Antibacterial and Antioxidant Properties of the Methanolic Extract of the Stem Bark of Pteleopsis hylodendron (Combretaceae)

Pteleopsis hylodendron (Combretaceae) is used in Cameroon and West Africa folk medicine for the treatment of various microbial infections (measles, chickenpox, and sexually transmitted diseases). The antibacterial properties of the methanolic extract and fractions from stem bark of Pteleopsis hylodendron were tested against three Gram-positive bacteria and eight Gram-negative bacteria using Agar-well diffusion and Broth microdilution methods. Antioxidant activities of the crude extract and fractions were investigated by DPPH radical scavenging activity and β-carotene-linoleic acid assays. The methanolic extract and some fractions exhibited antibacterial activities that varied between the bacterial species (ID = 0.00–25.00 mm; MIC = 781–12500 μg/mL and 0.24–1000 μg/mL). The activity of the crude extract is, however, very weak compared to the reference antibiotics (MIC = 0.125–128 μg/mL). Two fractions (FE and FF) showed significant activity (MIC = 0.97 μg/mL) while S. aureus ATCC 25922 was almost resistant to all the tested fractions. In addition, the crude extract and some fractions showed good antioxidant potential with inhibition values ranging from 17.53 to 98.79%. These results provide promising baseline information for the potential use of this plant as well as some of the fractions in the treatment of infectious diseases and oxidative stress

Phytochemical investigation and biological activities of Lantana rhodesiensis

peer reviewedLantana rhodesiensis Moldenke is a plant widely used to treat diseases, such as rheumatism, diabetes, and malaria in traditional medicine. To better understand the traditional uses of this plant, a phytochemical study was undertaken, revealing a higher proportion of polyphenols, including flavonoids in L. rhodesiensis leaf extract and moderate proportion in stem and root extracts. The antioxidant activity of the extracts was also determined using three different assays: the radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity, the FRAP method (Ferric-reducing antioxidant power) and the β-carotene bleaching test. The anti-malarial activity of each extract was also evaluated using asexual erythrocyte stages of Plasmodium falciparum, chloroquine-sensitive strain 3D7. The results showed that the leaf extract exhibited higher antioxidant and anti-malarial activities in comparison with the stem and root extracts, probably due to the presence of higher quantities of polyphenols including flavonoids in the leaves. A positive linear correlation was established between the phenolic compound content (total polyphenols including flavonoids and tannins; and total flavonoids) and the antioxidant activity of all extracts. Furthermore, four flavones were isolated from leaf dichloromethane and ethyl acetate fractions: a new flavone named rhodescine (5,6,3’,5’-tetrahydroxy-7,4’-dimethoxyflavone) (1), 5-hydroxy-6,7,3’,4’,5’-pentamethoxyflavone (2), 5-hydroxy-6,7,3′,4′-tetramethoxyflavone (3), and 5,6,3’-trihydroxy-7,4’-dimethoxyflavone (4). Their structures were elucidated by 1H, 13C NMR, COSY, HSQC, HMBC, and MS-EI spectral methods. Aside from compound 2, all other molecules were described for the first time in this plant species.EOHUB project 600873EPP-1-2018-1ES-EPPKA2-K

Pentas longiflora Oliv. (Rubiaceae), a plant used in the treatment of Pityriasis Versicolor in Rwanda: Chemical composition and standardization of leaves and roots

In Rwanda, the roots of Pentas longiflora Oliv. (Rubiaceae) have been used for a long time to treat Pityriasis versicolor. However, many people reported the use of leaves instead of roots. This research was conducted to compare the phytochemical composition and establish chromatographic methods for the standardization of roots and leaves extracts of P. longiflora. During this process, three new pentalongin glycosides (pentalonginoside A, pentalonginoside B, and pentalonginoside C) and two known glycosides of the same type (harounoside and clarinoside), as well as rutin, luteolin-7-rutinoside were isolated from methanol extract of leaves. In addition, pentalongin and psychorubrin, previously isolated from ethylacetate roots extract, were also identified in Pentas longiflora ethylacetate leaves extract. The presence of the antifungal compound pentalongin in leaves may explain the traditional use of leaves in the treatment of Pytiriasis versicolor. Furthermore, harounoside, psychorubrin, and pentalongin were selected as markers for HPLC fingerprints of MeOH extract. The accuracy and risk profile demonstrated the reliability of the validated method. In general, considerable variations of concentration in plant metabolites, including pentalongin, were observed between samples from different sites. The content in pentalongin (expressed as juglone) in collected samples ranged between 1.7 and 70.0 mg/100 g. The highest concentration (70.0 ± 17 mg/100 g) was registered in the cultivated samples from Mukoni. This important variation of pentalongin concentrations according to sampling sites, shows that in order to guarantee equivalent efficacy, finished products with P. longiflora should be standardized based on their pentalongin content

