costatum.

CONCLUSION

Bombax costatum posses antinociceptive and anti-inflammatory activities and may involve α-₂ adrenergic receptor, opioidergic and arachidonic pathways. In addition, Bombax costaum augments the efficacy of piroxicam and could be of clinical benefits if studied on man.

Ethnopharmacological uses, phytochemistry, pharmacology, and toxicology of Olax subscorpioidea Oliv (Olacaceae): a review

Background

The plant Olax subscorpioidea Oliv (Olacaceae) is a shrub that is widely available in Africa. It has been used in traditional medicine to treat various diseases including asthma, pain, inflammation, gastrointestinal and central nervous system (CNS) disorders, cough, diabetes mellitus, cancer, infectious diseases, hepatic diseases, and many other diseases. Several phytochemical and pharmacological investigations were conducted on this plant. However, comprehensive information on this medicinally important plant is not available in the literature. Therefore, in this review, we aimed to provide comprehensive and critical information on all the reported ethnomedicinal uses, phytochemistry, pharmacological activities, and potential toxicity of Olax subscorpioidea to highlight its therapeutic potentials based on traditional usage and identify research gaps as a basis for further investigations to develop novel therapeutic compounds.

Main body

The available information about the plant was retrieved from the online bibliographic databases (PubMed and Google Scholar) and published PhD dissertation using the search terms Olax subscorpioidea, traditional uses, ethnomedicinal uses, phytochemistry, pharmacology, toxicology, and safety. Phytochemical studies have shown that the plant contains several bioactive compounds such as rutin, morin, quercetin, caffeic acid, santalbic acid, n-hexadecanoic acid, squalene, nonacosane, hentriacontane, and many more compounds. Also, pharmacological investigations revealed that Olax subscorpioidea has antidepressant, antiepileptic, anti-Alzheimer’s, cytotoxic, antioxidant, antihyperlipidemic, analgesic, antiinflammatory, antiarthritic, antidiabetic, anticancer, antiulcer, antimicrobial, hepatoprotective, apoptotic, antiprotease, and other CNS effects.

Conclusion

Several pharmacological studies on Olax subscorpioidea have established its ethnopharmacological uses. However, there are limited phytochemical and pharmacological studies to validate other folkloric claims of the plant. Therefore, extensive phytochemical and further pre-clinical efficacy and safety evaluations to fully establish its therapeutic potentials and elucidate its mechanisms of pharmacological actions could be necessary.

Graphical abstract

The analgesic potential of glycosides derived from medicinal plants

Pain represents an unpleasant sensation linked to actual or potential tissue damage. In the early phase, the sensation of pain is caused due to direct stimulation of the sensory nerve fibers. On the other hand, the pain in the late phase is attributed to inflammatory mediators. Current medicines used to treat inflammation and pain are effective; however, they cause severe side effects, such as ulcer, anemia, osteoporosis, and endocrine disruption. Increased attention is recently being focused on the examination of the analgesic potential of phytoconstituents, such as glycosides of traditional medicinal plants, because they often have suitable biological activities with fewer side effects as compared to synthetic drugs. The purpose of this article is to review for the first time the current state of knowledge on the use of glycosides from medicinal plants to induce analgesia and anti-inflammatory effect. Various databases and search engines, including PubMed, ScienceDirect, Scopus, Web of Science and Google Scholar, were used to search and collect relevant studies on glycosides with antinociceptive activities. The results led to the identification of several glycosides that exhibited marked inhibition of various pain mediators based on different well-established assays. Additionally, these glycosides were found to induce most of the analgesic effects through cyclooxygenase and lipoxygenase pathways. These findings can be useful to identify new candidates which can be clinically developed as analgesics with better bioavailability and reduced side effects. Graphical abstract Analgesic mechanisms of plant glycosides.

Endogenous opiates and behavior: 2017

This paper is the fortieth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2017 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

Antinociceptive activity of methanol extract of Chlorophytum alismifolium tubers in murine model of pain: Possible involvement of α2-adrenergic receptor and KATP channels

