Dieudonné Njamen

Structure-oriented UHPLC-LTQ Orbitrap-based approach as a dereplication strategy for the identification of isoflavonoids from Amphimas pterocarpoides crude extract

Hyphenated techniques and especially ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS) are nowadays widely employed in natural products research. However, the complex nature of plant extracts complicates considerably the analysis and the identification of their constituents. Nevertheless, new MS analyzers with increased resolving power and accuracy such as the orbital trap (Orbitrap) could facilitate drastically this process. The objective of this study is the development of a new structure-oriented approach based on fast UHPLC-high-resolution (HR)MS and HRMS/MS methodologies for the identification of isoflavonoids in crude extracts. In addition, aims to assist dereplication procedures, to decrease the laborious isolation steps and orient the focused isolation of compounds of interest. As a proof of concept, the methanol extract of the stem bark of Amphimas pterocarpoides (Leguminosae) was selected. Based on chromatographic (retention time, polarity) and spectrometric features (ultraviolet spectra, accurate m/z, proposed elemental composition, ring double bond equivalent, and relative isotopic abundance) as well as HRMS/MS spectra, several isoflavonoids were identified. In order to verify the proposed structures, 11 isoflavonoids were selectively isolated and unambiguously identified using 1&2D nuclear magnetic resonance techniques. Moreover, the isolated isoflavonoids were studied in HRMS/MS level, employing electrospray ionization and atmospheric pressure chemical ionization sources, in both modes. Useful information regarding their fragmentation patterns was obtained, and characteristic diagnostic ions were defined for the identification of methoxylated isoflavones, dihydroisoflavones and 5-hydroxylated isoflavonoids. Based on the current results, the proposed dereplication strategy was verified and could comprise a novel approach for the analysis of crude extracts in the future not only for isoflavonoids but also for other chemical classes of natural products.

Anti-inflammatory and analgesic properties of the stem bark extracts of Erythrophleum suaveolens (Caesalpiniaceae), Guillemin & Perrottet.

The MeOH stem bark extract of Erythrophleum suaveolens dissolved in water and shaken up with ethylacetate (EtOAc) and fractionated on a polyamide column with methanol as eluent produced five principal fractions. These fractions were designated as fraction A (74.8 mg yield and rich in alkaloids), fraction B (36.6 mg), fraction C (7.8 mg yield, monomeric procyanidin), fraction D (26.6 mg yield, rich in monomeric and oligomeric procyanidin), and fraction E (18.1 mg yield, rich in polymeric procyanidin). The original MeOH extract administered (100 mg/kg po) produced about 47% inhibition of carrageenin-induced paw oedema 1 h after administration. Fraction D, obtained from the ethylacetate extract and rich in procyanidins produced over 33% inhibition of carrageenan-induced paw oedema while a dose of 19.2 microg/ml produced 100% inhibitory effect on 5-lipoxygenase. A dose of 100 mg/kg of the MeOH extract also produced over 30% reduction of the sensitivity to pain while 50 mg/kg of fraction D rich in procyanidins produced over 45% analgesic effects. These results were judged significant compared to those obtained with indomethacin and acetylsalicylic acid. These findings suggest that extracts of the bark of Erythrophleum suaveolens possess potent anti-inflammatory and analgesic property and that the procyanidins lead to the observable pharmacological effects.

Anti-inflammatory and Analgesic Effects of Drypemolundein A, a Sesquiterpene Lactone from Drypetes molunduana

Previous pharmacological screening in our laboratory showed analgesic and anti-inflammatory effects of a crude stem bark extract of Drypetes molunduana. Phytochemical studies of this plant led to the isolation an structural elucidation of seven pentacylic triterpenes and one lignan, which were already known compounds, and a new furanosesquiterpene lactone, Drypemolundein A. The purpose of this study was to examine the anti-inflammatory and analgesic activities of drypemolundein A. The compound was studied against carrageenan-induced acute edema. At doses of 10 and 20 mg/kg, orally administered, it significantly reduced (57.57 and 66.66% inhibition at 1 h intervals, respectively) paw edema. At the same doses, this sesquiterpene lactone also exhibited significant analgesic action in force-induced pain in rat paw. These results indicate that drypemolundein A functions as an effective anti-inflammatory and analgesic agent.

