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.

Leishmanicidal activity of the root bark of Erythrophleum Ivorense (Fabaceae) and identification of some of its compounds by ultra-performance liquid chromatography quadrupole time of flight mass spectrometry (UPLC-QTOF-MS/MS).

ETHNOPHARMACOLOGICAL RELEVANCE: Leishmaniasis is one of the neglected tropical disease caused by a protozoan of the genus Leishmania transmitted by sandflies. High cost and lack of oral formulation of existing drugs, rapid developments of resistance by the parasite coupled with serious side effects require new treatments to augment or replace currently available therapies. The major merits of herbal medicine seem to demonstrate perceived efficacy, low incidence of serious adverse effects and low cost. Erythrophleum plants possess beneficial biological properties and, as such, characterization of the bioactive components of these plants is imperative. Previous work has shown an overwhelming presence of cassaine alkaloids in these plants. However, amongst these plants, the African based specie (Erythrophleum ivorense) is the least studied. OBJECTIVE: In the current study, the in vitro anti-leishmanial activity of the crude extract, its fractions and isolated compounds were evaluated using direct counting assay of promastigotes of Leishmania donovani using amphotericin B as positive control. MATERIALS AND METHODS: The anti-leishmanial activity of E. ivorense extract was evaluated in vitro against the promastigote forms of Leishmania Donovani using a direct counting assay based on growth inhibition. Different crude extracts from ethyl acetate, pet-ether, and methanol as well as pure isolated compounds of E. ivorense: Erythroivorensin, Eriodictyol and Betulinic acid were screened. To know the possible components of the active methanolic extract, attempt was made to elucidate the extract using ultra-performance liquid chromatography quadrupole time of flight mass spectrometry (UHPLC-QTOF-MS/MS). RESULTS: This afforded a weak pet-ether fraction, a moderately active ethyl acetate fraction and a significantly active methanol fraction (IC50 = 2.97µg/mL) compared to Amphotericin B (IC50 = 2.40±0.67µg/mL). The novel diterpene erythroivorensin, betulinic acid and the flavanone Eriodictyol, from the ethyl acetate fraction, showed weak activity. UPLC-QTOF-MS/MS was used to identify the cassaine diterpenoids from the active methanol fraction. Here, 10 compounds of this type were putatively identified from the ethanol crude extract. CONCLUSION: The fragmentation mechanism of these metabolites is also proposed and are expected to serve as reference template for identification of these and related compounds in future. The presence of these compounds is an indication that they are an inherited and evolutionary component of plants belonging to the Erythrophleum genus. Our results further present another dimension where these compounds and their relative abundances can be used as chemo-taxonomical bio-markers of the genus. The present study also successfully demonstrated/re-affirmed the use of UPLC-QTOF-MS/MS as a robust technique for the characterization of natural products.

Mosquito larvicidal activity of Cassia tora seed extract and its key anthraquinones aurantio-obtusin and obtusin.

BACKGROUND: The edible and medicinal leguminous plant Cassia tora L. (Fabaceae) is known to possess insecticidal properties against a wide range of plant-feeding insects. However, the bioactivity of extracts of this plant and their constituents against vectors of medical importance has been largely unexplored. We investigated the mosquito larvicidal activity of the seed extract and its major anthraquinones against larvae of the African malaria vector Anopheles gambiae (s.s.). METHODS: Third-fourth instar larval mortality was observed after 24, 48, 72 and 96 h of exposure to varying doses of the extracts, and two anthraquinones isolates identified using liquid chromatography- quadrupole time of flight mass spectrometry (LC-QtoF-MS). The mosquito larval mortality was evaluated relative to the natural insecticide azadirachtin. RESULTS: Fractionation of the crude extract decreased mosquito larvicidal activity, however, larvicidal activity increased with increasing dose of the treatment and exposure time. The known anthraquinones aurantio-obtusin and obtusin were identified as key larvicidal compounds. Aurantio-obtusin and obtusin, exhibited similar toxicity to larvae of A. gambiae (s.s.) with LD50 values of 10 and 10.2 ppm, respectively. However, the two anthraquinones were four- and ~ six-fold less potent than that of the crude seed extract and azadirachtin, which had comparable LD50 values of 2.5 and 1.7 ppm, respectively. CONCLUSION: Both aurantio-obtusin and obtusin showed mosquito larvicidal activity which were comparable to their respective fractions although they were less potent relative to the crude extract and azadirachtin. Further studies need to be conducted on C. tora for its exploitation as a potential eco-friendly tool in mosquito larval source reduction.

