R. Waibel’s research while affiliated with Universitätsklinikum Erlangen and other places

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Publications (16)


The dichapetalins - Unique cytotoxic constituents of the dichapetalaceae in phytochemicals as nutraceuticals
  • Article

January 2012

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11 Reads

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1 Citation

InTech

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M.A. Chama

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R. Waibel

ChemInform Abstract: Constituents of Tropical Medicinal Plants. Part 69. The Hexalobines, Diprenylated Indoles from Hexalobus crispiflorus and Hexalobus monopetalus.

October 2010

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26 Reads

ChemInform

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.


ChemInform Abstract: Synthetic and Spectroscopic Studies with Nb-Substituted Hexahydrocanthin-6-ols and Their Acid-Catalyzed Dimerization.

March 2010

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7 Reads

ChemInform

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.


ChemInform Abstract: Constituents of Tropical Medicinal Plants. Part 87. Rosane Diterpenes and Bis-Dinorditerpenes from Hugonia casteneifolia

February 2010

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45 Reads

ChemInform

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R. WAIBEL

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M. H. H. NKUNYA

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[...]

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H. ACHENBACH

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.


ChemInform Abstract: Constituents of Tropical Medicinal Plants. Part 74. Dichapetalins - A New Class of Triterpenoids
  • Article
  • Full-text available

January 2010

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36 Reads

ChemInform

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Download

ChemInform Abstract: Constituents of Tropical Medicinal Plants. Part 75. Absolute Configuration of Dichapetalin A

January 2010

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23 Reads

ChemInform

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.


Fig. 2: HMBC in 1 indicated by doubleheaded arrow 
Fig. 4: Graph of ratio of % protection to % survival against conc. of crude aqueous extract 
Fig. 5: Graph of ratio of % protection to % survival against conc. of hispidulin 
Hispidulin And Other Constituents Of Scoparia dulcis Linn

September 2009

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1,503 Reads

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26 Citations

Journal of Science and Technology (Ghana)

Phytochemical investigation of the ethanol extract of the whole plant of Scoparia dulcis, has resulted in the isolation of 4, 5, 7-trihydroxy-6-methoxyflavone, commonly called hispidulin and a steroidal glycoside, β-sitosterol-β-D-glucoside. This is the first isolation of the two compounds from S. dulcis. Also isolated and characterized were the previously reported 6-me-thoxybenzoxazolinone, friedelan-3-one and scopadulcic acid B. Structural elucidation was done on the basis of spectroscopic data interpretations (IR, UV, NMR and EIMS). Using the Tetrazolium-based colorimetric selective assay, hispidulin was found to be inactive against HIV-1/IIIB in MT-4 cells whereas the same test on the aqueous extract of the plant was positive.



New Diprenylated Indoles from Asteranthe Asterias (Annonaceae)

October 1996

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30 Reads

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15 Citations

Natural Product Letters

Two new diprenylated indoles, 2′,3′-epoxyasteranthine and 2′,3′-dihydroxyasteranthine, were isolated from the stem bark and the root bark of Asteranthe asterias (Annonaceae). Their structures were elucidated by spectroscopic methods. Each of the two compounds was obtained in an enantiomeric ratio of 3:1 (S/R) and exhibited antimycotic activity against Saprolegnia and Rhizoctonia species.


Dichapetalin A, A Novel Plant Constituent from Dichapetalum madagascariense With Potential Antineoplastic Activity

September 1995

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107 Reads

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33 Citations

Natural Product Letters

From the roots of Dichapetalum madagascariense (Dichapetalaceae) dichapetalin A, a plant constituent with a new basic skeleton, has been isolated. Its structure was elucidated by spectroscopic methods. In-vitro experiments revealed a strong and selective cytotoxicity.


Citations (7)


... Preliminary antibacterial and antifungal evaluation was also performed on the ethanolic leaf extract of Brazilian C. regium [13]. Secondary metabolites identified in C. tinctorium include triterpenes (alphitolic acid & 3-O-E-p-coumaroylalphitolic acid), apocarotenes (cochloxanthin & dihydrocochloxanthin), as well as triacylbenzenes (e.g., 1,3,5-tri[dodecanyl]-& tri[tetradecanyl]benzenes, also isolated from C. angolensis, C. planchonii, and C. tinctorium) and volatile ketones, such as 1-hydroxytetradecan-3-one [10,[14][15][16]. Gas chromatography/mass spectrometry (GC/MS) analysis of essential oil of the leaves, root bark, and root wood of C. vitifolium resulted in the identification of α-humulene, β-caryophyllene, β-bisabolene, β-pinene, γ-muurolene, and 1-hydroxy-3-hexadecanone. ...

