The genus Warburgia: a review of its traditional uses and pharmacology

Unveiling Drimenol: A Phytochemical with Multifaceted Bioactivities

Drimenol, a phytochemical with a distinct odor is found in edible aromatic plants, such as Polygonum minus (known as kesum in Malaysia) and Drimys winteri. Recently, drimenol has received increasing attention owing to its diverse biological activities. This review offers the first extensive overview of drimenol, covering its sources, bioactivities, and derivatives. Notably, drimenol possesses a wide spectrum of biological activities, including antifungal, antibacterial, anti-insect, antiparasitic, cytotoxic, anticancer, and antioxidant effects. Moreover, some mechanisms of its activities, such as its antifungal effects against human mycoses and anticancer activities, have been investigated. However, there are still several crucial issues in the research on drimenol, such as the lack of experimental understanding of its pharmacokinetics, bioavailability, and toxicity. By synthesizing current research findings, this review aims to present a holistic understanding of drimenol, paving the way for future studies and its potential utilization in diverse fields.

Inhibition of pro-inflammatory cytokines by selected southern African medicinal plants in LPS-stimulated RAW 264.7 macrophages

ETHNOPHARMACOLOGICAL RELEVANCE

Bark is frequently used in southern African traditional medicine to treat inflammation, yet it remains to be rigorously examined for its immunological and anti-inflammatory activity.

AIM OF THE STUDY

Barks obtained from ten important and popular southern Africa plants were evaluated for their anti-inflammatory and immunomodulatory properties against the secretion of some pro-inflammatory cytokines (interleukin (IL)-1β, IL-6, tumour necrosis factor-α (TNF-α), and interferon-gamma (IFN-γ) as well as chemokines (monocyte chemoattractant protein 1 (MCP-1) and macrophage inflammatory protein (MIP)-2) in murine RAW 264.7 macrophages.

MATERIALS AND METHODS

The inhibitory effects of aqueous and ethanol extracts were determined using cytokine multiplex-bead assays in lipopolysaccharide (LPS)-stimulated and unstimulated RAW 264.7 cells.

RESULTS

Overall, the ethanol extracts were more potent cytokine inhibitors compared to the aqueous extracts. The LPS-stimulated cells treated with the ethanol extracts of Erythrina lysistemon Hutch., Pterocelastrus rostratus Walp. Syzygium cordatum Hochst. ex Krauss and Warburgia salutaris (G. Bertol.) Chiov., demonstrated significant (p < 0.005) inhibition up to 85% of IL-1β, IL-6, and TNF-α secretion compared to the LPS control. Additionally, P. rostratus and S. cordatum aqueous bark extracts substantially decreased the secretion of all the tested cytokines and chemokines. Chemical investigation of the S. cordatum extract resulted in the identification of four ellagic acid derivatives: ellagic acid 4-O-α-rhamnopyranoside (1), ellagic acid 4-O-α-4″-acetylrhamnopyranoside (2), 3-O-methylellagic acid 4'-O-α-3″-O-acetylrhamnopyranoside (3) and 3-O-methylellagic acid 4'-O-α-4″-O-acetylrhamnopyranoside (4), along with mixtures of ellagic acid 4-O-α-2″-acetylrhamnopyranoside (5), ellagic acid 4-O-α-3″-acetylrhamnopyranoside (6) and ellagic acid (7). Their structures were confirmed by mass spectrometry, NMR spectroscopy, and comparison with data from literature.

CONCLUSION

The cytokine inhibition properties of most of the medicinal plants screened herein are reported for the first time. Our results provide insights into the mechanism of action by which the selected southern African medicinal plants regulate inflammation.

Regulatory activities of Warbugia ugandensis ethanolic extracts on colorectal cancer-specific genome expression dose-dependently

The evaluation of natural biomass sources is a promising strategy in accelerating the development of novel anti-cancer medications. Our study aimed to evaluate the activity of W. ugandensis ethanolic roots and stems extracts on the expression of five targeted genes (COX-2, CASPS-9, Bcl-xL, Bcl2 and 5-LOX) in colorectal cancer (CRC) cell lines (Caco-2). Plant extracts were obtained using serial exhaustive extraction and dissolved in Dimethyl sulfoxide appropriately for bioassay. Caco-2 cell lines were passaged, treated with plant extracts at varying concentrations and their RNA's isolated for evaluation. Our unique study reports on W. ugandensis as efficient natural inhibitors of CRC growth, by directly linking its phytoconstituents to; downregulation of COX-2, 5-LOX, Bcl-xL, Bcl2 and upregulation of CASPS9 genes dose-dependently. We present W. ugandensis ethanolic roots and stems extracts as promising natural inhibitors for CRC carcinogenesis and recommend in vivo and subsequent clinical trials, with substantial clinical effects postulated. We further suggest studies on identification and characterization of the specific metabolites in W. ugandensis involved in the modulatory mechanisms, resulting to inhibition of CRC growth and possible metastases.