The tubers of Chlorophytum alismifolium are used in Nigerian Herbal Medicine for the management of diabetes mellitus, painful and inflammatory conditions. The antinociceptive activity has been validated but the mechanism of this activity is yet to be explored. This study therefore, aimed to investigate the probable mechanism(s) of the antinociceptive activity of C. alismifolium tubers using experimental animal model of pain. HPLC and GC-MS analyses were carried out on the extract. Antinociceptive activity was investigated using acetic acid-induced writhing response test in mice. Three groups of mice were orally administered distilled water (10 ml/kg), C. alismifolium (400 mg/kg) and morphine (10 mg/kg) 60 min before administration of acetic acid and the resulting writhing were counted for 10 min. To establish the probable mechanism(s) of action of C. alismifolium, separate groups of animals were pretreated intraperitoneally with naloxone (2 mg/kg), prazosin (1 mg/kg), yohimbine (1 mg/kg), propranolol (20 mg/kg) and glibenclamide (5 mg/kg) 15 min before C. alismifolium administration. HPLC chromatogram of the extract revealed seventeen characteristic peaks with retention times ranging between 2.1 and 7.4 min. Administration of C. alismifolium significantly (p < 0.01) reduced the mean number of writhes compared to control group. Pretreatment with yohimbine and glibenclamide significantly (p < 0.05 and p < 0.01 respectively) reduced the antinociceptive activity of extract-alone treated group. However, pretreatment with prazosin, naloxone and propranolol showed no effect on its analgesic activity. The findings from this research revealed the possible involvement of α₂-adrenergic receptor and K_ATP channels in the antinociceptive activity of Chlorophytum alismifolium tuber extract.

HPLC-DAD finger printing, antioxidant, cholinesterase, and α-glucosidase inhibitory potentials of a novel plant Olax nana

BACKGROUND

The medicinal importance of a novel plant Olax nana Wall. ex Benth. (family: Olacaceae) was revealed for the first time via HPLC-DAD finger printing, qualitative phytochemical analysis, antioxidant, cholinesterase, and α-glucosidase inhibitory assays.

METHODS

The crude methanolic extract of O. nana (ON-Cr) was subjected to qualitative phytochemical analysis and HPLC-DAD finger printing. The antioxidant potential of ON-Cr was assessed via 1,1-diphenyl,2-picrylhydrazyl (DPPH), 2,2-azinobis[3-ethylbenzthiazoline]-6-sulfonic acid (ABTS) and hydrogen peroxide (H2O2) free radical scavenging assays. Furthermore, acetylcholinesterase (AChE) & butyrylcholinesterase (BChE) inhibitory activities were performed using Ellman's assay, while α- glucosidase inhibitory assay was carried out using a standard protocol.

RESULTS

The qualitative phytochemical analysis of ON-Cr revealed the presence of secondary metabolites like alkaloids, flavonoids, tannins, sterols, saponins and terpenoids. The HPLC-DAD finger printing revealed the presence of 40 potential compounds in ON-Cr. Considerable anti-radical activities was revealed by ON-Cr in the DPPH, ABTS and H2O2 free radical scavenging assays with IC50 values of 71.46, 72.55 and 92.33 μg/mL, respectively. Furthermore, ON-Cr showed potent AChE and BChE inhibitory potentials as indicated by their IC50 values of 33.2 and 55.36 μg/mL, respectively. In the α-glucosidase inhibition assay, ON-Cr exhibited moderate inhibitory propensity with an IC50 value of 639.89 μg/mL.

CONCLUSIONS

This study investigated Olax nana for the first time for detailed qualitative phytochemical tests, HPLC-DAD finger printing analysis, antioxidant, anticholinesterase and α-glucosidase inhibition assays. The antioxidant and cholinesterase inhibitory results were considerable and can provide scientific basis for further studies on the neuroprotective and anti-Alzheimer's potentials of this plant. ON-Cr may further be subjected to fractionation and polarity guided fractionation to narrow down the search for isolation of bioactive compounds.

Pharmacological mechanisms involved in the analgesia induced by ethanol extract of Hybanthus enneaspermus leaves

Background

Hybanthus enneaspermus (HE) leaves are being used traditionally to relieve pain, and scientific studies have demonstrated their analgesic potential. This study attempted to elucidate the pharmacological mechanism(s) involved in the analgesic action of ethanol extract of H. enneaspermus leaves (EEHE).

Materials and methods

Forty-two male Wistar rats were separately randomized into seven groups (n=6 rats in each group) for tail immersion and formalin tests. Group I (control) received distilled water (10 mL/kg) while groups II and III received acetaminophen (the reference drug, 100 mg/kg ip) and EEHE (1000 mg/kg po), respectively. Groups IV–VII were pretreated with cimetidine (50 mg/kg ip), naloxone (5 mg/kg ip), propranolol (0.15 mg/kg ip), and prazosin (0.15 mg/kg ip), respectively, 1 hour before EEHE (1000 mg/kg po) treatment.

Results

The EEHE-induced increase in tail-flick latency was reduced by blockade of histamine and adrenergic receptors but prevented by blockade of opiate receptor in the tail-flick test. However, the EEHE-induced decrease in paw licking time was prevented only by blockade of opiate receptor but unaffected by histamine and adrenergic receptors blockers.

Conclusion

These findings suggest that the analgesic effect of EEHE in different pain types may involve different neural mechanisms and that the opioidergic pathway contributes more to EEHE-induced analgesia than the other pathways.