Maximilienne Nyegue

Profile and quantification of glucosinolates in Pentadiplandra brazzeana Baillon

Glucosinolates (GLs) present in root, seed, and leaf extracts of Pentadiplandra brazzeana Baillon were characterized and quantified according to the ISO 9167-1 method based on the HPLC analysis of desulfo-GLs. The analyses were complemented by GC-MS analyses of the isothiocyanates (ITCs) generated from GL degradation by myrosinase. Glucotropaeolin (1a), glucolimnanthin (2a), and glucoaubrietin (3a) were shown to be present in the root extract, whereas the seed mainly contained 3a. 3,4-Dimethoxybenzyl GL (4a), glucobrassicin (5a) and traces of 1a were detected in the leaf extract. The products were fully characterized as their desulfo-counterparts by spectroscopic techniques.

Characterization of Mexican Coriander (Eryngium foetidum) Essential Oil and Its Inactivation of Listeria monocytogenes In Vitro and during Mild Thermal Pasteurization of Pineapple Juice

The aim of this work was to characterize the essential oil (EO) of Eryngium foetidum (EfEO) and assess its activity toward Listeria monocytogenes in broth and during thermal inactivation of the pathogen in pineapple juice. In this respect, EfEO was chemically characterized, and its antilisteria potential in broth as a function of pH, cell load, and EfEO concentration was assessed through a central composite design. Furthermore, the inactivation kinetics of L. monocytogenes in the juice were assessed by combining EfEO and low pasteurization temperatures. A total of 81 compounds were identified from EfEO. The reduction of pH and cell load increased EO activity. The use of only 15 ppm of EfEO during pasteurization of pineapple juice at 60°C reduced the time required for a 4-log reduction in L. monocytogenes CFU/ml by 74.9% (i.e., from 8.5 to 2.1 min) compared with treatment without EfEO. It could be concluded that EfEO activity toward L. monocytogenes increases with the reduction of pH and that it can be used at sublethal concentrations in combination with low temperatures in pineapple juice pasteurization. This study demonstrates that EO-assisted pasteurization is a promising strategy for the reduction of thermal impact during juice production. EfEO is easily available and compatible with many juices and is thus promising for industrial application.

Stability of benzylic-type isothiocyanates in hydrodistillation-mimicking conditions.

Pentadiplandra brazzeana Baillon (Pentadiplandraceae) is known to contain benzyl-, 3-methoxybenzyl-, 4-methoxybenzyl-, 3,4-dimethoxybenzyl-, and indole-type glucosinolates, and the essential oil obtained from its roots is mainly constituted of benzyl isothiocyanate and benzyl cyanide. In a previous study by the authors, it was surmised that partial hydrolytic degradation of 4-methoxybenzyl isothiocyanate, one major expected compound, occurred during the hydrodistillation process of essential oil preparation. To probe this hypothesis, a selection of diversely substituted benzylic-type isothiocyanates was submitted to standard hydrodistillation-mimicking conditions. After extraction with dichloromethane, the reaction mixtures were analyzed using GC-MS. The aqueous phases resulting from liquid-liquid extraction were analyzed by HPLC and GC-MS. 2-Methoxybenzyl, 4-methoxybenzyl, 3,4-dimethoxybenzyl, and 3,4,5-trimethoxybenzyl isothiocyanates underwent conversion into 2-methoxybenzyl, 4-methoxybenzyl, 3,4-dimethoxybenzyl, and 3,4,5-trimethoxybenzyl alcohols, respectively, whereas benzyl, 3-methoxybenzyl, and 4-chlorobenzyl isothiocyanates were converted into the corresponding benzylamines.

Potent Natural Soluble Epoxide Hydrolase Inhibitors from Pentadiplandra brazzeana Baillon: Synthesis, Quantification, and Measurement of Biological Activities In Vitro and In Vivo

We describe here three urea-based soluble epoxide hydrolase (sEH) inhibitors from the root of the plant Pentadiplandra brazzeana. The concentration of these ureas in the root was quantified by LC-MS/MS, showing that 1, 3-bis (4-methoxybenzyl) urea (MMU) is the most abundant (42.3 μg/g dry root weight). All of the ureas were chemically synthesized, and their inhibitory activity toward recombinant human and recombinant rat sEH was measured. The most potent compound, MMU, showed an IC50 of 92 nM via fluorescent assay and a Ki of 54 nM via radioactivity-based assay on human sEH. MMU effectively reduced inflammatory pain in a rat nociceptive pain assay. These compounds are among the most potent sEH inhibitors derived from natural sources. Moreover, inhibition of sEH by these compounds may mechanistically explain some of the therapeutic effects of P. brazzeana.