Medicinal Uses of the Fabaceae Family in Zimbabwe: A Review

The current study is aimed at providing a systematic review of the ethnomedicinal, phytochemical and pharmacological properties of Fabaceae species used as sources of traditional medicinies in Zimbabwe. Fabaceae is one of the well-known plant families of ethnopharmacological importance. Of the approximately 665 species of the Fabaceae family occurring in Zimbabwe, about 101 are used for medicinal purposes. Many communities in the country, mainly in peri-urban, rural and marginalized areas with limited access to healthcare facilities, rely on traditional medicines as their primary healthcare. The study reviewed research studies undertaken on Zimbabwe's Fabaceae species during 1959 to 2022. Information was gathered from literature sourced from Google Scholar, Science Direct, Scopus, PubMed, books, dissertations, theses and scientific reports. This study showed that 101 species are traditionally used to manage human and animal diseases in Zimbabwe. The genera with the highest number of medicinal uses are Indigofera, Senna, Albizia, Rhynchosia and Vachellia. Species of these genera are used as traditional medicines against 134 medical conditions, mainly gastrointestinal conditions, female reproductive conditions, respiratory conditions and sexually transmitted infections. Shrubs (39.0%), trees (37.0%) and herbs (18.0%) are the primary sources of traditional medicines, while roots (80.2%), leaves (36.6%), bark (27.7%) and fruits (8.9%) are the most widely used plant parts. Many of Zimbabwe's Fabaceae species used as sources of traditional medicines have been assessed for their phytochemical and pharmacological properties, corroborating their medicinal uses. However, there is a need to unravel the therapeutic potential of the family through further ethnopharmacological research focusing on toxicological studies, in vitro and in vivo models, biochemical assays and pharmacokinetic studies.

New Terpenoids from the Corticioid Fungus Punctularia atropurpurascens and their Antimycobacterial Evaluation

Chemical investigation of Punctularia atropurpurascens strain HM1 (Punctulariaceae), a corticioid isolated from a decorticated piece of Quercus bark collected in Bosque de Tlalpan, Mexico City, led to the isolation of a new drimane, 1-α-hydroxy-isodrimenine (1: ) and a new tetrahydroxy kauranol, 16-hydroxy-phlebia-nor-kauranol (2: ), together with the known N-phenylacetamide (3: ). Structures of all compounds were elucidated by spectroscopic and spectrometric methods, and the absolute configuration of 1: and 2: was confirmed via single-crystal X-ray crystallography. The isolated compounds showed modest antimycobacterial activity.

Safety and Efficacy of Medicinal Plants Used to Manufacture Herbal Products with Regulatory Approval in Uganda: A Cross-Sectional Study

Introduction

The Uganda National Drug Authority requires phytochemical screening, freedom from microbial contamination, and evidence of safety and efficacy of the constituent plants to register herbal products. Since Uganda has no pharmacopeia, safety, efficacy, and plant processing information are not readily available. We documented the plant materials used to manufacture products in Uganda and established evidence of their safety and efficacy and availability of monographs.

Methods

The NDA register of herbal products was reviewed, and a product list was extracted. The herbal products were purchased from local pharmacies, and their labels were studied to identify plant ingredients and drug use. Literature was reviewed to document evidence of the safety and efficacy of the plant materials concerning manufacturer's claims. Also, the WHO and available African Pharmacopeia were searched to establish the availability of the plant monographs.

