West African medicinal plants and their constituent compounds as treatments for viral infections, including SARS-CoV-2/COVID-19.

OBJECTIVES: The recent emergence of the COVID-19 pandemic (caused by SARS-CoV-2) and the experience of its unprecedented alarming toll on humanity have shone a fresh spotlight on the weakness of global preparedness for pandemics, significant health inequalities, and the fragility of healthcare systems in certain regions of the world. It is imperative to identify effective drug treatments for COVID-19. Therefore, the objective of this review is to present a unique and contextualised collection of antiviral natural plants or remedies from the West African sub-region as existing or potential treatments for viral infections, including COVID-19, with emphasis on their mechanisms of action. EVIDENCE ACQUISITION: Evidence was synthesised from the literature using appropriate keywords as search terms within scientific databases such as Scopus, PubMed, Web of Science and Google Scholar. RESULTS: While some vaccines and small-molecule drugs are now available to combat COVID-19, access to these therapeutic entities in many countries is still quite limited. In addition, significant aspects of the symptomatology, pathophysiology and long-term prognosis of the infection yet remain unknown. The existing therapeutic armamentarium, therefore, requires significant expansion. There is evidence that natural products with antiviral effects have been used in successfully managing COVID-19 symptoms and could be developed as anti-COVID-19 agents which act through host- and virus-based molecular targets. CONCLUSION: Natural products could be successfully exploited for treating viral infections/diseases, including COVID-19. Strengthening natural products research capacity in developing countries is, therefore, a key strategy for reducing health inequalities, improving global health, and enhancing preparedness for future pandemics.

Peristrophe bicalyculata (Retz) Nees contains principles that are cytotoxic to cancer cells and induce caspase-mediated, intrinsic apoptotic death through oxidative stress, mitochondrial depolarisation and DNA damage.

The plant Peristrophe bicalyculata (Retz) Nees is used for the treatment of cancer. While its leaf extracts have been shown to inhibit the growth of some cancer cells, there is little information supporting the constituents' anti-tumour potential. This study, therefore, investigated the effects of the plant's leaf extracts on cancer cells and the associated cellular/molecular mechanisms. Extracts were prepared using hexane (PBH), chloroform (PBC), ethyl acetate (PBE) and methanol (PBM) and constituents were identified by Liquid Chromatography-Mass Spectrometry (LC-MS). Their cytotoxic effects on human cervical (HeLa) and lung cancer (MRC5-SV2) cells were assessed using the MTT and LDH release assays. Reactive oxygen species (ROS) production was assessed using 2',7'-dichlorofluorescein diacetate (DCFDA) and mitochondrial membrane potential by staining with JC-1 (5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolyl-carbocyanine iodide). Caspase activation was determined using a Caspase-Glo-3/7 assay, and DNA damage by the Comet assay. Changes to mRNA expression were assessed using Quantitative Real-Time PCR. PBC, PBE and PBM reduced cell viability and induced LDH release, with IC50 values (48 h, MTT, in µg/ml), respectively, of 6.21 ± 0.70, 23.39 ± 3.92, and 22.43 ± 3.58 (HeLa); and 1.98 ± 0.33, 8.57 ± 1.91 and 28.24 ± 5.57 (MRC5-SV2). PBC induced ROS, while PBC, PBE and PBM impaired mitochondrial membrane potential and induced caspase 3/7 activation. PBC and PBE induced DNA damage, and PBE induced caspase-3 mRNA expression. Constituents of the extracts included derivatives of gallic acid, dipeptides, diterpenoids and flavones. We conclude that P. bicalyculata contains cytotoxic principles that could be potential leads for developing novel anti-cancer agents.

Potent Nrf2-inducing, antioxidant, and anti-inflammatory effects and identification of constituents validate the anti-cancer use of Uvaria chamae and Olax subscorpioidea.