Antiplasmodial activity of selected medicinal plants used to treat malaria in Ghana.

The use of medicinal plants for the treatment of diseases including malaria is commonplace in Ghanaian traditional medicine, though the therapeutic claims for most plants remain unvalidated. Antiplasmodial activity of the aqueous extracts and successively obtained petroleum ether, ethyl acetate and methanol fractions of the whole Phyllanthus fraternus plant, the leaves of Tectona grandis, Terminalia ivorensis and Bambusa vulgaris, and roots of Senna siamea were studied against Plasmodium falciparum chloroquine-sensitive 3D7 and chloroquine-resistant W2 strains. The aqueous extracts were assessed against human umbilical vein endothelial cells (HUVECs) for cytotoxicity, and the organic solvent fractions against human O(+) erythrocytes for haemolytic effect. Both extracts and fractions demonstrated antiplasmodial activity to varied extents. The aqueous extract of T. ivorensis was the most active (3D7, IC50 0.64 ± 0.14; and W2, IC50 10.52 ± 3.55 µg/mL), and together with P. fraternus displayed cytotoxicity (CC50 6.25 ± 0.40 and 31.11 ± 3.31 µg/mL, respectively). The aqueous extracts were generally selective for 3D7 strain of P. falciparum (selectivity indexes (SIs) ≥3.48) but only that of S. siamea was selective for the W2 strain (SI > 2.1). The organic solvent fractions also displayed antiplasmodial activity with the methanol fractions of P. fraternus and T. grandis, and the fractions of B. vulgaris showing activity with IC50 below 1 µg/mL against P. falciparum 3D7 strain; some fractions showed haemolytic effect but with low to high selectivity indexes (SI ≥ 4). The results while justifying the traditional use of the plant materials in the treatment of malaria, however, suggest their cautious use.

The heavy metal contents of some selected medicinal plants sampled from different geographical locations.

BACKGROUND: The levels of 5 minerals namely; lead, arsenic, mercury, cadmium, and aluminum were assessed in 10 medicinal plants sampled from 5 different geographical locations to determine the effect of location on the plants' mineral content. MATERIALS AND METHODS: Atomic absorption spectrophotometry (wet digestion) was used for the analyzes, and content of the minerals per sample was expressed as µg/g. The levels of minerals were compared to their limit specification for herbs and daily total intake of these minerals. A two-way analysis of variance, which tends to look at the effect of the location and the medicinal plant itself on the plants mineral content, was used in the statistical analysis. RESULTS: Lead (Pb) was present in all plant species examined, except Ocimum gratissimum. One plant exceeded the maximum safety limit for lead. Cadmium was also detected in some of the medicinal plant species (44%) whilst majority were below the detection limit (0.002) representing 56%. 40% of the plant species exceeded the limit for cadmium. Mercury and arsenic in all the plant species were below the detection limit (0.001). Significant variation existed in mineral content for the various locations (P ≤ 0.05). CONCLUSION: The findings generally suggest the variation in mineral levels for the various locations. Thus, our study has shown that same species of medicinal plants, growing in different environments, accumulates different levels of heavy metals.

Acaricidal effect of an isolate from Hoslundia opposita vahl against Amblyomma variegatum (Acari: Ixodidae).