Results

Of the 84 NDA-registered local products, only 18 were obtained from the market; 82% were indicated for respiratory tract disorders. Thirty-three plant materials were listed with Eucalyptus globulus Labill, being the commonest. Several in vitro and in vivo studies demonstrate efficacy, thus supporting the use of the selected plant species for empirical treatment as stated on the product label. While most plants were safe, some species such as Albizia coriaria Oliv. had dose-dependent toxicities that cannot be predicted in combinations. The WHO, African Pharmacopoeia, and West African Herbal Pharmacopoeia had only 16 plant monographs of the 33 plants of interest. Nevertheless, Aloe vera (L.) Burm.f., Azadirachta indica A.Juss., Zingiber officinale Roscoe, and Allium sativum L. monographs were published by all three pharmacopoeias.

Conclusions

Preclinical evidence of safety and efficacy exists in the literature for most of the plants used to manufacture registered herbal products in Uganda. More specific bioassays and clinical trials are required for the products to provide conclusive evidence of safety and toxicity. Monographs are urgently needed for the Ugandan plants.

Anticancer Activity of Natural and Semi-Synthetic Drimane and Coloratane Sesquiterpenoids

Drimane and coloratane sesquiterpenoids are present in several plants, microorganisms, and marine life. Because of their cytotoxic activity, these sesquiterpenoids have received increasing attention as a source for new anticancer drugs and pharmacophores. Natural drimanes and coloratanes, as well as their semi-synthetic derivatives, showed promising results against cancer cell lines with in vitro activities in the low micro- and nanomolar range. Despite their high potential as novel anticancer agents, the mode of action and structure–activity relationships of drimanes and coloratanes have not been completely enlightened nor systematically reviewed. Our review aims to give an overview of known structures and derivatizations of this class of sesquiterpenoids, as well as their activity against cancer cells and potential modes-of-action. The cytotoxic activities of about 40 natural and 25 semi-synthetic drimanes and coloratanes are discussed. In addition to that, we give a summary about the clinical significance of drimane and coloratane sesquiterpenoids.

Stimulation of ROS Generation by Extract of Warburgia ugandensis Leading to G0/G1 Cell Cycle Arrest and Antiproliferation in A549 Cells

Warburgia ugandensis Sprague (WU) is a traditional medicinal plant used for the treatment of various diseases, including cancer, in Africa. This study aimed to evaluate the anti-non-small cell lung cancer (NSCLC) activities of WU against A549 cells and to reveal potential molecular mechanisms. The cytotoxicity of various WU extracts was evaluated with HeLa (cervical cancer), HepG2 (liver cancer), HT-29 (colorectal cancer), and A549 (non-small cell lung cancer) cells by means of Sulforhodamine B (SRB) assay. Therein, the dimethyl carbonate extract of WU (WUD) was tested with the most potent anti-proliferative activity against the four cancer cell lines, and its effects on cell viability, cell cycle progression, DNA damage, intracellular reactive oxygen species (ROS), and expression levels of G₀/G₁-related proteins in A549 cells were further examined. First, it was found that WUD inhibited the proliferation of A549 cells in a time- and dose-dependent manner. In addition, WUD induced G₀/G₁ phase arrest and modulated the expression of G₀/G₁ phase-associated proteins Cyclin D1, Cyclin E1, and P27 in A549 cells. Furthermore, WUD increased the protein abundance of P27 by inhibiting FOXO3A/SKP2 axis-mediated protein degradation and also significantly induced the γH2AX expression and intracellular ROS generation of A549 cells. It was also found that the inhibitory effect of WUD on the proliferation and G₀/G₁ cell cycle progression of A549 cells could be attenuated by NAC, a ROS scavenger. On the other hand, phytochemical analysis of WUD with UPLC-QTOF-MS/MS indicated 10 sesquiterpenoid compounds. In conclusion, WUD exhibited remarkable anti-proliferative effects on A549 cells by improving the intracellular ROS level and by subsequently modulating the cell proliferation and G₀/G₁ cell cycle progression of A549 cells. These findings proved the good therapeutic potential of WU for the treatment of NSCLC.

