Antioxidant, antiglycation and cytotoxicity evaluation of selected medicinal plants of the Mascarene Islands.

BACKGROUND: Many indigenous plants of Mascarene Islands have been used in folkloric medicine to manage diabetes but few species have received scientific attention. Selected traditional medicinal plants (Antidesma madagascariense Lam. -Euphorbiaceae (AM), Erythroxylum macrocarpum O.E.Schulz -Erythroxylaceae (EM), Pittosporum senacia Putterl -Pittosporaceae (PS), Faujasiopsis flexuosa Lam. C.Jeffrey -Asteraceae (FF), Momordica charantia Linn -Cucurbitaceae (MC) and Ocimum tenuiflorum L -Lamiaceae (OT) were evaluated for their antioxidant, antiglycation and cytotoxic potential in vitro. METHODS: Graded concentrations (1.25-100 µg/mL) of the crude methanolic and water extracts and fractions (dichloromethane, ethyl-acetate, n-butanol and water) were evaluated for abilities to scavenge 2,2-diphenyl-2-picrylhydrazyl hydrate (DPPH), nitric oxide (NO), superoxide (SO) radicals and to inhibit lipoxygenase and formation of advanced glycation endproduct (AGE) in vitro. The MTT (3-(4, 5-dimethylthazol-2-yl)-2,5-diphenyl tetrazonium bromide) cytotoxicity test was performed on 3T3 cell line. RESULTS: Only IC50 for DPPH, SO, NO and lipoxygenase for AM, FF and OT crude extracts and fractions were comparable to ascorbic acid and quercetin activity. Crude aqueous extracts of AM and FF showed IC50 of 4.08 and 3.89 µg/mL respectively for lipoxygenase which was significantly lower (p < 0.05) than quercetin (10.86 ± 0.68 µg/mL). The three crude aqueous extracts of these plants and their n-butanol fractions also showed antiglycation activities (p < 0.05) comparable to aminoguanidine. Increasing concentrations (250-2000 µg/mL) of the six crude extracts (Methanol and water) and their fractions did not inhibit mitochondrial respiration as measured by MTT cytotoxicity assay. CONCLUSION: AM, FF and OT crude extracts and fractions have potent antioxidant and antiglycation properties with no apparent cytotoxicity and might have prophylactic and therapeutic potentials in the management of diabetes and related complications. Our study tends to validate the traditional use of these medicinal herbs and food plants as complementary and alternative medicines.

In vitro modulation of oxidative burst via release of reactive oxygen species from immune cells by extracts of selected tropical medicinal herbs and food plants.

OBJECTIVE: To evaluate in vitro immunomodulating properties and potential cytotoxicity of six tropical medicinal herbs and food plants namely Antidesma madagascariense (Euphorbiaceae) (AM), Erythroxylum macrocarpum (Erythroxylaceae) (EM), Faujasiopsis flexuosa (Asteraceae) (FF), Pittosporum senacia (Pittosporaceae) (PS), Momordica charantia (Cucurbitaceae) (MC) and Ocimum tenuiflorum (Lamiaceae) (OT). METHODS: Initially, the crude water and methanol extracts were probed for their capacity to trigger immune cells' NADPH oxidase and MPO-dependent activities as measured by lucigenin- and luminol-amplified chemiluminescence, respectively; as compared to receptor-dependent (serum opsonised zymosan- OPZ) or receptor-independent phorbol myristerate acetate (PMA). RESULTS: Preliminary screening on whole human blood oxidative burst activity showed significant and concentration-dependent immunomodulating properties of three plants AM, FF and OT. Further investigations of the fractions on isolated human polymorphonuclear cells (PMNs) and mice monocytes using two different pathways for activation of phagocytic oxidative burst showed that ethyl acetate fraction was the most potent extract. None of the active samples had cell-death effects on human PMNs, under the assay conditions as determined by the trypan-blue exclusion assay. Since PMA and OPZ NADPH oxidase complex is activated via different transduction pathways, these results suggest that AM, FF and OT does not affect a specific transductional pathway, but rather directly inhibit a final common biochemical target such as the NADPH oxidase enzyme and/or scavenges ROS. CONCLUSIONS: Our findings suggest that some of these plants extracts/fractions were able to modulate significantly immune response of phagocytes and monocytes at different steps, emphasizing their potential as a source of new natural alternative immunomodulatory agents.

