Anti-Oxidant Potential and Antimalarial Effects of Acanthus polystachyus Delile (Acanthaceae) Against Plasmodium berghei: Evidence for in vivo Antimalarial Activity

Phytochemical Composition, Antioxidant, Antimicrobial, Antibiofilm, and Antiquorum Sensing Potential of Methanol Extract and Essential Oil from Acanthus polystachyus Delile (Acanthaceae)

The evolution of microbes in response to conventional antimicrobials leads to antimicrobial resistance (AMR) and multidrug resistance (MDR), and it is a global threat to public health. Natural products are possible solutions to this massive challenge. In this study, the potential of Acanthus polystachyus extracts was investigated for phytochemical composition and biological properties as antimicrobials. Gas chromatography-mass spectra (GC-MS) analysis of methanol extract (ME) and essential oil (EO) detected 79 and 20 compounds, respectively. The major compounds identified in ME and their abundance were β-sitosterol acetate (16.06%), cholest-5-en-3-yl (9Z)-9-octadecenoate (9.54%), 1-dodecanol (7.57%), (S)-(E)-(-)-4-acetoxy-1-phenyl-2-dodecen-1-one (6.03%), neophytadiene (5.7%), (E)-2-nonadecene (3.9%), hexanol-4-D2 (2.92%), and decane (2.4%). Most compounds have known bioactive functions. In EO, the major compounds were stearyl alcohol (25.38%); cis-9-tetradecenoic acid, isobutyl ester (22.95%); butyl 9-tetradecenoate (10.62%); 11,13-dimethyl-12-tetradecen-1-ol acetate (10.14%); ginsenol (3.48%); and diisooctyl phthalate (2.54%). All compounds are known to be bioactive. The antioxidant activity of ME and EO ranged from 48.3 to 84.2% radical scavenging activity (RSA) and 45.6 to 82% RSA, respectively, with dose dependency. The disc diffusion assay for the antimicrobial activity of ME revealed high inhibition against Acenetobacter baumannii (130.2%), Pseudomonas aeruginosa (100.3%), and Staphylococcus aureus (87.7%). The MIC, MBC/MFC, and MBIC values for ME were 0.5-1.0, 2-4, and 0.5-1.0 mg/mL and for EO were 0.31-0.62, 1.25-2.5, and 0.31-0.62 μL/mL, respectively, indicating inhibition potential as well as inhibition of biofilm formation. The tolerance test values indicated bactericidal activity against most strains and bacteriostatic/fungistatic activity against A. baumannii, E. faecalis, and C. albicans. The antiquorum sensing activity of ME achieved by pyocyanin inhibition assay on P. aeruginosa showed a 51.6% inhibition at 500 μg/mL. These results suggest that ME and EO derived from A. polystachyus leaves are potent, valuable, cost-effective antioxidants and antimicrobials. Both extracts may effectively combat pathogenic and resistant microbes.

Medicinal plants used in traditional treatment of malaria in Ethiopia: a review of ethnomedicine, anti-malarial and toxicity studies

Background

Malaria is extremely common in Ethiopia, and it is one of the country's most serious public health and economic problems. Traditional medicines have long been utilized in Ethiopia by people of various ethnic groups. As a result, the goal of this study is to record the use of Ethiopian medicinal herbs that have been used to treat malaria. Also, a critical review of the literature on the therapeutic properties of these and other Ethiopian medicinal plants that have been tested against Plasmodium spp. parasites was conducted with the goal of highlighting neglected studies and fostering further research in this area.

Methods

A comprehensive literature search was performed in Scopus, Web of Science Core Collection, PubMed, Science Direct, Google Scholar, and Scientific Electronic Library Online (SciELO) from August 2021 to October 2021. The study databases included original articles published in peer reviewed journals covering anti-malarial plants, dated until October 2021.

Results

The review looked at 51 plant species (28 families) that have been used to treat malaria in Ethiopia. The most often used ethnobotanical plant species for the treatment of malaria were Allium sativum, Croton macrostachyus, Carica papaya, and Lepidium sativum. Leaves were used more frequently as a therapeutic preparation than other parts. Plant extracts were found to have very good, good, and moderate anti-malarial activity in mice with rodent Plasmodium species. The most active species were Ajuga remota and Capsicum frufescens, which suppressed parasitaemia by 77.34% and 72.65%, respectively, at an oral dose of 100 mg/kg and an LD50 of above 2000 mg/kg. The compound Aloinoside reported from Aloe macrocarpa leave latex was the most potent; it suppressed parasitaemia by 100% at 400 mg/kg oral dose of Plasmodium berghei infected mice, and its LD50 was above 2000 mg/kg. Toxicity was shown to be safe in 84% of the plant extracts.