Identification of Anti-Inflammatory and Anti-Proliferative Neolignanamides from Warburgia ugandensis Employing Multi-Target Affinity Ultrafiltration and LC-MS

Previous reports have illustrated that the incidence and mortality of cancer are increasing year by year worldwide. In addition, the occurrence, development, recurrence and metastasis of cancer are closely related to inflammation, which is a kind of defensive response of human body to various stimuli. As an important medicinal plant in Africa, Warburgia ugandensis has been reported to have certain anti-inflammatory and anti-proliferative activities, but its specific components and mechanisms of action remain elusive. To tackle this challenge, affinity ultrafiltration with drug targets of interest coupled to high-performance liquid chromatography-mass spectrometry (AUF-HPLC-MS/MS) could be utilized to quickly screen out bioactive constituents as ligands against target enzymes from complex extracts of this plant. AUF-HPLC-MS/MS with four drug targets, i.e., cyclooxygenase-2 (COX-2), 5-lipoxygenase (5-LOX), topoisomerase I (Top I) and topoisomerase II (Top II) were used to rapidly screen and characterize the anti-inflammatory and anti-proliferative natural ligands from W. ugandensis, and the resulting potential active compounds as ligands with specific binding affinity to COX-2, 5-LOX, Top I and Top II, were isolated with modern separation and purification techniques and identified with spectroscopic method like NMR, and then their antiinflammatory and anti-proliferative activities were tested to verify the screening results from AUF-HPLC-MS/MS. Compounds 1 and 2, which screened out and identified from W. ugandensis showed remarkable binding affinity to COX-2, 5-LOX, Top I and Top II with AUF-HPLC-MS/MS. In addition, 1 new compound (compound 3), together with 5 known compounds were also isolated and identified from W. ugandensis. The structure of compound 3 was elucidated by extensive 1D, 2D NMR data and UPLC-QTOF-MS/MS. Furthermore, compounds 1 and 2 were further proved to possess both anti-inflammatory and anti-proliferative activities which are in good agreement with the screening results using AUF-HPLC-MS/MS. This work showcased an efficient method for quickly screening out bioactive components with anti-inflammatory and anti-proliferative activity from complex medicinal plant extracts using AUF-HPLC-MS/MS with target enzymes of interest, and also demonstrated that neolignanamides (compounds 1 and 2) from W. ugandensis would be the active components responsible for its anti-inflammatory and anti-proliferative activity with the potential to treat cancer and inflammation.

New Lignanamides with Antioxidant and Anti-Inflammatory Activities Screened Out and Identified from Warburgia ugandensis Combining Affinity Ultrafiltration LC-MS with SOD and XOD Enzymes

Warburgia ugandensis, also known as "green heart," is widely used for the treatment of various diseases as a traditional ethnomedicinal plant in local communities in Africa. In this work, 9 and 12 potential superoxide dismutase (SOD) and xanthine oxidase (XOD) ligands from W. ugandensis were quickly screened out by combining SOD and XOD affinity ultrafiltration with LC-MS, respectively. In this way, four new lignanamides (compounds 11-14) and one new macrocyclic glycoside (compound 5), along with three known compounds (compounds 1, 3, and 7), were isolated and identified firstly in this species. The structures of the new compounds were elucidated by spectroscopic analysis, including NMR and UPLC-QTOF-MS/MS. Among these compounds, compound 14 showed the highest 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azinobis-(3-ethylbenzthiazoline)-6-sulfonic acid (ABTS) radical scavenging activities, and total ferric-reducing antioxidant power (FRAP) with IC50 values of 6.405 ± 0.362 µM, 5.381 ± 0.092 µM, and 17.488 ± 1.625 mmol TE/g, respectively. Moreover, compound 14 displayed the highest inhibitory activity on cyclooxygenase-2 (COX-2) with IC50 value of 0.123 ± 0.004 µM, and the ranking order of other compounds' IC50 values was 13 > 11 > 7 > 1 > 12. The present study suggested that lignanamides might represent interesting new characteristic functional components of W. ugandensis to exert remarkable antioxidant and anti-inflammatory activities. Moreover, compound 14, a new arylnaphthalene lignanamide, would be a highly potential natural antioxidant and anti-inflammatory agent from W. ugandensis.