BACKGROUND: Uvaria chamae (UC) and Olax subscorpioidea (OS) roots are included in traditional anti-cancer remedies and some studies have identified their chemopreventive/chemotherapeutic potential. This study aimed to identify some cellular/molecular mechanisms underlying such potential and the associated chemical constituents. METHODS: Effect on the viability of cancer cells was assessed using the Alamar Blue assay; ability to modulate oxidative stress was assessed using the 2',7'-dichlorofluorescein diacetate (DCFDA) assay; potential to modulate Nuclear factor erythroid 2-related factor like-2 (Nrf2) activity was assessed in the AREc32 luciferase reporter cell line; and anti-inflammatory effect was assessed using lipopolysaccharide-induced nitric oxide release model in the RAW264.7 cells (Griess Assay). Chemical constituents were identified through liquid chromatography-mass spectrometry (LC-MS). RESULTS: Extracts up to 100 µg/ml were non-toxic or mildly toxic to HeLa, AREc32, PC3 and A549 cells (IC50 > 200 µg/ml). Each extract reduced basal and peroxide-induced levels of reactive oxygen species (ROS) in HeLa cells. OS and UC activated Nrf2, with UC producing nearly four-fold induction. Both extracts demonstrated anti-inflammatory effects. Chamanetin, isochamanetin, isouvaretin, uvaricin I and other compounds were found in U. chamae root extract. CONCLUSION: As Nrf-2 induction, antioxidant and anti-inflammatory activities are closely linked with chemoprevention and chemotherapy of cancers, the roles of these plants in traditional anti-cancer remedies are further highlighted, as is their potential as sources of drug leads.

Anthelmintic activity and non-cytotoxicity of phaeophorbide-a isolated from the leaf of Spondias mombin L.

ETHNOPHARMACOLOGICAL RELEVANCE: Helminthosis (worm infection) is a disease of grazing livestock, with significant economic implications. Increasing resistance to existing synthetic anthelmintics used to control helminthosis and the unwanted presence of residues of the anthelmintics reported in meat and dairy products present a serious global health challenge. These challenges have necessitated the development of novel anthelmintics that could combat drug resistance and exhibit better safety profiles. Spondias mombin L. (Anacardiaceae) is a plant that has been used traditionally as a worm expeller. AIM OF STUDY: The aim of the work reported herein was to isolate and characterise anthelmintic compound(s) from S. mombin leaf, establishing their bioactivity and safety profile. MATERIALS AND METHODS: Adult Haemonchus placei motility assay was used to assess anthelmintic bioactivity. Bioassay-guided chromatographic fractionation of acetone extract of S. mombin leaf was carried out on a silica gel stationary phase. The structure of the compound was elucidated using spectroscopy (1H and 13C NMR) and Liquid Chromatography-Mass Spectrometry (LC-ESI-MS). Screening to exclude potential cytotoxicity against mammalian cells (H460, Caco-2, MC3T3-E1) was done using alamar blue (AB) and CellTitreGlo (CTG) viability reagents. RESULTS: The acetone extract yielded an active fraction 8 (Ethyl acetate: methanol 90:10; anthelmintic LC50: 3.97 mg/mL), which yielded an active sub-fraction (Ethyl acetate: Methanol 95:5; anthelmintic LC50: 53.8 µg/mL), from which active compound 1 was isolated and identified as phaeophorbide-a (LC50: 23.0 µg/mL or 38.8 µM). The compound was not toxic below 200 µM but weakly cytotoxic at 200 µM. CONCLUSIONS: Phaeophorbide-a (1) isolated from S. mombin leaf extract and reported in the plant for the first time in this species demonstrated anthelmintic activity. No significant toxicity to mammalian cells was observed. It therefore represents a novel anthelmintic pharmacophore as a potential lead for the development of novel anthelmintics.

Kola nut from Cola nitida vent. Schott administered to pregnant rats induces histological alterations in pups' cerebellum.

