Isolation and Structure Characterization of Flavonoids

Flavonoids are one of the most important classes of secondary metabolites from natural products due to their several applications in medicine, foods, diet industries, and so on. Even though a huge number has been reported from natural and synthetic sources, scientists are still interested in flavonoids and derivatives. The biggest challenge for working on secondary metabolites is related to the use of the predicted theoretical method to isolate the expected compound and finally analyse the spectroscopic data to elucidate and fully characterize the structure. This chapter was designed to document useful techniques for isolation and structure characterization of flavonoids. Besides the well-known methods that have been used so far, we would also put together updated information about novel challenge techniques published in recent articles on isolation and characterization of flavonoids. Our data were obtained mainly from academic library and from reported data online by using research links such as Google Scholar, Scopus, SciFinder, Scirus, PubMed, and so on. Our field experience on phytochemistry of isolation and characterization of flavonoids was also used in this chapter

In Vitro Antiplasmodial Activity and Cytotoxicity of Extracts of Selected Medicinal Plants Used by Traditional Healers of Western Cameroon

Medicinal plants play a key role in malaria control in Africa, especially in remote areas where health facilities are limited. In order to assess their acclaimed potentials, eleven extracts were prepared from seven selected plants commonly used in Western Cameroon, and tested both for their antiplasmodial activity and cytotoxicity. The antiplasmodial activity was assessed using Lactate Dehydrogenase Assay (pLDH) and the cytotoxicity estimated on LLC-MK2 monkey kidney epithelial cells. Seven extracts from five different plants were significantly active, with very weak or no cytotoxicity. The Dacryodes edulis leaves showed the highest activity (IC50 of 6.45 μg/mL on 3D7 and 8.2 μg/mL on DD2) followed by the leaves of Vernonia amygdalina (IC50 of 8.72 and 11.27 μg/mL on 3D7 and DD2 resp.) and roots of V. amygdalina (IC50 of 8.72 μg/mL on 3D7), Coula edulis leaves (IC50 of 13.80 μg/mL and 5.79 μg/mL on 3D7 and DD2 resp.), Eucalyptus globulus leaves (IC50 of 16.80 μg/mL and 26.45 μg/mL on 3D7 and DD2) and Cuviera longiflora stem bark (IC50 of 20.24 μg/mL and 13.91 μg/mL on 3D7 and DD2). These findings justify the use of five of the seven plants in malaria treatment by traditional healers of Western Cameroon

Antimicrobial activity and cytotoxicity of the ethanol extract, fractions and eight compounds isolated from Eriosema robustum (Fabaceae)

BACKGROUND: The aim of this study was to evaluate the antimicrobial activity and the cytotoxicity of the ethanol crude extract, fractions and isolated compounds from the twigs of Eriosema robustum, a plant used for the treatment of coughs and skin diseases. METHODS: Column chromatographic and spectroscopic techniques were used to isolate and identify eight compounds, robusflavones A (1) and B (2), orostachyscerebroside A (3), stigmasterol (4), 1-O-heptatriacontanoyl glycerol (5), eicosanoic acid (6), 3-O-β-D-glucopyranoside of sitosterol (7) and 6-prenylpinocembrin (8), from E. robustum. A two-fold serial microdilution method was used to determine the minimum inhibitory concentration (MIC) against fungi and bacteria, and the 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide reduction assay was used to evaluate the cytotoxicity. RESULTS: Fraction B had significant antimicrobial activity against Aspergillus fumigatus and Cryptoccocus neoformans (MIC 0.08 mg/ml), whilst the crude extract and fraction A had moderate activity against A. fumigatus and Candida albicans (MIC 0.16 mg/ml). Fraction A however had excellent activity against Staphylococcus aureus (MIC 0.02 mg/ml), Enterococcus faecalis and Escherichia coli (MIC 0.04 mg/ml). The crude extract had significant activity against S. aureus, E. faecalis and E. coli. Fraction B had good activity against E. faecalis and E. coli (MIC 0.08 mg/ml). All the isolated compounds had a relatively weak antimicrobial activity. An MIC of 65 μg/ml was obtained with robusflavones A (1) and B (2) against C. albicans and A. fumigatus, orostachyscerebroside A (3) against A. fumigatus, and robusflavone B (2) against C. neoformans. Compound 8 had the best activity against bacteria (average MIC 55 μg/ml). The 3 fractions and isolated compounds had LC50 values between 13.20 to > 100 μg/ml against Vero cells yielding selectivity indices between 0.01 and 1.58. CONCLUSION: The isolated compounds generally had a much lower activity than expected based on the activity of the fractions from which they were isolated. This may be the result of synergism between different compounds in the complex extracts or fractions. The results support the traditional use of E. robustum to treat infections. The crude extract had a good activity and low preparation cost, and may be useful in topical applications to combat microbial infections.The authors are grateful to the University of Pretoria for the Post-doctoral Fellowship awarded to MD Awouafack to work at the Faculty of Veterinary Science, Department of Paraclinical Sciences, Phytomedicine Programme, and the National Research Foundation and Medical Research Council for research funding.http://www.biomedcentral.com/1472-6882/13/289am2014mn201

