Nina Hermans

Correlation between chemical composition and antibacterial activity of essential oils of some aromatic medicinal plants growing in the Democratic Republic of Congo.

The chemical composition of essential oils from 15 aromatic medicinal plant species growing in the Democratic Republic of Congo have been studied. More than 15 constituents in an amount higher than 0.1% were identified in each essential oil. 1,8-cineole, alpha and beta-pinene, p-cymene, myrcene, gamma-terpinene, alpha-terpineol and limonene were prevalent constituents in almost more than 10 selected plant species. Results from the antibacterial testing by the diffusion method indicate that all essential oils (5 microl per disc) inhibited the growth of selected bacteria at different extents. The most active antibacterial essential oils were those of the leaves of Eucalyptus camadulensis and Eucalyptus terticornis (12-30 mm zone diameter of inhibition). They showed particularly a most potent inhibition of Pseudomonas aeruginosa growth (15-16 mm), followed by Eucalyptus robusta (12 mm). Essential oils from the leaves of Eucalyptus alba, Eucalyptus citriodora, Eucalyptus deglupta, Eucalyptus globulus, Eucalyptus saligna, Eucalyptus robusta, Aframomum stipulatum, Cymbopogon citratus, Ocimum americanum and that of the seeds of Monodora myristica showed also a good antibacterial activity (10-18 mm). Eucalyptus propinqua, Eucalyptus urophylla and Ocimum gratissimum essential oils were the less active samples against the selected bacteria. No correlation between the amount of major constituents such as 1,8-cineol, alpha-pinene, p-cymene, cryptone or thymol and the antibacterial activity was observed.

Proanthocyanidins in Health Care: Current and New Trends

Polyphenolic compounds are widely distributed in higher plants and are an integral part of the human diet. Recent interest in these substances has been stimulated by their potential health benefits, which are believed to arise mainly from their antioxidant activity. In the past years, the antioxidant activity of flavonoids has been studied in detail. An important but often overlooked group of polyphenols is that of the proanthocyanidins. Therefore, the present review is focused mainly on the antioxidant activity of proanthocyanidins and its relevancy in vivo. The three most important mechanisms of their antioxidant action will be discussed, i.e. free radical scavenging activity, chelation of transition metals, and inhibition of enzymes. In addition, the protective role of proanthocyanidins against lipid peroxidation and peroxynitrite, as well as their antimicrobial properties will be discussed. To study the in vivo relevancy of the proanthocyanidin activities, the knowledge of their pharmacokinetic parameters is crucial. Although bioavailability and metabolism data on polyphenols in general and proanthocyanidins in particular are still largely unavailable, the first reports indicate that at least monomers and smaller oligomeric procyanidins are absorbed. There is also considerable scientific and public interest in the important role that antioxidants may play in health care, e.g. by acting as cancer chemopreventive and anti-inflammatory agents and by reducing risk of cardiovascular mortality. Each of these aspects will be discussed, with special attention to the role of proanthocyanidins on apoptosis, gene expression and transcription factors, such as NF-kappa B.

In-vivo antimalarial activity of Cassia occidentalis, Morinda morindoides and Phyllanthus niruri.

The ethanolic, dichloromethane and lyophilized aqueous extracts of Cassia occidentalis root bark, Morinda morindoides leaves and whole plants of Phyllanthus niruri were evaluated for their antimalarial activity in vivo, in 4-day, suppressive assays against Plasmodium berghei ANKA in mice. No toxic effect or mortality was observed in mice treated, orally, with any of the extracts as a single dose, of 500 mg/kg body weight, or as the same dose given twice weekly for 4 weeks (to give a total dose of 4 g/kg). No significant lesions were observed, by eye or during histopathological examinations, in the hearts, lungs, spleens, kidneys, livers, large intestines or brains of any mouse. At doses of 200 mg/kg, all the ethanolic and dichloromethane extracts produced significant chemosuppressions of parasitaemia (of > 60% for C. occidentalis root bark and Ph. niruri whole plant, and of 30% for M. morindoides leaves) when administered orally. The most active ethanolic extract, that of Ph. niruri, reduced parasitaemia by 73%. The dichloromethane extracts of M. morindoides and Ph. niruri produced similar reductions (74% and 72% chemosuppression, respectively), whereas that of C. occidentalis was slightly less active (60% chemosuppression). Each lyophilized aqueous extract was less active than the corresponding ethanolic extract.