Volatile components of fresh Pleurotus ostreatus and Termitomyces shimperi from Cameroon

Abstract Odorous wild Pleurotus ostreatus and Termitomyces shimperi from Cameroon are highly appreciated for both their culinary value and their good taste. The edible mushrooms were investigated for volatile constituents by GC-MS using organic solvent extraction. Twenty-eight and 24 volatile components were identified by solvent method for P. ostreatus and T. shimperi, respectively, and biosynthesized from the lipidic, shikimic and terpenic pathways. The major odorous compounds identified in fresh P. ostreatus organic extract were C8 components (mushroom odors) as octen-3-ol (59.3%), octen-3-one, octan-3-one, 3-octanol, n-octanal, (E)-2-octenal and n-octanol. Benzaldehyde (almond odor), benzyl alcohol (sweet-spicy odor) and phenylethanol (rose odor) as well as monoterpe-nes, i.e., linalool and linalool oxide detected from the Common Oyster Mushroom may also contribute to its pleasant flavour. Many aliphatic compounds dominate the volatile content of fresh T. shimperi, i.e., C6 derivatives (hexan-2-one, hexan-3-ol, hexanal, hexan-2-ol), C7 derivative (hept-2-enol) and C8 derivatives (octen-3-ol, 1-octen-3-one, octan-3-one, (E)-2-octenal). Within the aromatic components, phenylethanol was the main component identified from T. shimperi. Most of the volatiles identified from P. ostreatus and T. shimperi are widely used as aroma components in flavor industry due to their strong pleasant flavours.

Secondary metabolites from Triclisia gilletii (De Wild) Staner (Menispermaceae) with antimycobacterial activity against Mycobacterium tuberculosis

Abstract Triclisinone (2), a new ochnaflavone derivative, was isolated from the aerial parts of Triclisia gilletii, along with known drypemolundein B (1) and eight other known compounds. The chemical shifts of drypemolundein B (1) have been partially revised based on reinterpretation of NMR spectroscopic data. The eight other secondary metabolites are composed of: (+)-nonacosan-10-ol (3); stigmasterol (4), 3-O-β-D-glucopyranosylsitosterol (5), 3-O-β-D-glucopyranosylstigmasterol (6); oleanic acid (7); myricetin (8), quercetin (9) and 3-methoxyquercetin (10). Their structures were elucidated using IR, MS, NMR 1D and 2D, 1H and 13C and comparison with literature data. Furthermore, compounds 1, 2, 5, 6, 8, 9 and the crude extract were tested against Mycobacterium tuberculosis. Compounds 1, 2, 8 and 9 displayed moderate to very good activity against resistant strain (codified AC 45) of M. tuberculosis with minimum inhibitory concentrations MICs ranging from 3.90 to 62.5 μg/mL.

Chemical Composition, Antiradical and Antifungal Activities of Essential Oil of Fresh Leaves of Clerodendrum buchholzii (Gürke) from Cameroon

Abstract The Chemical composition of the essential oil obtained by hydrodistillation of fresh leaves of Clerodendrum buchholzii grown in Cameroon was investigated by GC and GC-MS. The major constituents were benzaldehyde (96%) and octen-3-ol which were also determined by AEDA method as the key odorants of the mixture. The antiradical screening tests indicates low scavenging activity against DPPH. Antifungal screening tests have been done on six fungal species (Candida albicans, Microsporum canis, Trichophyton rubrum, Fusarium moniliforme, Aspergillus flavus and Aspergillus niger). The results showed an important inhibition efficiency of essential oil against the tested fungal species which justifies the traditional use of Clerodendrum buchholzii leaves by the local populations and traditional healers.