Antimicrobial and antioxidant activities of extracts and ten compounds from three Cameroonian medicinal plants : Dissotis perkinsiae (Melastomaceae), Adenocarpus mannii (Fabaceae) and Barteria fistulosa (Passifloraceae)

BACKGROUND : We decided to investigate the antimicrobial and the antioxidant activities of extracts and compounds isolated from Dissotis perkinsiae, Adenocarpus mannii and Barteria fistulosa, three Cameroonianmedicinal plants used for the treatment of skin diseases, wounds, fever, rheumatism, malaria and/or infectious diseases. METHODS : Standard chromatographic and spectroscopic methods were used to isolate and identify ten compounds from the three plant species [1–5 (from D. perkinsiae), 2, 6–8 (from A. mannii) and 2, 4, 9, and 10 (fromB. fistulosa)]. A two-fold serial microdilutionmethod was used to determine the minimuminhibitory concentration (MIC) against a panel of fungal and bacterial species. The radical scavenging capacity using 2,2- diphenyl-1-picryhydrazyl (DPPH) was determined to evaluate the antioxidant activity of the samples. RESULTS : The compounds isolated were: ursolic acid (1), oleanolic acid (2), quercetin 3-O-(6″-O-galloyl)- β-galactopyranoside (3), 3-O-β-D-glucopyranoside of sitosterol (4), ellagic acid (5), isoprunetin (6), chrysin 7-O- β-D-glucopyranoside (7), isovitexin (8), hederagenin (9) and shanzhiside methyl ester (10). The ethanol extract of D. perkinsiae had good antibacterial activity against Enterococcus faecalis (MICs 0.04 and 0.08 mg/ml), Escherichia coli (MIC 0.08 mg/ml) and Staphylococcus aureus (MIC 0.08 mg/ml). The extract of B. fistulosa had significant antifungal activity against Cryptococcus neoformanswith an MIC of 0.08 mg/ml. Other extracts hadmoderate to poor antimicrobial activities with the MIC ranging from 0.16 to 2.50 mg/ml. The isolated compounds were generally more active against bacteria (MIC ranging from 16 to 250 μg/ml) than fungi (MIC between 31 and 250 μg/ml). Moderate antibacterial activity was obtained with compound 3 against E. faecalis and E. coli (MIC of 16 μg/ml in both cases), compounds 6 and 10 against E. faecalis (MIC of 16 μg/ml), and compound 9 against E. faecalis (MIC 31 μg/ml) and S. aureus (MIC 31 μg/ml). The B. fistulosa extract had the greatest radical scavenging activity (IC50 100.16 μg/ml) followed by extracts of D. perkinsiae (IC50 130.66 μg/ml), and A. mannii (IC50 361.30 μg/ml). Compounds 3 and 5 had significant antioxidant activities with the IC50 of 9.84 and 9.99 μg/ml as compared to that of ascorbic acid (IC50 2.41 μg/ml). CONCLUSION : The results obtained support the traditional use of the three plant species (D. perkinsiae, A. mannii and B. fistulosa) in traditional medicine for the treatment of infections. Some extracts and isolated compounds could be useful in development of antimicrobial agents.We are currently investigating the toxicity and other pharmacological activities with the potential use as topical antimicrobial agents.University of Dschang. The NRF and the University of Pretoria for the Postdoctoral Fellowship awarded to work at the Phytomedicine Programme, Department of Paraclinical Sciences, Faculty of Veterinary Science.http://www.elsevier.com/locate/sajbhb201