Kola nut (from Cola nitida) is popular in Nigeria and West Africa and is commonly consumed by pregnant women during the first trimester to alleviate morning sickness and dizziness. There is, however, a dearth of information on its effects on the developing brain. This study, therefore, investigated the potential effects of kola nut on the structure of the developing neonatal and juvenile cerebellum in the rat. Pregnant Wistar rats were administered water (as control) or crude (aqueous) kola nut extract at 400, 600, and 800 mg/kg body weight orally, from pregnancy to day 21 after birth. On postnatal days 1, 7, 14, 21 and 28, the pups were weighed, anaesthetised, sacrificed and perfused with neutral buffered formalin. Their brains were dissected out, weighed and the cerebellum preserved in 10% buffered formalin. Paraffin sections of the cerebellum were stained with haematoxylin and eosin for cerebellar cytoarchitecture, cresyl violet stain for Purkinje cell count, Glial Fibrillary Acidic Protein (GFAP) immunohistochemistry (IHC) for estimation of gliosis, and B-cell lymphoma 2 (Bcl-2) IHC for apoptosis induction. The kola nut-treated rats exhibited initial reduction in body and brain weights, persistent external granular layer, increased molecular layer thickness, and loss of Bergmann glia. Their Purkinje cells showed reduction in density, loss of dendrites and multiple layering, and their white matter showed neurodegeneration (spongiosis) and GFAP and Bcl-2 over-expression, with evidence of reactive astrogliosis. This study, therefore, demonstrates that kola nut, administered repeatedly at certain doses to pregnant dams, could disrupt normal postnatal cerebellar development in their pups. The findings suggest potential deleterious effects of excessive kola nut consumption on human brain and thus warrant further studies to understand the wider implications for human brain development.

Bioactivity and cytotoxicity profiling of vincosamide and strictosamide, anthelmintic epimers from Sarcocephalus latifolius (Smith) Bruce leaf.

ETHNOPHARMACOLOGICAL RELEVANCE: The leaf of Sarcocephalus latifolius is known to be used traditionally by the Fulanis in Nigeria to deworm animals. As helminthosis remains a major constraint to profitable livestock production worldwide, a precarious situation aggravated by the advent of resistant parasites, the discovery of new anthelmintics is a priority, necessitating exploration of medicinal plants for their anthelmintic principles. AIM OF THE STUDY: To identify and characterise compounds with anthelmintic activity from the leaf of Sarcocephalus latifolius. MATERIALS AND METHODS: Powdered S. latifolius leaves were extracted by successive maceration with n-hexane, chloroform and acetone. The dried extracts were evaluated for anthelmintic activity against Haemonchus placei adult worms, and the most active extract was subjected to bioassay-guided chromatographic separations. The isolated compounds were evaluated for cytotoxicity against the mammalian HeLa and MC3T3-E1 cell lines, using alamar blue and CellTitreGloTM to quantify cell viability. LC50 values were computed from the in vitro anthelmintic activity data by fitting to a non-linear regression equation (variable slope). Isolated compounds were characterized using spectroscopic and mass spectrometric analyses. RESULTS: Anthelmintic activity LC50 values for n-hexane, chloroform and acetone extracts were 47.85, 35.76 and 5.72 (mg/mL), respectively. Chromatographic separation of acetone extract afforded two bioactive epimers, identified as vincosamide (LC50 14.7 mg/mL) and strictosamide (LC50 12.8 mg/mL). Cytotoxicity evaluation showed that, below 200 µg/mL (400 µM), neither compound was toxic to the HeLa or MC3T3-E1 cells. CONCLUSION: Vincosamide and strictosamide could serve as novel scaffolds for the development of anthelmintic derivatives with improved potency and helminth selectivity.

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-ß-d-glucopyranoside, isoquercitrin (quercetin glucoside) and 5,7,3',4'-tetrahydroxy-flavonol-3-O-[ß-d-glucopyranosyl-(1→6)]-ß-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.

Pentagalloylglucose, isolated from the leaf extract of Anacardium occidentale L., could elicit rapid and selective cytotoxicity in cancer cells.