A Bibliographic Assessment Using the Degrees of Publication Method: Medicinal Plants from the Rural Greater Mpigi Region (Uganda)

In ethnopharmacological research, many field assessment tools exist. Yet, these miss that critical point of how to really determine which species merit the costly lab studies, e.g., evaluation of traditional use via pharmacological assays and isolation of bioactive secondary metabolites. This gap can be filled with the introduction of a new tool for literature assessment: the Degrees of Publication (DoPs). In this study, its application is illustrated through an extensive bibliographic assessment of 16 medicinal plant species that were recently identified in the Greater Mpigi region of Uganda as being frequently used by local traditional healers in the treatment of medical disorders (namely, Albizia coriaria, Cassine buchananii, Combretum molle, Erythrina abyssinica, Ficus saussureana, Harungana madagascariensis, Leucas calostachys, Microgramma lycopodioides, Morella kandtiana, Plectranthus hadiensis, Securidaca longipedunculata, Sesamum calycinum subsp. angustifolium, Solanum aculeastrum, Toddalia asiatica, Warburgia ugandensis, and Zanthoxylum chalybeum). These species are suspected to be understudied, and a thorough bibliographic assessment has not been previously performed. Thus, the objectives of our study were to undertake a comparative assessment of the degree to which each of these plant species has been studied in the past, including evaluation of the quality of the journals where results were published in. The determination of the DoPs enabled successful assessment of the degrees to which each individual plant species has been studied so far, while also taking into account the methodological “research chain of ethnopharmacology” from ethnobotanical studies (“traditional use”) to pharmacological assays (“bioactivity”) and finally to pharmacognostic research (“structure elucidation”). The significance of a research paper was assessed by determining whether its journal and publishing house were members of the Committee on Publication Ethics (COPE). In total, 634 peer-reviewed publications were reviewed covering the period of 1960–2019, 53.3% of which were published in journals and by publishing houses affiliated with COPE (338 publications). The literature assessment resulted in the identification of understudied plants among the selected species. The majority of plants reviewed have not been sufficiently studied; six species were classified as being highly understudied and three more as being understudied: C. buchananii, F. saussureana, L. calostachys, M. lycopodioides, M. kandtiana, and S. calycinum subsp. angustifolium and A. coriaria, P. hadiensis, and S. aculeastrum, respectively. The newly introduced DoPs are a useful tool for the selection of traditionally used species for future laboratory studies, especially for pharmacological bioassays, isolation procedures, and drug discovery strategies.

Essential Oil Variation within Warburgia salutaris-A Coveted Ethnomedicinal Aromatic Tree

Warburgia salutaris, known as 'Pepper bark', is an ethnomedicinally important tree found in the southern regions of Africa. A total of 75 fresh leaf specimens of W. salutaris (n=40 wild and 35 cultivated) were collected from the Limpopo (wild) and KwaZulu-Natal provinces (cultivated), two distinct locations in South Africa. In this study, the leaf essential oils obtained by hydrodistillation were characterized using gas chromatography coupled to mass spectrometry/flame ionization detection (GC/MS/FID). More than 15 compounds, accounting for 90-99 % of the total oil composition were identified. The analysis revealed that myrcene (0.6-65.3 %), (E)-β-ocimene (nd-56.9 %), (Z)-β-ocimene (nd-19.1 %), α-pinene (nd-19.1 %) and limonene (nd-11.7 %) are major constituents of W. salutaris essential oils. Chemometric analysis revealed two major chemotypes within the essential oils with a modeled variation of approximately 60 %. Linalool and germacrene D were revealed as markers associated with the wild-harvested oils, while cultivated oils were distinguished by higher levels of limonene and α-humulene. The intra-population variation indicated two chemically distinct chemotypes from three different populations, however, the season of harvest did not have a direct influence on the chemical profiles of the essential oils.

Biofilm inhibiting properties of compounds from the leaves of Warburgia ugandensis Sprague subsp ugandensis against Candida and staphylococcal biofilms

ETHNOPHARMACOLOGICAL RELEVANCE

Warburgia ugandensis Sprague subspecies ugandensis is a plant widely distributed in Eastern, Central and Southern Africa. In humans, it is used to treat respiratory infections, tooth aches, malaria, skin infections, venereal diseases, diarrhea, fevers and aches.

AIM OF THE STUDY

This study aims to identify the bioactive compounds against clinically important biofilm-forming strains of Candida and staphylococci that are responsible for tissue and implanted device-related infections.

METHODS

Using a bioassay-guided fractionation approach, hexane -, ethanol -, acetone - and water extracts from the leaves of W. ugandensis, their subsequent fractions and isolated compounds were tested against both developing and preformed 24 h-biofilms of Candida albicans SC5314, Candida glabrata BG2, Candida glabrata ATCC 2001, Staphylococcus epidermidis 1457 and Staphylococcus aureus USA 300 using microtiter susceptibility tests. Planktonic cells were also tested in parallel for comparison purposes. Confocal scanning laser microscopy was also used to visualize effects of isolated compounds on biofilm formation.