Anti‑inflammatory and acetylcholinesterase activity of extract, fractions and five compounds isolated from the leaves and twigs of Artemisia annua growing in Cameroon

BACKGROUND : Natural products, including those derived from higher plants have, over the years, contributed greatly to the development of modern therapeutic drugs. Due to the medicinal importance in traditional practice and the diversified biology and chemistry of the constituents from Artemisia spp., the genus has been receiving growing attention. The aim of this study was to investigate the ability of the ethanol extract, four fractions (F1–F4) and five compounds namely artemisinin (1), scopoletin (2), chrysosplenetin (3), eupatin (4) and 3-O-β-d-glucopyranoside of sitosterol (5) isolated from A. annua to modulate the activity of anticholinesterase (AchE) and the production of nitric oxide (NO) in LPS-activated RAW 264.7 macrophages. RESULTS : At the lowest concentration tested (6.25 μg/mL), the crude extract and fraction F2 had the highest NO inhibitory activity (72.39 and 71.00 % inhibition respectively) without significant toxicity on the viability of macrophage cells (93.86 and 79.87 % of cell viability respectively). The crude extract inhibited AchE activity by 71.83 % (at 1 mg/mL) with an IC50 value of 87.43 μg/mL while F2 and F4 were the most active fractions (IC50 values of 36.75 and 28.82 μg/mL). Artemisinin (1) and chrysosplenetin (3) had the highest AChE activity with 71.67 and 80.00 % inhibition (at 0.1 mg/mL) and IC50 values of 29.34 and 27.14 μg/mL, respectively. CONCLUSION : Our results validate the traditional use of A. annua and could help to support the usefulness of this plant in the treatment of inflammatory and neurological disorders especially where nitric oxide and a cholinesterase are involved.The National Research Foundation (NRF) and Medical Research Council (MRC) provided funding to support this study. The Université des Montagnes provided financial support to phytochemical experimental part of this work.http://www.springerplus.comam2016Paraclinical Science

Antiplasmodial Activities of Some Products from Turreanthus Africanus (Meliaceae)

We investigated the antiplasmodial activity of some pure compounds of Turreanthus africanus (Meliaceae), a plant that is used in traditional medicine to treat malaria in Southwest Cameroon. A phytochemical analysis of the methylene chloride: methanol (1:1) extract of the seeds of the plant yielded seven compounds. Four of them, which were oils, were subjected to in vitro bioassays on Plasmodium falciparum F 32, chloroquine sensitive strain. Compound 1 (16-oxolabda-8 (17), 12(E)-dien-15-oic acid), showed the highest antiplasmodial activity, two others (methyl-14,15-epoxylabda-8 (17), 12(E)-diene-16-oate, and turreanin A), had moderate activity and one was inactive. These findings are consistent with the use of T. africanus in the traditional treatment of P. falciparum malaria

Antimicrobial and antioxidant activity of kaempferol rhamnoside derivatives from Bryophyllum pinnatum