Reference:

Hydroxybenzoic Acids Are Significant Contributors to the Antioxidant Effect of Borututu Bark, Cochlospermum angolensis Welw. ex Oliv
ChemInform Abstract: CONSTITUENTS OF WEST AFRICAN MEDICINAL PLANTS, XVI. NOVEL LONG-CHAIN TRIACYLBENZENES FROM COCHLOSPERMUM PLANCHONII
  • Citing Article
  • October 1985

Chemischer Informationsdienst

... The phytochemical analysis in the current study confirmed the presence of flavonoids, saponins, phenolic compounds and terpenes in these crude extracts (Table 2). Previous phytochemical analysis studies from these plants revealed the presence of phytosterols, 36 terpenes, 37 triterpenoids, 37-40 diterpenoids 41-43 and phenolic compounds 36,38 and fatty acids. 44 The difference in the cytotoxicity in these extracts could be attributed to the phytochemical ratios of tannins, alkaloids, flavonoids, phenols, and terpenoids in them. ...

Constituents of the stem bark and twigs of Croton macrostachy(u)s
  • Citing Article
  • January 1992

... The dichapetalins constitute a small family of secondary metabolites of mixed biosynthesis, composed of a dammarane part and a C 6 -C 2 unit. Dichapetalin A was the first to be discovered and was isolated from the roots of Dichapetalum madagascariense (Achenbach et al., 1995;Osei-Safo et al., 2012). It presented a very potent cytotoxic effect against L1210 murine leukemia cells, with an EC90 below 1.7 Â 10 À10 M, but was four orders of magnitude less efficient towards KB carcinoma cells and murine bone marrow cells stimulated with GM-CSF (granulocyte-macrophage colony-stimulating factor). ...

The dichapetalins - Unique cytotoxic constituents of the dichapetalaceae in phytochemicals as nutraceuticals
  • Citing Article
  • January 2012

InTech

... collected in Brazil, [28] aerial parts ethanolic extract of Astragalus annularis Forssk. and Astragalus trimestris L. from Egypt, [29] leaf methanol extract of Plantago asiatica L. [30] It was also mentioned in Scoparia dulcis L. collected in Ghana, [31] Ruellia tuberosa L. from Taiwan flora, [32] Thymus herba barona and Mentha x piperita collected in France, [33] as well as in the root benzene extract of Spathelia sorbifolia L. from Jamaica, [34] and Sorbaria sorbifolia L. collected in Ukraine. [35] Because most plants that contain sorbifolin as a major component belong to the Fabaceae and Lamiaceae families, it may be deduced that this molecule is their chemotype ( Table 1). ...

Hispidulin And Other Constituents Of Scoparia dulcis Linn

Journal of Science and Technology (Ghana)

... The further new alkaloids, correantines A (3) and B (4), 20-epi-correantine B (5) and correantine C (6) were isolated as minor compounds, besides the known terpenoids $, 9 and lutein. Furthermore, 10-hydroxycorreantoside (7) was precipitated with Mayer's reagent from the aqueous layer (Table 1). ...

New Alkaloids from the Leaves of Cephaelis correae

Planta Medica

... It is also used to treat diabetes in pregnant women in Benin and hypertension [8] . In addition, à molecule called Dichapetain A has been isolated from the root of the plant in Ghana [9] . Despite its widespread use, little toxicological data are available on the safety of repeated exposure to D. guineense leaves. ...

Dichapetalin A, A Novel Plant Constituent from Dichapetalum madagascariense With Potential Antineoplastic Activity
  • Citing Article
  • September 1995

Natural Product Letters

... The prenylated indole alkaloids are generally referred to as 'hexalobines' due to their marked presence in the genus Hexalobus Malebo et al., 2014), making them useful as chemotaxonomic markers for this genus. Moreover, this class of compounds have been exclusively isolated from certain genera in the family Annonaceae including Hexalobus, Isolona (Achenbach and Löwel, 1995;Nkunya et al., 2004), Monodora (Adeoye et al., 1986;Nkunya et al., 2004), Asteranthe (Nkunya et al., 1996) and Uvaria (Achenbach and Raffelsberger, 1979), thus extending their chemotaxonomic importance beyond the genus Hexalobus to other closely related genera. This characteristic accumulation of prenylated indole alkaloids in specific genera supports a molecular phylogenetic study on African Annonaceae which revealed Hexalobus, Uvariastrum, Asteranthe, Isolona and Monodora to belong as one sub-clade in the African long-branch clade (ALBC) (Botermans et al., 2011;Couvreur et al., 2008). ...

New Diprenylated Indoles from Asteranthe Asterias (Annonaceae)
  • Citing Article
  • October 1996

Natural Product Letters