RESULTS

Warburganal, polygodial and alpha-linolenic acid (ALA) were the major bioactive compounds isolated from the acetone extract of W. ugandensis. For both warburganal and polygodial, the biofilm inhibitory concentration that inhibits 50% of C. albicans developing biofilms (BIC₅₀) was 4.5 ± 1 and 10.8 ± 5 μg/mL respectively. Against S. aureus developing biofilms, this value was 37.9 ± 8 μg/mL and 25 μg/mL with warburganal and ALA respectively. Eradication of preformed 24 h biofilms was also observed. Interestingly, synergy between the sesquiterpenoids and azoles against developing C. albicans biofilms resulted in an approximately ten-fold decrease of the effective concentration required to completely inhibit growth of the biofilms by individual compounds. The hydroxyl group in position C-9 in warburganal was identified as essential for activity against staphylococcal biofilms. We also identified additional promising bioactive sesquiterpenoids; drimenol and drimendiol from the structure-activity relationship (SAR) studies.

CONCLUSIONS

ALA and four sesquiterpenoids: polygodial, warburganal, drimenol and drimendiol, have shown biofilm-inhibitory activity that has not been reported before and is worth following up. These compounds are potential drug candidates to manage biofilm-based infections, possibly in combination with azoles.

Ethnopharmacological Potentials of Warburgia ugandensis on Antimicrobial Activities

Warburgia ugandensis (W. ugandensis) is known by various names, including the East African greenheart, pepper bark tree, and Ugandan greenheart, and has a rich history of extensive use in the treatment of a host of human diseases in many African countries. This review is based on the botany and ethnopharmacological potentials of W. ugandensis for the treatment of pneumonia, asthma, malaria, candidiasis, skin infections, human immunodeficiency virus opportunistic infections, diarrhea, and measles given the common use in the management of these diseases. Extracts from W. ugandensis have strong antimicrobial activities against a broad spectrum of pathogens mainly because of the presence of abundant terpenoids, drimane, and coloratane type sesquditerpenoids amongst which are ugandensial, warburganal, mukaadial, and other secondary metabolites, such as tannins, flavonoids, saponins, steroids, and mannitol. This group of compounds gives the plant a high therapeutic value. Based on the review, there is a need for identification and isolation of the highly therapeutic phytochemical constituents and a drive for more preclinical and clinical trials to validate the safety and efficacy of the extracts. This gives basis for the potential development of new therapeutic drugs from the plant.

Iso-Mukaadial Acetate from Warburgia salutaris Enhances Glucose Uptake in the L6 Rat Myoblast Cell Line

Diabetes mellitus (DM) is a chronic metabolic disorder which has become a major risk to the health of humankind, as its global prevalence is increasing rapidly. Currently available treatment options in modern medicine have several adverse effects. Thus, there is an urgent need to develop alternative cost-effective, safe, and active treatments for diabetes. In this regard, medicinal plants provide the best option for new therapeutic remedies desired to be effective and safe. Recently, we focused our attention on drimane sesquiterpenes as potential sources of antimalarial and antidiabetic agents. In this study, iso-mukaadial acetate (Iso) (1), a drimane-type sesquiterpenoid from the ground stem bark of Warburgia salutaris, was investigated for glucose uptake enhancement in the L6 rat myoblast cell line. In vitro assays with L6 skeletal muscle cells were used to test for cytotoxicity, glucose utilisation, and western blot analysis. Additionally, the inhibition of carbohydrate digestive enzymes and 1,1-diphenyl-2- picrylhydrazyl (DPPH) scavenging activity were analysed in vitro. The cell viability effect of iso-mukaadial acetate was the highest at 3 µg/mL with a percentage of 98.4. Iso-mukaadial acetate also significantly and dose-dependently increased glucose utilisation up to 215.18% (12.5 µg/mL). The increase in glucose utilisation was accompanied by enhanced 5' adenosine monophosphate-activated protein kinase (AMPK)and protein kinase B (AKT) in dose-dependent manner. Furthermore, iso-mukaadial acetate dose-dependently inhibited the enzymes α-amylase and α-glucosidase. Scavenging activity against DPPH was displayed by iso-mukaadial acetate in a concentration-dependent manner. The findings indicate the apparent therapeutic efficacy of iso-mukaadial acetate isolated from W. salutaris as a potential new antidiabetic agent.