BACKGROUND: The leaf of Anacardium occidentale L. has been a component of many herbal recipes in South-Western Nigeria. The work reported herein, therefore, explored the phytochemical composition of this plant and the potential anti-cancer activity of an isolated chemical constituent. METHODS: Phytochemical methods (including chromatographic analysis) combined with spectroscopic and spectrometric analyses (IR, HRMS and NMR (1D and 2D)) were used to identify chemical constituents. Cytotoxic effects were determined using the MTT viability assay and bright-field imaging. Induction of oxidative stress was determined using the fluorescence-based 2',7'-dichlorofluorescein diacetate (DCFDA) assay. RESULTS: For the first time in the plant, Compound 1 was isolated from the leaf extract and identified as pentagalloylglucose. Compound 1 was significantly cytotoxic against the cancer cell lines HeLa (human cervical adenocarcinoma cell line) and MRC5-SV2 (human foetal lung cancer cell line), with IC50 of 71.45 and 52.24 µg/ml, respectively. The selectivity index (SI) for Compound 1 was 1.61 (IC50 against the normal human foetal lung fibroblast cell line MRC-5 was 84.33µg/ml), demonstrating better cancer cell-selectivity compared to doxorubicin with a SI of 1.28. The cytotoxic activity of Compound 1 in HeLa cells was also rapid, as shown by its concentration- and time-dependent 3 h and 6 h cytotoxicity profiles, an effect not observed with doxorubicin. Generation of reactive oxygen species at high concentrations of pentagalloylglucose to induce oxidative stress in cancer cells was identified as a mechanistic event that led to or resulted from its cytotoxicity. CONCLUSIONS: We suggest that pentagalloylglucose is selectively cytotoxic to cancer cells, and at high concentrations could exhibit pro-oxidant effects in those cells, as opposed to its general anti-oxidant effects in cells. Also, the presence of Compound 1 (pentagalloylglucose) in the plant and its cancer cell-selective cytotoxicity provide some rationale for the ethno-medicinal use of the plant's leaf extract for treating diseases associated with excessive cell proliferation. Further studies are required to dissect the molecular mechanisms and players differentially regulating the biphasic anti-oxidant and pro-oxidant effects of pentagalloylglucose in normal and cancer cells.

Antioxidative, antimitotic, and DNA-damaging activities of Garcinia kola stem bark, Uvaria chamae root, and Olax subscorpioidea root used in the ethnotherapy of cancers.

Garcinia kola (GK) stem bark, Uvaria chamae (UC) root, and Olax subscorpioidea (OS) root are components of various indigenous/traditional anticancer regimens. It is, therefore, possible that they might combat oxidative stress and impair cellular proliferation linked to carcinogenesis. In this study, we investigated the antioxidative, mito-depressive, and DNA-damaging activities of the three plant extracts in order to provide further mechanistic insights into their potential anticancer roles in documented cancer remedies that include them. Antioxidative properties were investigated in the 1,1-diphenyl-2-picrylhydrazyl (DPPH) and nitric oxide (NO) radical scavenging assays and an animal model of drug (cisplatin)-induced oxidative stress. The Allium cepa assay and the single cell gel electrophoresis (SCGE) assay were used to assess mito-depressive and DNA-damaging activities. GK and OS showed significantly higher antioxidant activities in the DPPH assay than ascorbic acid; OS had the lowest IC50 of the three plants in the NO assay, comparable to that of ascorbic acid. Pretreatment with the extracts produced an ameliorative and protective effect against the cisplatin-induced oxidative stress as shown by inhibition of lipid peroxidation and improved or restored reduced glutathione and superoxide dismutase levels. In the Allium test, the three extracts produced significant decreases in root growth and also significant cytotoxicity as evidenced by decreased mitotic index. Each of the extracts also showed significantly increased tail DNA (%) in the SCGE assay, indicating the significant DNA-damaging effect. Taken together, this study demonstrates the possible chemopreventive and chemotherapeutic potentials of the three study extracts, which may explain the roles of their source plants in traditional remedies in the therapy of cancers.