Conclusion

In Ethiopia, medicinal plants have a significant part in reducing the severity of malaria due to their widespread use. As a result, more studies are needed to identify and develop effective novel drugs that could be employed in broader malaria eradication efforts.

A review of the ethnomedicinal uses, chemistry, and pharmacological properties of the genus Acanthus (Acanthaceae)

ETHNOPHARMACOLOGICAL RELEVANCE

The Acanthus genus belongs to the Acanthaceae family, and its species are distributed in all continents, mainly in tropical and subtropical regions. Several traditional applications are referred to, but few scientific studies validate them. Despite this, studies in animal models corroborate some of its uses in folk medicine, such as anticancer, antidiabetic, anti-inflammatory, and antinociceptive, which encourages the research on plants of this genus.

AIM OF THE REVIEW

To our knowledge, this document is the first comprehensive review study that provides information on the geographic distribution, botanical characteristics, ethnomedicinal uses, phytochemicals, and pharmacological activities of some Acanthus species to understand the correlation between traditional uses, phytochemical, and pharmacological activities, providing perspectives for future studies.

RESULTS

In traditional medicine, Acanthus species are mainly used for diseases of respiratory, nervous and reproductive system, gastrointestinal and urinary tract, and skin illness. The most used species are A. montanus, A. ilicifolius, and A. ebracteatus. Chemical compounds (125) from different chemical classes were isolated and identified in seven species, mainly from A. ilicifolius, about 80, followed by A. ebracteatus and A. montanus, appearing with a slightly lower number with fewer phytochemical profile studies. Isolated phytoconstituents have been mainly alkaloids, phenylpropanoid glycosides, and phenylethanoids. In addition, aliphatic glycosides, flavonoids, lignan glycosides, megastigmane derivatives, triterpenoids, steroids, fatty acids, alcohols, hydroxybenzoic acids, simple phenols were also cited. Scientific studies from Acanthus species extracts and their phytoconstituents support their ethnomedical uses. Antimicrobial activity that is the most studied, followed by the antioxidant, anti-inflammatory, and anticancer properties, underlie many Acanthus species activities. A. dioscoridis, A. ebracteatus, A. hirsutus, A. ilicifolius, A. mollis, A. montanus, and A. polystachyus have studies on these activities, A. ilicifolius being the one with the most publications. Most studies were essentially performed in vitro. However, the anticancer, antidiabetic, anti-inflammatory and antinociceptive properties have been studied in vivo.

CONCLUSION

Acanthus species have remarkable phytoconstituents with different biological activities, such as antioxidant, antimicrobial, anti-inflammatory, antinociceptive, hepatoprotective, and leishmanicidal, supporting traditional uses of some species. However, many others remain unexplored. Future studies should focus on these species, especially pharmacological properties, toxicity, and action mechanisms. This review provides a comprehensive report on Acanthus genus plants, evidencing their therapeutic potential and prospects for discovering new safe and effective drugs from Acanthus species.

Studies on Activities and Chemical Characterization of Medicinal Plants in Search for New Antimalarials: A Ten Year Review on Ethnopharmacology

Malaria is an endemic disease that affected 229 million people and caused 409 thousand deaths, in 2019. Disease control is based on early diagnosis and specific treatment with antimalarial drugs since no effective vaccines are commercially available to prevent the disease. Drug chemotherapy has a strong historical link to the use of traditional plant infusions and other natural products in various cultures. The research based on such knowledge has yielded two drugs in medicine: the alkaloid quinine from Cinchona species, native in the Amazon highland rain forest in South America, and artemisinin from Artemisia annua, a species from the millenary Chinese medicine. The artemisinin-based combination therapies (ACTs), proven to be highly effective against malaria parasites, and considered as “the last bullet to fight drug-resistant malaria parasites,” have limited use now due to the emergence of multidrug resistance. In addition, the limited number of therapeutic options makes urgent the development of new antimalarial drugs. This review focuses on the antimalarial activities of 90 plant species obtained from a search using Pubmed database with keywords “antimalarials,” “plants” and “natural products.” We selected only papers published in the last 10 years (2011–2020), with a further analysis of those which were tested experimentally in malaria infected mice. Most plant species studied were from the African continent, followed by Asia and South America; their antimalarial activities were evaluated against asexual blood parasites, and only one species was evaluated for transmission blocking activity. Only a few compounds isolated from these plants were active and had their mechanisms of action delineated, thereby limiting the contribution of these medicinal plants as sources of novel antimalarial pharmacophores, which are highly necessary for the development of effective drugs. Nevertheless, the search for bioactive compounds remains as a promising strategy for the development of new antimalarials and the validation of traditional treatments against malaria. One species native in South America, Ampelozyzyphus amazonicus, and is largely used against human malaria in Brazil has a prophylactic effect, interfering with the viability of sporozoites in in vitro and in vivo experiments.