Antibacterial and antioxidant activities of the extract and some flavonoids from aerial parts of Echinops Gracilis O. Hoffm. (Asteraceae)

Mortality due to microbial diseases continues to be a major problem in many developing countries. The present study aims to evaluate the antibacterial and antioxidant activities of the ethyl acetate extract and some isolated compounds from aerial parts of Echinops gracilis. The phytochemical study resulted in the isolation of a new flavonoid derivative named apigenin-7-O-(4″-feruloyl)-β-D-glucoside (1), together with 2 known compounds: apigenin-7-O-(4″-trans-p-hydroxycinnamoyl)-β-D-glucoside (2), and apigenin-7-O-glucoside (3). Their chemical structures were determined using a combination of NMR and IR spectroscopic and MS techniques, as well as by comparison with literature data. The extract and isolates were evaluated for their antibacterial and antioxydant properties. The EtOAc extract and compounds 1 and 2 showed the ability to scavenge 2,2′-zino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS) with scavenging concentration (SC50) values of 13.6 ± 0.8 µg/mL, 108.2 ± 4.3 µg/mL, and 28.5 ± 2.2 µg/mL, respectively. In addition, compound 1 displayed significant activity against Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumonia, with minimum inhibition concentration (MIC) values of 31.2, 15.6, and 31.2 µg/mL respectively.https://journals.sagepub.com/home/npxhj2022Chemistr

A new isoquinoline and ceramide from the stem barks of Discoglypremna caloneura (Pax) Prain (Euphorbiaceae) with antiproteinase and cytotoxic activities.

peer reviewedTwo new compounds, an isoquinoline (1) and caloneuramide (2), a ceramide were isolated from the stem bark of Discoglypremna caloneura together with seven known compounds namely aurantiamide acetate (3), acetylaleuritolic acid (4), 3α-hydroxylaleuritolic acid 2α-p-hydroxybenzoate (5), mixture of stigmasterol (6) and β-sitosterol (7), mixture of 7-oxo-stigmasterol (8) and 7-oxo-β-sitosterol (9). Their structures were determined based on data from literature and spectroscopic methods. Derivatization reactions on the isoquinoline led to two new compounds, the methylated (10) and acetylated (11) derivatives. Some compounds and extracts were evaluated for their cytotoxic and antiproteinase activity. Antiproteinase effect of compounds 1, 10 and 11 exhibited IC(50) values of 10.77, 1.19 and 3.61 μg/mL respectively; significantly low compared to the standard drug, acetyl salicylic acid (IC(50) = 20.28 μg/mL). Ethyl acetate and methanol extract exhibited moderate cytotoxicity activity on Chang liver cells with CC(50) values of 167.90 ± 2.20 and 106.30 ± 2.03 μg/mL compared to the reference drug cucurmin (CC(50) = 11.05 ± 1.04 μg/mL)

Terpenoids from Phaulopsis imbricata (Acanthaceae)

The whole plant of Phaulopsis imbricata (Forssk.) Sweet (Acanthaceae) was collected at Bansoa, Cameroon, shade dried and extracted by maceration in methanol. This study was carried out to isolate secondary metabolites from this plant species that has not been investigated so far. Two lupane-type triterpenoids, one β-type carotenoid, one eudesmane-type sesquiterpenoid, and one sterol glycoside were isolated from the dried methanol extract using solvent partitioning, column chromatography and re-crystallization. They were identified as lupeol, betulin, (all-E)-lutein, cryptomeridiol, and sitosterol 3- O-β-D-glucopyranoside, respectively. The structures of the isolated compounds were elucidated on the basis of spectroscopic methods including 1D- and 2D- nuclear magnetic resonance (NMR), infrared (IR) and mass spectrometry (MS). This is the first report of these compounds from the genus Phaulopsis. To the best of our knowledge, P. imbricata is also the first species of the genus to be phytochemically studied