Identification of compounds with cytotoxic activity from the leaf of the Nigerian medicinal plant, Anacardium occidentale L. (Anacardiaceae).

Cancer is now the second-leading cause of mortality and morbidity, behind only heart disease, necessitating urgent development of (chemo)therapeutic interventions to stem the growing burden of cancer cases and cancer death. Plants represent a credible source of promising drug leads in this regard, with a long history of proven use in the indigenous treatment of cancer. This study therefore investigated Anacardium occidentale, one of the plants in a Nigerian Traditional Medicine formulation commonly used to manage cancerous diseases, for cytotoxic activity. Bioassay-guided fractionation, spectroscopy, Alamar blue fluorescence-based viability assay in cultured HeLa cells and microscopy were used. Four compounds, zoapatanolide A (1), agathisflavone (2), 1,2-bis(2,6-dimethoxy-4-methoxycarbonylphenyl)ethane (anacardicin, 3) and methyl gallate (4), were isolated, with the most potent being zoapatanolide A with an IC50 value of 36.2±9.8µM in the viability assay. To gain an insight into the likely molecular basis of their observed cytotoxic effects, Autodock Vina binding free energies of each of the isolated compounds with seven molecular targets implicated in cancer development (MAPK8, MAPK10, MAP3K12, MAPK3, MAPK1, MAPK7 and VEGF), were calculated. Pearson correlation coefficients were obtained with experimentally-determined IC50 in the Alamar blue viability assay. While these compounds were not as potent as a standard anticancer compound, doxorubicin, the results provide reasonable evidence that the plant species contains compounds with cytotoxic activity. This study provides some evidence of why this plant is used ethnobotanically in anticancer herbal formulations and justifies investigating Nigerian medicinal plants highlighted in recent ethnobotanical surveys.

Three indigenous plants used in anti-cancer remedies, Garcinia kola Heckel (stem bark), Uvaria chamae P. Beauv. (root) and Olax subscorpioidea Oliv. (root) show analgesic and anti-inflammatory activities in animal models.

ETHNOPHARMACOLOGICAL RELEVANCE: Phytochemicals with anti-oxidative and anti-inflammatory properties are known to inhibit tumour initiation, promotion and progression. Hence, there is an increasingly-convincing rationale for employing remedies containing those phytochemicals in the treatment of cancers and also as analgesic and anti-inflammatory adjuvants in therapy. The plants Garcinia kola Heckel (Clusiaceae), stem bark; Uvaria chamae P. Beauv. (Annonaceae), root; and Olax subscorpioidea Oliv. (Olacaceae), root, have been documented to be part of various indigenous anti-cancer regimens. AIM OF THE STUDY: To determine if the three plants exhibit significant anti-oxidative and anti-inflammatory properties. MATERIALS AND METHODS: Using established models, the analgesic and anti-inflammatory activities of the three plants were investigated. RESULTS: Pre-treatment with the plant extracts at 100, 200 and 400mg/kg produced inhibition of writhes; G. kola and U. chamae showed no significant effect on formalin-induced pain, but O. subscorpioidea produced inhibition in both phases of the formalin test. Similarly, while G. kola and U. chamae did not produce any significant inhibitory effect in the xylene-induced ear oedema model, the oedema was significantly reduced by O. subscorpioidea pre-treatment. However, all the three plants significantly inhibited the time-dependent increase in paw circumference in the carrageenan- and formaldehyde-induced rat paw oedema tests, with peak effects observed at 400mg/kg, 6h after the induction of oedema, comparable in some cases to the effects of two standard drugs, the non-steroidal anti-inflammatory drug diclofenac and the anti-inflammatory antibiotic doxycycline. CONCLUSION: We conclude that the three plant extracts possess analgesic and anti-inflammatory properties, thus providing a scientific rationale for their inclusion in some traditional anti-cancer regimens.