Promoting African Medicinal Plants through an African Herbal Pharmacopoeia

Various resolutions adopted by the World Health Assembly and Regional Committee for Africa call upon Member States; among others things; to develop herbal pharmacopoeias and to develop and apply scientific criteria and methods for proof of safety and efficacy of medicinal plant products. However; only few countries have developed national herbal pharmacopoeias; limited plant species that provide medicinal herbs have been scientifically evaluated for their possible medical applications; and the safety and efficacy data are available for even fewer herbs. Without well documented information on the safety; efficacy and phytochemical characteristics of different compounds; it is difficult for external buyers to assess the likely utility or value of some new raw materials and extracts of African origin. In order to address these lacunae; the Association of African Medicinal Plants Standards is developing an African Herbal Pharmacopeia with trading standards which provide information and technical data on some 50 important medicinal plants. The objective of developing the monographs is to ensure that these plants become visible on the world market. The monographs lay emphasis on the quality control issues; dosage; use; efficacy; pharmacology and safety of important Africanmedicinal plants

In vitro and in vivo activity of Aloe vera leaf exudate in experimental visceral leishmaniasis.

The leishmanicidal activity of Aloe vera leaf exudate (AVL) has been demonstrated in promastigotes and axenic amastigotes, but its effectiveness in animal models has not been evaluated. The presence of alkaloids, triterpenes, cyanidines, proanthocyanidines, tannins, and saponins in AVL was identified. Its effectiveness in four Leishmania donovani strains was studied both in promastigotes (IC50 ranged from 70-115 microg/ml) and amastigotes (IC50 ranged from 3.1-11.4 microg/ml). In amastigotes, the killing by AVL was facilitated through its induction of nitric oxide in leishmania-infected macrophages. The safety index was good as AVL up to 300 microg/ml remained non-toxic to monocytes and macrophages. In a L. donovani BALB/c mouse model, oral or subcutaneous administration of AVL (15 mg/kg body weight x 5 days) reduced parasitemia by >90% in the liver, spleen, and bone marrow without impairment of hepatic and renal functions. Collectively, we conclude that AVL shows promising antileishmanial activity and may provide a new lead agent in the treatment of Leishmaniasis.

Screening for anti-infective properties of several medicinal plants of the Mauritians flora.

Several plants of the Mauritian flora alleged to possess anti-infective properties were studied against different strains of pathogenic bacteria and fungi. The grounded dried plant materials were extracted with different extractants and screened for anti-microbial activity using the disk diffusion and the micro-dilution techniques. Preliminary screening revealed that the methanol extracts were most active. Salmonella enteritidis, Enterobacter cloacae and Bacillus subtilis were the three test organisms, which were found to be susceptible to all the crude methanolic extracts of the different plants investigated (100% susceptibility), followed by Escherichia coli (57.1%) and Pseudomonas aeruginosa (57.1%), and Staphylococcus aureus (28.6%). The lowest minimum inhibitory concentration recorded for the different crude methanol extracts against Staphylococcus aureus, Escherichia coli, Salmonella enteritidis, Enterobacter cloacae, Bacillus subtilis and the mould fungus Candida albicans were 500, 1000, 125, 250, 1000 and 125 micro g/ml, respectively. Bioautography using Cladosporium cucumerinum revealed that dichloromethane (DCM) extracts had the highest activity against the phytopathogenic fungus. It was also noted that the DCM extracts of Michelia champaca and Antidesma madagascariense yielded the maximum number of growth inhibiting compounds against Cladosporium cucumerinum. Activity of the different crude extracts was also investigated against several phytopathogenic filamentous fungi, Colletotrichum glocosporoides, Rhizoctonia solani, Sclerotinia sclerotium, Guignardia sp. and Fusarium oxysporum. It was found that crude hexane extracts as well as crude DCM extracts exhibited marked activity against several strains of fungi, especially Colletotrichum glocosporoides, Sclerotinia sclerotium and Guignardia sp.

Constituents of Psiadia terebinthina A.J. Scott, an endemic Asteraceae from Mauritius.