Sesquiterpene lactone and friedelane derivative from Drypetes molunduana

A new sesquiterpene lactone, drypemolundein A and a new friedelane derivative, drypemolundein B, along with seven known compounds have been isolated from the whole stems of Drypetes molunduana Pax and Hoffm. Their structures were established on the basis of one- and two-dimensional NMR, homo- and hetero-nuclear spectroscopic evidence.

Isoprenylated flavonoids from the stem bark of Erythrina abyssinica

Three new prenylated flavanones, abyssinoflavanones V, VI, and VII (1-3), together with eight known flavanones (4-11) and two chalcones (12-13), were isolated from the stem bark of Erythrina abyssinica. Their structures were elucidated on the basis of spectroscopic and physicochemical analyses. All the isolates, with the exception of 1 and 8, strongly inhibited PTP1B activity in an in vitro assay with IC50 values ranging from 14.2 +/- 1.7 to 26.7 +/- 1.2 microM.

Effects of Alpinumisoflavone and Abyssinone V-4′-Methyl Ether Derived from Erythrina lysistemon (Fabaceae) on the Genital Tract of Ovariectomized Female Wistar Rat

Erythrina lysistemon is an African medicinal plant used as a palliative for problems in women. The crude extract of this plant was shown to exhibit estrogenic effects on the female rat reproductive tract and on cell cuture. Using classic chromatographic methods, two compounds have been isolated as major constituents of this extract: alpinumisoflavone (1) and abyssinone V‐4′‐methyl ether (2). To determine whether both compounds are actives principles accounting for E. lysistemon effects, we applied the classic 3‐day uterotrophic assay. We also carried out a ligand binding assay to determine whether the observed effects are estrogen receptor (ER) mediated. This study showed that whereas compound 1 displayed a fourfold preference for ERα, compound 2 bound ERα and ERβ with a same affinity. The in vivo study showed that compound 1 increased the uterine wet weight by 182.23% (pu2009<u20090.01) and 71.79% (pu2009<u20090.05) at doses of 0.1 and 1u2009mg/kg BW/day respectively. The uterine epithelium thickened dose‐dependently. Vaginal epithelial height also increased by 369.97 and 226.76% respectively (pu2009<u20090.01). Compound 2 acted only on the vagina and increased vaginal epithelial height by 244.56% (pu2009<u20090.01) at 1u2009mg/kg BW/day. These results suggest that compounds 1 and 2 are endowed with estrogenic properties accounting, at least in part, for E. lysistemon effects. Copyright

Isoflavonoids from Erythrina poeppigiana: evaluation of their binding affinity for the estrogen receptor.

Five new isoflavones, named 5,4-dihydroxy-7-methoxy-3-(3-methylbuten-2-yl)isoflavone (1), 5,2,4-trihydroxy-7-methoxy-5-(3-methylbuten-2-yl)isoflavone (2), 5,4-dihydroxy-7-methoxy-3-(3-methyl-2-hydroxybuten-3-yl)isoflavone (3), 3-formyl-5,4-dihydroxy-7-methoxyisoflavone (4), and 5-hydroxy-3-hydroxy-2,2-dimethyldihydropyrano[5,6:3,4]isoflavone (5), as well as six known compounds, wighteone (6), 3-isoprenylgenistein (7), isolupabigenin (8), alpinumisoflavone (9), erypoegin D (10), and crystacarpin (11), were isolated from Erythrina poeppigiana. The structures of the isolated compounds were elucidated on the basis of chemical and spectroscopic analysis. The affinity of these compounds for the estrogen receptors ERalpha and ERbeta was evaluated using a receptor binding assay. While isoprenyl and dimethylpyrano substituents in ring A reduced the affinity of binding to ERbeta ca. 100-fold compared to genistein, the isoprenyl substituent in ring B was better accommodated, allowing 7 to bind with ca. 10-fold lower affinity than genistein.

