Antimicrobial investigation of ethnobotanically selected guinean plant species

The genus Landolphia P.Beauv. (Apocynaceae): A comprehensive review on its ethnobotanical utilizations, pharmacology and nutritional potential

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Landolphia is an important resource for African traditional medicine. Among the 60 different accepted species, nearly every plant part of the genus (bark, fruit, latex, leaf, leaf sap, root, rootbark, twig) from 13 species is utilized by traditional healers around Africa. Accordingly, many pharmacological studies (42) were performed on the most common species (11).

AIM OF THE STUDY

This comprehensive literature review summarizes all publications dealing on one of the 60 plant species from the genus Landolphia. An overview about already performed analysis is given and important aspects and knowledge gaps are highlighted for the direction of future research activities.

MATERIALS AND METHODS

A systematic web search taking into account the major platforms Web of Science, Scopus, PubMed, SciFinder and Google Scholar was performed for the term Landolphia. All relevant datasets, published between 1804 and 2022, were ordered according to their topics in different sections and compared to each other. A network visualization of the keywords via VOS Viewer was additionally performed.

RESULTS

In total, 209 publications were retrieved from the search engines, mainly written in English. Predominant are ethnopharmacological studies, which identified 292 phytochemicals in plant parts of the whole genus. Diverse biological activities were detected in different plant extracts, and five species were determined as of special interest for the treatment of malaria. Further research topics identified are botanical aspects, ethnobotanical utilizations, ecological aspects, the potential as source for human and animal nutrition, the manufacturing of rubber, economic aspects, biomechanical studies and others. L. owariensis is the most studied plant as it is abundant in continental Africa.

CONCLUSIONS

This review serves as a database for upcoming research on the genus Landolphia and directs existing knowledge gaps. A wide range of chemical components are already identified, but their exact content in the respective plant parts and their biological activity remains mainly unknown. Utilization patterns from traditional medicine are only partially analyzed as demonstrated for the applications as aphrodisiac, to treat skin diseases or as antidiabetic. Nutritional analyses likewise focus on several species of Landolphia and lack for the wide range of known edible fruits. The demand for new natural products in terms of medicine, rubber and nutrition is still high and the genus Landolphia seems to be a promising resource covering many aspects at once.

The relevance of quantitative ethnobotanical indices for ethnopharmacology and ethnobotany

ETHNOPHARMACOLOGICAL RELEVANCE

As an interdisciplinary field of research ethnopharmacology draws on methodologies and methods from a variety of disciplines. A range of ethnobotanical indices are frequently used to transform primary data obtained through field studies into statistical measures. These indices are claimed to serve as a proxy for efficacy or drug discovery (Fidelity Level 'FL') and to show the importance of botanical drugs and plants used as medicines (Relative Importance 'RI', Use Value 'UV' or Cultural Importance Index 'CI', Cultural Value Index 'CV', Relative Frequency of Citation 'RFC'). This is, however, doubtful, as these indices have not been developed by statisticians, nor by pharmacologists while a proof of concept is lacking. Moreover, the question whether a simple number can summarize the cultural value or importance of plants is not only mathematical but also epistemological.

MATERIAL AND METHODS

The FL, RI, UV/CI, CV and the RFC are shortly reviewed. Their statistical rigour is explained and the relevance for ethnobotany, ethnopharmacology and drug discovery discussed.

RESULTS

The effect of the sample size on the dispersal of data and the differential probability of botanical drugs being used for the different categories of use are not being considered by these indices. They lack statistical rigour and are simple percentage calculations. Moreover, important factors influencing plant use, such as the availability of pharmaceutical drugs, or the severity of diseases covered by the use-categories, are not accounted for.

CONCLUSION

Especially unexperienced and young researchers may be ensnared by using ethnobotanical indices to describe their field data. However, the cultural value and importance of plants in general, and more specifically, of medicinal plants and botanical drugs cannot be summed up by numbers. The discussed indices encrypt parts of the primary data but fail to show the value or importance of plant use because the reasons for which plants are valued or important to people are far more complex than what the formulations of these indices suggest. The indices also lack the power to pinpoint plant species or botanical drugs for drug discovery that contextualized primary data has. Botanical drugs may be useful for a range of disorders or only for specific indications, according to their pharmacologic properties. Therefore, the exclusiveness of therapeutical applications (FL) does not serve as a proxy for effectiveness. The solution is to use and understand the contextualized primary data.

Design, synthesis, biological screening and molecular docking studies of novel multifunctional 1,4-di (aryl/heteroaryl) substituted piperazine derivatives as potential antitubercular and antimicrobial agents

In this paper, two series of novel multifunctional 1, 4-di (aryl/heteroaryl) substituted piperazine derivatives (6a-d & 7a-d) were synthesized, characterized, and evaluated for their antitubercular, antibacterial, and antifungal activities. A step-wise reduction, bromination and substitution reactions on various aldehydes resulted in alcohols (2a-d), bromides (3a-d), and titled novel compounds (6a-d & 7a-d) in moderate to good yields (48-85%). The novel compounds were evaluated for their antitubercular and antimicrobial activities. Compound 7a exhibited promising antitubercular activity (MIC: 0.65 µg/mL) almost equal to the Rifampicin, while the rest of the compounds were moderately active against MTB H37Rv except 6b. Compounds 7a and 6b showed good activity against tested fungal pathogens. Compounds 7a and 7b were proven as the best bacterial agents. Molecular docking studies were in agreement with the in-vitro results. Docking analyses show that all the synthesized molecules bind to the target protein Mtb RNAP (PDB ID: 5UHC) fairly strongly. All the compounds were evaluated for their in vitro cytotoxicity effect using the MTT assay method against human cancer cell line MCF-7. The compounds demonstrated growth inhibitory effect on the cell line with significant IC₅₀ values ranging between 8.20 and 34.45 µM. Most importantly, compound 7a displayed good binding affinity towards the tested protein with binding energy -7.30 kcal/mol and a stronger hydrogen bond distance of 2.2 Å with ASN-493 residue. Thus, the present research highlighted the potential role of novel piperazine derivatives as potential antitubercular, and antimicrobial candidates and further good research into optimization might result in the development of new antitubercular drug candidates.