Kaemferol-3-methyl ether (1), quercetin-3-methyl ether (2), kaemferol-3,7-dimethyl ether (3), 3-caffeoyl quinic acid (4) and 3,4-O-dicaffeoyl quinic acid (5) have been isolated for the first time from the leaves of Psiadia terebinthina A.J. Scott (Asteraceae). The identity of the compounds 1-5 were confirmed by various spectroscopic methods.

Medicinal plants: traditions of yesterday and drugs of tomorrow.

Plants have provided Man with all his needs in terms of shelter, clothing, food, flavours and fragrances as not the least, medicines. Plants have formed the basis of sophisticated traditional medicine systems among which are Ayurvedic, Unani, Chinese amongst others. These systems of medicine have given rise to some important drugs still in use today. Among the lesser-known systems of medicines are the African and Australian, Central and South American amongst others. The search for new molecules, nowadays, has taken a slightly different route where the science of ethnobotany and ethnopharmacognosy are being used as guide to lead the chemist towards different sources and classes of compounds. It is in this context that the flora of the tropics by virtue of its diversity has a significant role to play in being able to provide new leads. Nonetheless the issue of sovereignty and property rights should also be addressed in line with the Convention for Biological Diversity (CBD). This paper highlights the above, provides an overview of the classes of molecules present in plants and gives some examples of the types of molecules and secondary metabolites that have led to the development of these pharmacologically active extracts. The paper also presents some data on the use of plant products in the development of functional foods, addresses the needs for validation of plant extracts and always stressing on safety, efficacy and quality of phyto-medications.

Experimental evidence for in vitro fluid transport in the presence of a traditional medicinal fruit extract across rat everted intestinal sacs.

The present study was designed to investigate the effects of aqueous fruit extract of Momordica charantia (MC), a traditional medicinal plant, on the transport of fluid in vitro. Everted intestinal sacs from rats were mounted in an organ bath containing Krebs solution. We compared the effect of MC extract on water transport with increasing inorganic phosphate concentration with or without D-glucose in the buffer. In the control experiments, fluid uptake was enhanced significantly (P < 0.05) at high inorganic phosphate concentration (8-10 mM) in the presence of 5.5 mM D-glucose. Addition of 3.0 mg/mL MC extract to the serosal side inhibits the uptake of fluid significantly (P < 0.05). At high inorganic phosphate concentration (8-10 mM), fluid uptake was not inhibited (P > 0.05) when incubated with 3.0 mg/mL MC fruit extract. It is hypothesized that an increase in inorganic phosphate enhances oxidative phosphorylation thereby increasing the fluid uptake across everted intestinal sacs of rat. These findings seem to indicate that the MC-induced reduction on intestinal fluid absorption capacity could be mainly the result of an interference with the carrier-mediated coupled entrance of glucose and Na(+) across the brush-border membrane.

Chemical composition and in vitro antimicrobial activities of the essential oils from endemic Psiadia species growing in mauritius.

The composition of the leaf oils, obtained by hydrodistillation, of five endemic Psiadia species of the Asteraceae family were studied by GC/MS on both polar and non-polar columns. The analysis showed that the volatile components of the oils were made up essentially of monoterpenes, sesquiterpenes, aliphatics and other shikimic acid derivatives. With respect to the non-volatile components, great variations were observed: P. lithospermifolia contained (E)-isoasarone (51.5%); P. penninervia: eugenol (5.1%); P. terebinthina: eugenyl-acetate (4.0%); P. viscosa: pentyl-4-(1-methylethyl benzoate) (25.8%); P. arguta: isoeugenol (56.5%). In vitro antimicrobial assays using the agar-well diffusion method, revealed that most of the oils were not very active against the tested microorganisms except for that of P. lithospermifolia, which significantly inhibited the growth of Bacillus cereus, Staphylococcus aureus and Pseudomonas aureofaciens, Aspergillus ochraceus, Candida pseudotropicalis, Kluyveromyces lactis and Fusarium moniliforme. This activity has been attributed to the presence of delta-elemene, (E)-farnesene, alpha-curcumene, selina-4,7(11)-diene, (E,Z)-alpha-farnesene, beta-bisabolene some of which have established antimicrobial profiles. Likewise, the fungi toxic action of the oil of P. arguta against Aspergillus ochraceus, Candida pseudotropicalis, and Fusarium moniliforme, may be attributed to the presence of isoeugenol, eugenol being known to be mycotoxic especially against Aspergillus species.