FURTHER EVALUATION OF RWANDAN MEDICINAL PLANT EXTRACTS FOR THEIR ANTIMICROBIAL AND ANTIVIRAL ACTIVITIES

A total of 45 Rwandan plant extracts, belonging to 37 different plant species out of 21 families, were investigated for their antibacterial, antifungal, and antiviral properties. The plants were selected on the base of their ethnomedicinal use against infections and autoimmune diseases. From all the plant extracts tested, only Clematis hirsuta (leaves) showed a pronounced antifungal activity against Candida albicans and the dermatophytes Trichophyton rubrum, Epidermophyton floccosum, and Microsporum canis. Seven plant extracts showed a high antiviral activity against the DNA-virus Herpes simplex type 1, while five and three plant extracts were highly active against the RNA-viruses Coxsackie and Polio, respectively. Only Macaranga kilimandscharica (leaves) showed an interesting anti-measles activity, whereas Eriosema montanum (leaves) and Entada abyssinica (leaves) were highly active against Semliki forest virus. Some plant extracts showed an antibacterial activity against Gram-positive bacteria and Mycobacterium fortuitum, but none of them were active against the Gram-negative bacteria tested.

Antiviral activity of Rwandan medicinal plants against human immunodeficiency virus type-1 (HIV-1)

Hawaiian medicinal plants commonly used for the treatment of a variety of infections were screened for antiviral activity against human immunodeficiency virus type 1 (HIV-1). Sixty-one extracts derived from seventeen plants were tested for selective viral growth inhibition using the LAI (HTLV-IIIB) isolate. The greatest degree of antiviral activity was observed with aqueous extracts made from the bark of Eugenia malaccensis (L.) and the leaves of Pluchea indica (Less.) which had antiviral selectivity indices (50% cytotoxic concentration/50% effective antiviral concentration) of 109 and 94, respectively. These and other extracts conferred 100% cell protection against viral cytopathic effect when compared with control samples. Methanol and water extracts made from the Pipturus albidus (Gray) leaves and bark also achieved a high selective inhibition of virus replication with very low cytotoxicity. Plant extracts made from Aleurites moluccana (Willd.), Psychotria hawaiiensis (Gray), Clermontia aborescens (Mann), and Scaevola sericea (Forst.) also showed antiviral activity. These data provide a rationale for the characterization of antiviral natural products from these plants and related plant species.

DPP4 inhibition improves functional outcome after renal ischemia-reperfusion injury

Dipeptidyl peptidase 4 (DPP4) is an exopeptidase which modulates the function of its substrates, among which are insulin-releasing incretins. DPP4 inhibitors are currently used to improve glucose tolerance in type 2 diabetes patients. Inhibition of DPP4 exhibits protective effects on ischemia-reperfusion injury (IRI) of the heart and lung. As DPP4 and its substrates are also expressed in the kidney, we studied the effect of the DPP4 inhibitor vildagliptin on the outcome of IRI-induced acute kidney injury in rats in a model of 30-min unilateral renal ischemia, followed by contralateral nephrectomy. Saline, 1, or 10 mg/kg vildagliptin (VG1/VG10) was administered intravenously 15 min before the surgery. Animals were euthanized after 2, 12, amd 48 h of reperfusion. DPP4 inhibition resulted in a significant dose-dependent decrease in serum creatinine (1.31 ± 0.32 and 0.70 ± 0.19 mg/dl for VG1 and VG10, respectively, vs. 1.91 ± 0.28 mg/dl for controls at 12 h; P < 0.01). Tubular morphology (PAS-PCNA) revealed significantly reduced tubular necrosis at 12 h (62.1 ± 18.0 and 77.5 ± 22.0% in VG10 and saline, respectively). VG did not affect regeneration but decreased apoptosis, as shown by twofold decreased Bax/Bcl-2 mRNA expression and a threefold decrease in apoptotic bodies on terminal deoxynucleotidyl transferase dUTP nick-end labeling-stained sections. VG treatment significantly reduced serum malondialdehyde twofold in both VG1- and VG10-treated ischemic and sham-operated animals compared with controls and also resulted in a significant decrease in mRNA expression of the proinflammatory marker CXCL10 at 2 h of reperfusion. Through a mechanism yet to be fully understood, VG treatment results in a functional protection of the kidney against IRI. This protection was associated with antiapoptotic, immunological, and antioxidative changes.

Radical scavenging and xanthine oxidase inhibitory activity of phenolic compounds from Bridelia ferruginea stem bark

Bridelia ferruginea Benth. (Euphorbiaceae) is a subtropical medicinal plant widely used in traditional African medicine against various diseases, including rheumatic pains. Seven of its constituents (3‐O‐methylquercetin (1), 3,7,3′,4′‐tetra‐O‐methylquercetin (rutisin, 2), myricetin (3), 3′,4′,5′‐tri‐O‐methylmyricetin (ferrugin, 4), 3,3′,4′,5′‐tetra‐O‐methylmyricetin (5), quercetin 3‐O‐glucoside (6), and a biflavanol gallocatechin‐[4′‐O‐7]‐epigallocatechin (7)) have been evaluated in‐vitro in the xanthine‐xanthine oxidase enzymatic system for inhibition of xanthine oxidase and radical scavenging activity. Results indicated that compounds 1, 3, 4 and 6 exhibited, at different levels, xanthine oxidase inhibiting and superoxide scavenging activity at micromolar concentrations, whereas compound 7 showed scavenging activity only. Compounds 2 and 5 were inactive in both cases. Study of the structure‐activity relationship demonstrated that for flavonoids the xanthine oxidase inhibitory activity was reduced by methylation of the hydroxyl functionality at C‐3 and in rings A and B. These results may partly explain and support the use of B. ferruginea stem bark for the treatment of rheumatic pains in traditional medicine.