Bioassay-guided isolation of three anthelmintic compounds from Warburgia ugandensis Sprague subspecies ugandensis, and the mechanism of action of polygodial

Parasitic helminths continue to pose problems in human and veterinary medicine, as well as in agriculture. Resistance to current anthelmintics has prompted the search for new drugs. Anthelmintic metabolites from medicinal plants could be good anthelmintic drug candidates. However, the compounds active against nematodes have not been identified in most medicinal plants with anthelmintic activity. In this study, we aimed to identify the active compounds against helminths in Warburgia ugandensis Sprague subspecies ugandensis (Canellaceae) and study the underlying mechanism of action. A bioassay-guided isolation of anthelmintic compounds from the plant was performed using a Caenorhabditis elegans (C. elegans) test model with a WMicrotracker instrument to monitor motility. Three active compounds were purified and identified by nuclear magnetic resonance and high resolution MS: warburganal (IC₅₀: 28.2 ± 8.6 μM), polygodial (IC₅₀: 13.1 ± 5.3 μM) and alpha-linolenic acid (ALA, IC₅₀: 70.1 ± 17.5 μM). A checkerboard assay for warburganal and ALA as well as polygodial and ALA showed a fractional inhibitory concentration index of 0.41 and 0.37, respectively, suggesting that polygodial and ALA, as well as warburganal and ALA, have a synergistic effect against nematodes. A preliminary structure-activity relationship study for polygodial showed that the α,β-unsaturated 1,4-dialdehyde structural motif is essential for the potent activity. None of a panel of C. elegans mutant strains, resistant against major anthelmintic drug classes, showed significant resistance to polygodial, implying that polygodial may block C. elegans motility through a mechanism which differs from that of currently marketed drugs. Further measurements showed that polygodial inhibits mitochondrial ATP synthesis of C. elegans in a dose-dependent manner (IC₅₀: 1.8 ± 1.0 μM). Therefore, we believe that the underlying mechanism of action of polygodial is probably inhibition of mitochondrial ATP synthesis. In conclusion, polygodial could be a promising anthelmintic drug candidate worth considering for further development.

A review of ethnoboatany, therapeutic value, phytochemistry and pharmacology of Crinum macowanii Baker: A highly traded bulbous plant in Southern Africa

ETHNOPHARMACOLOGICAL RELEVANCE

Crinum macowanii is a deciduous bulbous plant which grows in east, central and southern Africa. Crinum macowanii has been used as herbal medicine by the indigenous people of east and southern Africa has for several centuries. The bulb, leaves and roots of C. macowanii are reported to possess diverse medicinal properties and used to treat or manage various human and animal diseases and ailments throughout its distributional range. Crinum macowanii is used traditionally as a remedy for boils, diarrhoea, fever, inflammation, respiratory system problems, skin rashes, tuberculosis, wounds and urinary tract problems.

AIM OF THE REVIEW

The present review aims to summarize comprehensively the research that has been done on the ethnomedicinal uses, botany, phytochemistry and pharmacology of C. macowanii in different locations throughout its geographical range in east, central and southern African region so as to highlight research gaps and provide a foundation for further investigations on the plant species.

MATERIALS AND METHODS

A review of the literature was undertaken and an in-depth analysis of previous research on ethnobotany, therapeutic value, phytochemistry and pharmacology of C. macowanii throughout its distributional range in east, central and southern Africa. Literature sources included papers published in international journals, reports from international, regional and national organizations, conference papers, books, theses, websites and other grey literature. Electronic search engines such as Google, Google scholar, publishing sites such as Elsevier, scienceDirect, BMC, PubMed and other scientific database sites such as ChemSpider, PubChem were used as well as searching the library collections of the National Herbarium and Botanic Gardens (SRGH), Harare, Zimbabwe and the University of Fort Hare, South Africa.