Abstract Background Bryophyllum pinnatum (Lank.) Oken (Crassulaceae) is a perennial succulent herb widely used in traditional medicine to treat many ailments. Its wide range of uses in folk medicine justifies its being called "life plant" or "resurrection plant", prompting researchers' interest. We describe here the isolation and structure elucidation of antimicrobial and/or antioxidant components from the EtOAc extract of B. pinnatum. Results The methanol extract displayed both antimicrobial activities with minimum inhibitory concentration (MIC) values ranging from 32 to 512 μg/ml and antioxidant property with an IC50 value of 52.48 μg/ml. Its partition enhanced the antimicrobial activity in EtOAc extract (MIC = 16-128 μg/ml) and reduced it in hexane extract (MIC = 256-1024 μg/ml). In addition, this process reduced the antioxidant activity in EtOAc and hexane extracts with IC50 values of 78.11 and 90.04 μg/ml respectively. Fractionation of EtOAc extract gave seven kaempferol rhamnosides, including; kaempferitrin (1), kaempferol 3-O-α-L-(2-acetyl)rhamnopyranoside-7-O-α-L-rhamnopyranoside (2), kaempferol 3-O-α-L-(3-acetyl)rhamnopyranoside-7-O-α-L-rhamnopyranoside (3), kaempferol 3-O-α-L-(4-acetyl)rhamnopyranoside-7-O-α-L-rhamnopyranoside (4), kaempferol 3-O-α-D- glucopyranoside-7-O-α-L-rhamnopyranoside (5), afzelin (6) and α-rhamnoisorobin (7). All these compounds, except 6 were isolated from this plant for the first time. Compound 7 was the most active, with MIC values ranging from 1 to 2 μg/ml and its antioxidant activity (IC50 = 0.71 μg/ml) was higher than that of the reference drug (IC50 = 0.96 μg/ml). Conclusion These findings demonstrate that Bryophyllum pinnatum and some of its isolated compounds have interesting antimicrobial and antioxidant properties, and therefore confirming the traditional use of B. pinnatum in the treatment of infectious and free radical damages.</p

Anticancer Activities of Six Selected Natural Compounds of Some Cameroonian Medicinal Plants

BACKGROUND: Natural products are well recognized as sources of drugs in several human ailments. In the present work, we carried out a preliminary screening of six natural compounds, xanthone V(1) (1); 2-acetylfuro-1,4-naphthoquinone (2); physcion (3); bisvismiaquinone (4); vismiaquinone (5); 1,8-dihydroxy-3-geranyloxy-6-methylanthraquinone (6) against MiaPaCa-2 pancreatic and CCRF-CEM leukemia cells and their multidrug-resistant subline, CEM/ADR5000. Compounds 1 and 2 were then tested in several other cancer cells and their possible mode of action were investigated. METHODOLOGY/FINDINGS: The tested compounds were previously isolated from the Cameroonian medicinal plants Vismia laurentii (1, 3, 4, 5 and 6) and Newbouldia laevis (2). The preliminary cytotoxicity results allowed the selection of xanthone V(1) and 2-acetylfuro-1,4-naphthoquinone, which were then tested on a panel of cancer cell lines. The study was also extended to the analysis of cell cycle distribution, apoptosis induction, caspase 3/7 activation and the anti-angiogenic properties of xanthone V(1) and 2-acetylfuro-1,4-naphthoquinone. IC(50) values around or below 4 µg/ml were obtained on 64.29% and 78.57% of the tested cancer cell lines for xanthone V(1) and 2-acetylfuro-1,4-naphthoquinone, respectively. The most sensitive cell lines (IC(50)<1 µg/ml) were breast MCF-7 (to xanthone V(1)), cervix HeLa and Caski (to xanthone V(1) and 2-acetylfuro-1,4-naphthoquinone), leukemia PF-382 and melanoma colo-38 (to 2-acetylfuro-1,4-naphthoquinone). The two compounds showed respectively, 65.8% and 59.6% inhibition of the growth of blood capillaries on the chorioallantoic membrane of quail eggs in the anti-angiogenic assay. Upon treatment with two fold IC(50) and after 72 h, the two compounds induced cell cycle arrest in S-phase, and also significant apoptosis in CCRF-CEM leukemia cells. Caspase 3/7 was activated by xanthone V(1). CONCLUSIONS/SIGNIFICANCE: The overall results of the present study provided evidence for the cytotoxicity of compounds xanthone V(1) and 2-acetylfuro-1,4-naphthoquinone, and bring supportive data for future investigations that will lead to their use in cancer therapy