BACKGROUND: Hoslundia opposita Vahl. (Lamiaceae), a common local shrub in Ghana, is traditionally known not only for its pharmacological benefits but also for its insecticidal properties. Its acaricidal property, however, has not been investigated. OBJECTIVE: To test the acaricidal effects of the crude extract and fractions of H. opposita leaves as well as to isolate and characterize the acaricidal principles. MATERIALS AND METHODS: The crude methanolic extract, pet. ether, ethyl acetate and aqueous fractions of the leaves of H. opposita were tested against the larvae of the cattle tick, Amblyomma variegatum, using the Larval Packet Test. A bioassay-guided isolation was carried out to identify the acaricidal principle obtained from the ethyl acetate fraction. RESULTS: The active principle was characterised as ursolic acid, a triterpene previously isolated from the leaves of the same plant. The extract and fractions were less potent than the control, malathion (LC(50) 1.14 × 10(-4) mg/ml). Among the plant samples however the crude methanolic extract exhibited the highest effect against the larvae (LC(50) 5.74 × 10(-2) mg/ml), followed by the ethyl acetate fraction (LC(50) 8.10 × 10(-2) mg/ml). Ursolic acid, pet. ether and aqueous fractions however showed weak acaricidal effects with LC(50) values of 1.13 mg/ml, 8.96 × 10(-1) mg/ml and 1.44 mg/ml, respectively. CONCLUSION: Ursolic acid was not as potent as the crude methanolic extract and the ethyl acetate fraction from which it was isolated. The overall acaricidal effect of H. opposita may have been due to synergy with other principles having acaricidal properties.

Antibacterial and antioxidant cassane diterpenoids from Caesalpinia benthamiana.

Bioactivity-guided fractionation of the light petroleum extract of Caesalpinia benthamiana (=Mezoneuron benthamianum) root bark has led to the isolation of two cassane diterpenoids, designated as benthaminin 1 and 2. A third compound, a deoxy form of caesaldekarin C (also referred to as methyl vouacapenate) which has previously been isolated from Caesalpinia major, C. bonducella, Vouacapoua americana and V. macropetala, was also isolated, together with beta-sitosterol and stigmastenone. The antibacterial and antioxidant activities of these cassane diterpenoids have been assessed using the microdilution assay method and DPPH spectrophotometric and TBA lipid peroxidation assays. Benthaminin 1 was the more active antibacterial compound with MIC values of 47.8 microM for both Staphylococcus aureus and Micrococcus flavus. Benthaminin 2 was the more active antioxidant compound and showed IC50 values of 42.7 microM and 74.2 microM for the DPPH and TBA assays, respectively. Deoxycaesaldekarin C possessed both antibacterial and antioxidant activities. The presence of methyl ester and methyl functional groups as well as an unsaturated furan ring appears to confer antibacterial activity. On the other hand, the relatively stronger antioxidant activity of benthaminin 2 may be associated with the presence of an exocyclic methylene function.

In vitro evaluation of effects of two Ghanaian plants relevant to wound healing.

Commelina diffusa and Spathodea campanulata are used as wound-healing agents in Ashanti traditional medicine in Ghana. The methanol extracts of Commelina diffusa herb and Spathodea campanulata bark showed some level of antimicrobial activity with C. diffusa exhibiting selective antifungal activity against Trichophyton species. The extracts reduced the peroxidation of bovine brain extract with an IC(50) value of 1.39 mg/mL and 0.24 mg/mL, respectively. In addition the extracts also exhibited significant antioxidant activity by protecting MRC-5 cells from hydrogen peroxide induced oxidant injury at concentrations between 1 microg/mL and 10 microg/mL. The extracts showed no inhibition of NF-kappaB at 100 microg/mL. The antioxidant activities and antimicrobial activities suggest that the use of the plants in wound healing may be based on antioxidant and antiseptic effects of its constituents.