RESULTS

A total of 32 ethnomedicinal uses of C. macowanii are documented in literature, which can be grouped into seven major ethnomedicinal general purpose usages, namely "fever", "wounds, sores and skin rashes", "boils and inflammation", "respiratory system problems", "blood cleansing", "urinary tract problem" and "veterinary uses". The chemical composition of C. macowanii is dominated by various isoquinoline alkaloids, which have been isolated from the bulbs, flowering stalks, leaves and roots. Major biological activities demonstrated by C. macowanii include antifungal, antiviral and antiplasmodial activities, cardiovascular effects as well as effects on the central nervous system. The population of C. macowanii is declining in the wild as the bulbs are over-collected for sale in medicinal (muthi) markets in southern Africa.

CONCLUSION

A literature search revealed that C. macowanii has a lot of potential as a possible source of pharmaceutical products for the treatment of a wide range of human and animal diseases and ailments. Some of the alkaloids isolated from C. macowanii have demonstrated various biological activities when investigated in in vitro assays. However, some of the ethnomedicinal uses of C. macowanii still require pharmacological investigations. Therefore, further studies are required to improve our knowledge about the mechanisms of action, efficacy, toxicity and clinical relevance of the plant species as well as its bioactive compounds.

De Novo Transcriptome Analysis of Warburgia ugandensis to Identify Genes Involved in Terpenoids and Unsaturated Fatty Acids Biosynthesis

The bark of Warburgia ugandensis (Canellaceae family) has been used as a medicinal source for a long history in many African countries. The presence of diverse terpenoids and abundant polyunsaturated fatty acids (PUFAs) in this organ contributes to its broad range of pharmacological properties. Despite its medicinal and economic importance, the knowledge on the biosynthesis of terpenoid and unsaturated fatty acid in W. ugandensis bark remains largely unknown. Therefore, it is necessary to construct a genomic and/or transcriptomic database for the functional genomics study on W. ugandensis. The chemical profiles of terpenoids and fatty acids between the bark and leaves of W. ugandensis were compared by gas chromatography-mass spectrometry (GC-MS) analysis. Meanwhile, the transcriptome database derived from both tissues was created using Illumina sequencing technology. In total, about 17.1 G clean nucleotides were obtained, and de novo assembled into 72,591 unigenes, of which about 38.06% can be aligned to the NCBI non-redundant protein database. Many candidate genes in the biosynthetic pathways of terpenoids and unsaturated fatty acids were identified, including 14 unigenes for terpene synthases. Furthermore, 2,324 unigenes were discovered to be differentially expressed between both tissues; the functions of those differentially expressed genes (DEGs) were predicted by gene ontology enrichment and metabolic pathway enrichment analyses. In addition, the expression of 12 DEGs with putative roles in terpenoid and unsaturated fatty acid metabolic pathways was confirmed by qRT-PCRs, which was consistent with the data of the RNA-sequencing. In conclusion, we constructed a comprehensive transcriptome dataset derived from the bark and leaf of W. ugandensis, which forms the basis for functional genomics studies on this plant species. Particularly, the comparative analysis of the transcriptome data between the bark and leaf will provide critical clues to reveal the regulatory mechanisms underlying the biosynthesis of terpenoids and PUFAs in W. ugandensis.

Warburgia: a comprehensive review of the botany, traditional uses and phytochemistry

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Warburgia (Canellaceae) is represented by several medicinal trees found exclusively on the African continent. Traditionally, extracts and products produced from Warburgia species are regarded as important natural African antibiotics and have been used extensively as part of traditional healing practices for the treatment of fungal, bacterial and protozoal infections in both humans and animals. We here aim to collate and review the fragmented information on the ethnobotany, phytochemistry and biological activities of ethnomedicinally important Warburgia species and present recommendations for future research.

MATERIALS AND METHODS

Peer-reviewed articles using "Warburgia" as search term ("all fields") were retrieved from Scopus, ScienceDirect, SciFinder and Google Scholar with no specific time frame set for the search. In addition, various books were consulted that contained botanical and ethnopharmacological information.

RESULTS

The ethnopharmacology, phytochemistry and biological activity of Warburgia are reviewed. Most of the biological activities are attributed to the drimane sesquiterpenoids, including polygodial, warburganal, muzigadial, mukaadial and ugandensial, flavonoids and miscellaneous compounds present in the various species. In addition to anti-infective properties, Warburgia extracts are also used to treat a wide range of ailments, including stomach aches, fever and headaches, which may also be a manifestation of infections. The need to record anecdotal evidence is emphasised and conservation efforts are highlighted to contribute to the protection and preservation of one of Africa's most coveted botanical resources.