Malaria in Guinean Rural Areas: Prevalence, Management, and Ethnotherapeutic Investigations in Dionfo, Sub-Prefecture of Labe

As part of a validation program of antimalarial traditional recipes, an ethnotherapeutic approach was applied in Dionfo, a meso-endemic Guinean rural area where conventional health facilities are insufficient. A prevalence investigation indicated a malarial burden of 4.26%. Ethnomedical and ethnobotanical surveys led to a collection of 63 plant species used against malaria from which Terminalia albida (Combretaceae) was one of the most cited. Ethnotherapeutic evaluation of a remedy based on T. albida was applied to 9 voluntary patients suffering from uncomplicated malaria. Treatment of 7 to 14 days led to an improvement of clinical symptoms and a complete parasite clearance achievement of 8/9 patients without side effects. In addition to antiplasmodial activity in vitro and in vivo previously described, this study indicates an efficacy to support the antimalarial traditional use of T. albida, which could constitute a first-aid treatment when access to other medicines is delayed in the Dionfo community. Ethnotherapeutical investigation could be a valuable approach to guide subsequent investigations on traditional remedies.

Phytochemical Investigation, Antimicrobial, Antioxidant and Anticancer Activities of Acer cappadocicum Gled

The appearance of novel microbial resistance, diverse cancer ailment and several other morbidities such as appetite loss, hair loss, anemia, cell damage, etc., are among most critical situation that keeps the phytochemical quest on. Thus, this study characterized the antimicrobial, antioxidant, and anticancer potentials of a rarely accessed Acer cappadocicum gled (AC) population thriving in a remote Palas Valley in northern Pakistan. Leaf extracts of the plant were prepared in organic solvents with different polarities through maceration. Extracts were subjected to antimicrobial, antioxidant, and anticancer activities using agar well, DPPH and cell viability assays. A. cappadocicum methanolic extract (ACM) significantly inhibited bacterial growth, followed by n-butanolic extract (ACB) with the second-highest bacterial inhibition. Similar activity was observed against mycelial growth inhibition in plant-fungal pathogen by ACM and ACB. However, human pathogenic fungi did not affect much by extracts. In antioxidant assessment, the chloroform extract (ACC) showed strong scavenging activity and in cytotoxic evaluation, extracts restricted growth proliferation in cancer cells. The inhibitory evidence of extracts, potent scavenging ability, and low cell viability of human-derived cell lines supports the antimicrobial, antioxidant and anticancerous potential of A. cappadocicum. It advances our quest for natural product research.

Antiplasmodial Oleanane Triterpenoids from Terminalia albida Root Bark

Phytochemical investigation of the n-BuOH extract of the roots of Terminalia albida Sc. Elliot (Combretaceae) led to the isolation and identification of 10 oleanane triterpenoids (1-10), among which six new compounds, i.e., albidanoside A (2), albidic acid A (4), albidinolic acid (5), albidienic acid (8), albidolic acid (9), and albidiolic acid (10), and two triterpenoid aglycones, i.e., albidic acid B (6) and albidic acid C (7), were isolated here for the first time from a natural source, along with two known compounds. The structures of these constituents were established by means of 1D and 2D NMR spectroscopy and ESI mass spectrometry. The isolated compounds were evaluated for their antiplasmodial and antimicrobial activity against the chloroquine-resistant strain Plasmodium falciparum K1, Candida albicans, and Staphylococcus aureus. Compounds 1-4, 6, 7, and 8 showed moderate antiplasmodial activity with IC₅₀ values between 5 and 15 μM. None of the tested compounds were active against C. albicans or S. aureus. These findings emphasize the potential of T. albida as a source for discovery of new antiplasmodial compounds.

Bioassay-guided isolation of antiplasmodial and antimicrobial constituents from the roots of Terminalia albida

ETHNOPHARMACOLOGICAL RELEVANCE

Terminalia albida (Combretaceae), widely used in Guinean traditional medicine, showed promising activity against Plasmodium falciparum and Candida albicans in previous studies. Bioassay-guided fractionation was carried out in order to isolate the compounds responsible for these activities.

MATERIALS AND METHODS

Fractionation and isolation were performed by flash chromatography, followed by semi-preparative HPLC-DAD-MS. The structural elucidation of the isolated compounds was carried out by 1D and 2D NMR as well as HR-ESI-MS. Isolated compounds were evaluated against Plasmodium falciparum, Candida albicans, Staphylococcus aureus and Escherichia coli, and their cytotoxicity against MRC-5 cells was determined.

RESULTS

Bioassay-guided fractionation of Terminalia albida root resulted in the isolation of 14 compounds (1-14), and their antimicrobial properties were evaluated. Pantolactone (1) (IC₅₀ 0.60 ± 0.03 μM) demonstrated significant activity against P. falciparum. Other compounds, including 3,4,3'-tri-O-methyl-ellagic acid (3), the triterpenes arjunolic acid (5), arjungenin (6), arjunic acid (7) and arjunglucoside II (10), and the phenol glycoside calophymembranside-B (14), were less active and showed IC₅₀ values in the range 5-15 μM. None of the tested compound showed antibacterial or antifungal activity.

CONCLUSION

These results may explain at least in part the activity of the root extract of T. albida against P. falciparum.