Waist circumference does not predict circulating adiponectin levels in sub-Saharan women

BackgroundBecause of previously reported ethnic differences in determinants and markers of obesity and related metabolic disorders, we sought to investigate circulating levels of adiponectin and their correlates in a sub-Saharan African (sSA) population.Subjects and MethodsWe studied 70 non-diabetic volunteers (33M/37F) living in Yaoundé, Cameroon, aged 24–69 yr, with BMI 20–42 kg/m2. In all participants we measured waist circumference and total body fat by bioimpedance, and obtained a fasting venous blood sample for measurement of plasma glucose, serum insulin and adiponectin concentrations. We performed a euglycaemic hyperinsulinaemic clamp in 1/4 subjects, and HOMAIR was used as surrogate of fasting insulin sensitivity index since it best correlates to clamp measurements.ResultsMales had lower adiponectin levels than females (8.8 ± 4.3 vs. 11.8 ± 5.5 μg/L). There was no significant correlation between adiponectin and total body fat (rs = -0.03; NS), whereas adiponectin was inversely correlated with waist circumference (rs = -0.39; p = 0.001). Adiponectin correlated negatively with insulin resistance (rs = -0.35; p = 0.01). In a regression analysis using fasting adiponectin concentration as the dependent variable, and age, HOMAIR, waist circumference, and fat mass as predictors, waist circumference (β = -3.30; p = 0.002), fat mass (β = -2.68; p = 0.01), and insulin resistance (β = -2.38; p = 0.02) but not age (β = 1.11; p = 0.27) were independent predictors of adiponectin. When considering gender, these relations persisted with the exception of waist circumference in females.ConclusionAdiponectin correlates in this study population are comparable to those observed in Caucasians with the exception of waist circumference in women. The metabolic significance of waist circumference is therefore questioned in sSA women.

Four new chalcones from Erythrina abyssinica.

Four new chalcones 1 - 4, named abyssinones A - D, were isolated from the stem bark of the plant Erythrina abyssinica and their structures were elucidated on the basis of spectroscopic analyses. The compounds 1, 3, and 4 were found to exhibit moderate cytotoxic activity against the human colorectal cancer cell line (Caco2) with IC (50) values of 13.3, 15.1, and 11.1 microM, respectively.

Phytotherapy and Womenʼs Reproductive Health: The Cameroonian Perspective

Approximately 80 % of the population in Africa use traditional medicinal plants to improve their state of health. The reason of such a wide use of medicinal plants has been mainly attributed to their accessibility and affordability. Expectation of little if any side effects, of a natural and therefore safe treatment regimen, as well as traditional beliefs additionally contribute to their popularity. Several of these plants are used by women to relieve problems related to their reproductive health, during or after their reproductive life, during pregnancy, or following parturition. The African pharmacopoeia thus provides plants used for preventing and/or treating gynecological infections, dysmenorrhea, irregular menstruations, oligomenorrhea or protracted menstruation, and infertility. Such plants may then be used as antimicrobians, emmenagogues, or as suppressors of uterine flow. African medicinal plants are also used during pregnancy for prenatal care, against fetal malposition or malpresentation, retained dead fetus, and against threatened abortion. Some others are used as anti-fertilizing drugs for birth control. Such plants may exert various activities, namely, anti-implantation or early abortifacient, anti-zygotic, blastocytotoxic, and anti-ovulatory effects. Some herbs could also act as sexual drive suppressors or as a post-coital contraceptive by reducing the fertility index. A number of these plants have already been subject to scientific investigations and many of their properties have been assessed as estrogenic, oxytocic, or anti-implantation. Taking into account the diversity of the African pharmacopoeia, we are still at an early stage in the phytochemical and pharmacological characterization of these medicinal plants that affect the female reproductive system, in order to determine, through in vitro and in vivo studies, their pharmacological properties and their active principles.