In vitro evaluation of the antifungal activity of extracts of Baillonella toxisperma (Pierre), a Sapotaceae, on the growth of some human pathogenic yeasts

An ethnopharmacological survey concerning medicinal properties of Baillonella toxisperma (Pierre) was carried out by interview with the indigenous population of Dimako village situated in the East region of Cameroon. The result showed that the plant is implicated in the treatment of many infections among which is fungal infections. To confirm the antifungal property of B. toxisperma (Pierre), the barks and leaves of the plant were collected and serial extractions in water, hydro-ethanol mixture (3:7), ethanol, methanol and ethyl acetate were performed in vitro. One part of the hydro-ethanol (3:7) extract was degreased by mixing in water-hexane mixture (1:1). The extracts were then tested in vitro against Candida albicans, Candida parasilopsis, Candida sp. responsible for superficial, deep or systemic mycosis and against Cryptococcus neoformans responsible for sub-acute meningitis in immunodeficient individuals. The susceptibility of yeasts to plant extracts was evaluated using the wells diffusion method and yeasts growth inhibition parameters were evaluated according to the proposed National Committee for Clinical Laboratory Standards (NCCLS) M27-A2 standard guidelines (2002). The minimal inhibitory concentrations (MIC) and minimal fungicidal concentrations (MFC) determined were between 0.93 and 30.0 mg/ml. The extracts were fungicidal on clinical yeasts tested with MFC/MIC ratio of 1 or 2. The hexane phase HT2 from the hydro-ethanol crude extract of the barks gave the best antifungal activity on C. neoformans, with a MIC of 0.93 mg/ml and a MFC of 1.87 mg/ml. This activity was similar to the one obtained with fluconazole. Phytochemical screening revealed the presence of polyphenols, phenols, tannins, flavonoids, steroids, alkaloids, saponins, phlobatannins, triterpenes, anthocyanins, cardiac glycosides, leucoanthocyanins and fats, which are bioactive substances. The results could explain scientific validation to the traditional medical uses of B. toxisperma (Pierre) to treat fungal infections. Key words: Cameroon, Baillonella toxisperma (Pierre), ethnopharmacology survey, fungal infections, bioactive compounds.

Applying the hydrodistillation process to Pentadiplandra brazzeana Baill. root: a chemical assessment

Abstract A chemical study of the volatile components obtained by applying the hydrodistillation and reflux processes to Pentadiplandra brazzeana roots was performed by GC-FID and GC-MS. The hydrodistillation process showed a total yield of 0.97% with 0.11% of essential oil and 0.86% of volatile compounds from the aqueous reaction medium; in the reflux process, the volatile extract yield was 1.03%. Benzylic-type isothiocyanates were the major degradation products of glucosinolates in the essential oil (95.0%); the CH2Cl2 extracts obtained from the aqueous solutions were characterised by alcohols and amines in both processes. This study has shown that during hydrodistillation, only 10% of the glucosinolate degradation products are recovered in the essential oil whereas 90% remain in the aqueous medium, being converted into alcohols and amines. The relative percentages of the different chemical classes recovered in our experimental conditions are discussed in relation with the glucosinolate composition in the raw material.

Chemical Composition and in vitro Antibacterial Activity of the Essential Oils of the Leaves, Resin and Stem-Barks of Dacryodes edulis (G. Don) H. J Lam growing in Cameroon on Diarrhea Associated Strains

The aim of this work was to determine the chemical profile and assess in vitro the antibacterial activity of the leaves, resin and stem-barks of Dacryodes edulis. The essential oils were analyzed simultaneously by Gas Chromatography and Gas Chromatography coupled to Mass Spectrometry. Agar diffusion well and microdilution methods were used to assay the antibacterial activity. The resin essential oil contained p-cymene (30.32%), αthujene (28.58%), α-phellandrene (27.14%) and β-phellandrene (10.16%) as the main components; the stembarks essential oil had as abundant components p-cymene (35.14%), trans-carveol (22.60%), α-thujene (14.86%), β-phellandrene (8.65%) and β-elemene (5.22%). The leaves essential oil was distinct with elemol (29.22%), caryophyllene oxide (15.26%), trans-carveol (11.80%) and spathulenol (6.28%) as major components. The leaves essential oil was the most active with MIC and MBC value of 18.75 mg/mL on B. cereus; the most susceptible strain. The stem-barks essential oil had a MIC of 50 mg/mL and MBC of 100 mg/mL on all the strains meanwhile the resin essential oil had a bacteriostatic effect at 200 mg/mL. Based on these results, it emanates that the essential oils of D. edulis represent a potential source of antibacterial substances.