Screening of Tanzanian medicinal plants against Plasmodium falciparum and human immunodeficiency virus.

Medicinal plants used to treat infectious diseases in Bunda district, Tanzania, were screened for activity against Plasmodium falciparum and Human Immunodeficiency Virus Type 1 (HIV-1, IIIB strain) and Type 2 (HIV-2, ROD strain). Antiplasmodial activity was observed for the 80 % MeOH extract of Ormocarpum kirkii (root; MIC = 31.25 microg/mL), Combretum adenogonium (leaves), Euphorbia tirucalli (root), Harrisonia abyssinica (root), Rhynchosia sublobata (root), Sesbania sesban (root), Tithonia diversifolia (leaves), and Vernonia cinerascens (leaves; MIC value of 62.5 microg/mL). With regard to HIV, 80 % MeOH extracts of Barleria eranthemoides (root), Combretum adenogonium (leaves and stem bark), Elaeodedron schlechteranum (stem bark and root bark), Lannea schweinfurthii (stem bark), Terminalia mollis (stem bark and root bark), Acacia tortilis (stem bark), Ficus cycamorus (stem bark) and Indigofera colutea (shoot), as well as H2O extracts from Barleria eranthemoides (root), Combretum adenogonium (leaves and stem bark), and Terminalia mollis (stem bark and root bark) exhibited IC50 values below 10 microg/mL against HIV-1 (IIIB strain). The highest anti-HIV-1 activity value was obtained for the B. eranthemoides 80 % MeOH root extract (IC50 value 2.1 microg/mL). Only a few extracts were active against HIV-2, such as the 80 % MeOH extract from Lannea schweinfurthii (stem bark) and Elaeodedron schlechteranum (root bark), showing IC50 values < 10 microg/mL.

Chemical Composition and Antifungal Activity of Essential Oils of Some Aromatic Medicinal Plants Growing in the Democratic Republic of Congo

Abstract The chemical composition and the antifungal activity of essential oils from 15 aromatic medicinal plant species growing in the Democratic Republic of Congo have been studied. More than 15 constituents in an amount ≥ 0.1% were identified in each oil. 1,8-Cineole, α- and β-pinene, P-cymene, α-terpineol, camphene and limonene were prevalent constituents. The antifungal activity of these oils (5 μL per disc) was evaluated by the diffusion method. Results indicate that all oils from fresh plant materials exhibited an antifungal activity at different levels against Candida albicans, Candida tropicalis, Aspergillus niger, Trichophyton mentagrophytes and Microsporum canis. A high antifungal activity was found in the leaf oil of E. tereticornis (15–22 mm) followed by the leaf oils of Eucalyptus alba (14–17 mm), E. camaldulensis, E. citriodora, E. globulus, Cymbopogon citratus and Monodora myristica seed oil (11–17 mm) against selected yeasts, fungus and dermatophytes. The leaf oils of E. deglupta, E. robusta, Ocimum gratissimum and Aframomum stipulatum also showed a good activity against selected microorganisms (10–12 mm). The less active oils were those from E. saligna, E. propinqua and O. americanum leaves. No correlation between the amount of some major constituents and the antifungal activity was observed.

Dietary silicon intake in Belgium: sources, availability from foods, and human serum levels.

The dietary intake of silicon by using the duplicate portion sampling technique of 24 hour-meals during 7 consecutive days is estimated.Since plant-based foods are major sources of silicon the elemental content is determined in various vegetarian foodstuffs commercially available in Belgium.Mean silicon intake from the 24-hour duplicate meals consumed daily by nearly 2000 persons was 18.6 +/- 8.5 mg/day. The major food sources were unrefined grains of high fibre content, cereal products and root vegetables. For vegetarian foods rice and barley revealed high silicon levels. Very high serum concentrations in newborns and concomittant low levels in the mothers indicated a homeostatic mechanism in humans. Besides the dietary intake, serum silicon levels of various population groups support the concept of essentiality of the element. An in vitro dialysability of the element in a simulated digestion procedure is used as a surrogate of silicon uptake.Silicon was readily available from foods but this correlated inversely with the elemental content.Serum silicon levels, as a function of age, gave indication of an important role of this element. In vitro availability study proved an inverse relation with the elemental content. A preliminary in vivo experiment confirmed that bioavailability is not only determined by concentration, but especially by the type of food and species under which silicon is present.