Ethnopharmacology and malaria in Africa

According to the last World Malaria Report [1], there were 584 000 deaths for 198 millions malaria cases worldwide in 2013. Particularly, the disease caused an estimated 437 000 African children died before their fifth birthday, still in 2013. Malaria is caused by a parasite, Plasmodium sp. and transmitted by Anopheles mosquitoes. The problem of parasite resistance towards common available medicines such as chloroquine, mefloquine, quinine, is increasing. In this context, the vegetal kingdom remains the main source of pharmacologically active compounds against this parasitic infection as attested by the famous quinine, isolated from Cinchona sp., artemisinin extracted from Artemisia annua and also atovaquone derived from lapachol found in several Bignoniaceae. All these substances are related to plants with traditional use against fever and malaria. Beside these well-known examples, various new antiplasmodial compounds are frequently discovered from Nature, particularly following an ethnopharmacological approach, as reviewed by several authors in recent years [2-6]. Then, the pharmacological and phytochemical study of plants from traditional pharmacopoeias can be of first interest not only to discover new antimalarial “lead compounds”, but also to valorize local vegetal species whose efficacy and safety would have been demonstrated in laboratory and clinical investigations [7]. As demonstrated in several works from Willcox [8], better knowledge of plants from traditional pharmacopoeias and local valorization of validated traditional remedies in Improved Traditional Medicine (ITM) could allow the access to effective, standardized, available and affordable therapeutics for management of malaria by local populations. After this introductive section, the second part of the talk will be dedicated to the presentation of some results obtained in Liège with Dicoma tomentosa from Burkina-Faso [9], Strychnos icaja from Cameroun [10] and Terminalia mollis from Rwanda [11]. 1. WHO, World Malaria Report 2014, December 2014, Geneva (http://www.who.int/malaria/publications/world_malaria_report_2014/en/). 2. Batista R, Silva Ade J Jr, de Oliveira AB: Plant-derived antimalarial agents: new leads and efficient phytomedicines. Part II. Non-alkaloidal natural products. Molecules 2009, 14:3037-72. 3. Bero J, Frédérich M, Quetin-Leclercq J : Antimalarial compounds isolated from plants used in traditional medicine. Journal of Pharmacy and Pharmacology 2009, 61:1401–1433. 4. Bero J and Quetin-Leclercq J: Natural products published in 2009 from plants traditionally used to treat malaria. Planta Medica 2011, 77:631-40. 5. Kaur K, Jain M, Kaur T, Jain R: Antimalarials from nature. Bioorganic & Medicinal Chemistry 2009, 17:3229–3256. 6. Nogueira CR and Lopes LMX: Antiplasmodial Natural Products. Molecules 2011, 16:2146-2190 7. Ginsburg H and Deharo E: A call for using natural compounds in the development of new antimalarial treatments – an introduction. Malaria Journal 2011, 10 (suppl. 1):S1 8. Willcox M, Graz B, Falquet J, Diakite C, Giani S, Diallo D: A “reverse pharmacology” approach for developing an antimalarial phytomedicine. Malaria journal 2011, 10(suppl1):S8 9. Jansen, O., Tits, M., Angenot, L., Nicolas, J.-P., De Mol, P., Nikiema, J.-B., & Frédérich, M : Anti-plasmodial activity of Dicoma tomentosa (Asteraceae) and identification of urospermal A-15-O-acetate as the main active compound. Malaria Journal 2012, 11, 289. 10. Tchinda, A. T., Jansen, O., Nyemb, J.-N., Tits, M., Dive, G., Angenot, L., & Frédérich, M. Strychnobaillonine, an unsymmetrical bisindole alkaloid with an unprecedented skeleton from Strychnos icaja roots. Journal of Natural Products 2014, 77(4), 1078–82. 11. Muganga, R., Angenot, L., Tits, M., & Frédérich, M : In vitro and in vivo antiplasmodial activity of three Rwandan medicinal plants and identification of their active compounds. Planta Medica 2013, 80(6), 482-489

Ardisikivuoside, a new triterpenoid saponin from Ardisia kivuensis (Mysinaceae)

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Antioxidant Activity of Flavonoids Isolated From the Fruits of Xylopia parviflora (A. Rich.) Benth

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