Phytochemical, Antiplasmodial, and Cytotoxic Investigation of Euclea natalensis A.DC. subsp. natalensis Leaves.

Previous research shows that the root and bark extracts of Euclea natalensis have antiplasmodial activity, but the leaves have not been examined yet. This study investigated the phytochemical, antiplasmodial, and cytotoxic properties of the plant leaves. The activity against 3D7 Plasmodium falciparum was determined using the parasite lactate dehydrogenase assay, and the cytotoxicity against Vero and HeLa cells was evaluated using the MTT and resazurin assays, respectively. The bioactive compounds were isolated by chromatography, and their structures were established with spectroscopic and spectrometric techniques. The extract showed antiplasmodial activity (IC50 =25.6 µg/mL) and was not cytotoxic against Vero cells (IC50 =403.7 µg/mL). Purification of the extract afforded six flavonoid glycosides, four triterpenoids, and a coumarin. The glycosides showed antiplasmodial and cytotoxic activities, against HeLa cells, at 50 µg/mL, but the activity was reduced at 10 µg/mL. Naphthoquinones, which are among the predominant phytochemicals in the root and root bark of E. natalensis, were not detected in the leaves.

Review of Ethnomedicinal Uses, Phytochemistry and Pharmacological Properties of Euclea natalensis A.DC.

Euclea natalensis is traditionally used as herbal medicine for several human diseases and ailments in tropical Africa. This study reviews information on ethnomedicinal uses, botany, phytochemical constituents, pharmacology and toxicity of E. natalensis. Results of this study are based on literature search from several sources including electronic databases, books, book chapters, websites, theses and conference proceedings. This study showed that E. natalensis is used as traditional medicine in 57.1% of the countries where it is indigenous. Euclea natalensis has a high degree of consensus on abdominal pains, antidote for snake bites, diabetes, diarrhoea, malaria, roundworms, stomach problems, toothache, venereal diseases and wounds. Several ethnopharmacological studies have shown that crude extracts and chemical compounds from E. natalensis demonstrated many biological activities both in vitro and in vivo, which included antibacterial, antidiabetic, antifungal, antimycobacterial, antiviral, antioxidant, antiplasmodial, larvicidal, antischistosomal, molluscicidal, dentin permeability and hepatoprotective activities. Future studies should focus on the mechanism of biological activities of both crude extracts and chemical compounds from the species, as well as structure-function relationships of bioactive constituents of the species.

Anticancer Properties and Pharmaceutical Applications of Plumbagin: A Review.

It has been shown that plumbagin, a bioactive naphthoquinone isolated from three major plant families viz. Plumbaginaceae, Ebenceae and Droseraceae, definitively exhibits anticancer potential in diverse cancer cells both in vitro and in vivo. Plumbagin shows antineoplastic effects via multi-channel molecular mechanisms, including the induction of apoptosis and autophagy, the disruption of the cell cycle, the inhibition of invasion and metastasis, and anti-angiogenesis. Plumbagin inhibits the growth of cancer cells mainly through the modulation of the signals of PI3K/Akt/mTOR, AMPK, Ras, and so on. The pharmaceutical applications of plumbagin combined with nanocarriers to achieve better therapeutic efficiency are discussed in this review Among them, liposomes, nanoparticles, microspheres, micelles, and nisosomes are used in cancer treatment. The anticancer study of plumbagin in vivo is also summarized in this review. On the whole, we aim to review the research progress of plumbagin both in pharmacological and pharmaceutical filed, which may provide some reference for further research of plumbagin.

Evaluation of the diuretic activity of the aqueous and 80% methanol extracts of the root of Euclea divinorum Hiern (Ebenaceae) in Sprague Dawley rats.

BACKGROUND: Diuretics are drugs that increase the formation of urine and are important for the treatment of various diseases including hypertension and edema. The root decoction of Euclea divinorum has been used as a diuretic agent in the traditional medicine. Therefore, this study was aimed to evaluate the diuretic activity of the crude extracts of the roots of Euclea divinorum in Sprague Dawley rats. METHODS: The aqueous extract (AE) and 80% methanol extract (80ME) of the plant were prepared using decoction and maceration, respectively. Vehicle (distilled water, 10ml/kg), standard drug (hydrochlorothiazide, 10mg/kg) and three doses (100mg/kg, 200mg/kg and 400mg/kg) of the AE and 80ME were given to male rats by oral gavage. Parameters like urine volume (for 5h), electrolyte concentration and pH were measured (at 5th h) and analyzed. Data were analyzed using one way analysis of variance (ANOVA) followed by Tukey post hoc test. Linear regression was also applied to show the dose dependency nature of the diuretic effect. RESULTS: The result indicated that the 80ME of the plant significantly (p<0.05) produced diuresis at 200mg/kg and 400mg/kg. Furthermore, the AE produced significant diuresis (p<0.05) at all doses. With regard to the electrolyte excretion, the AE produced significant natriuresis and kaliuresis at all tested doses (p<0.001), while the 80ME showed significant natriuresis and kaliuresis at 200mg/kg (p<0.01) and 400mg/kg (p<0.001). Preliminary phytochemical screening revealed the presence of secondary metabolites, including saponins, flavonoids, glycosides, steroids, tannins and terpinoids in both extracts. These constituents might be responsible for the diuretic activity of Euclea divinorum. Both extracts were also found to be safe at 2000mg/kg on the acute toxicity study. CONCLUSION: This finding provides a scientific support for the acclaimed traditional use of the roots of Euclea divinorum as a diuretic agent.

In vitro and In vivo antimycobacterial, hepatoprotective and immunomodulatory activity of Euclea natalensis and its mode of action.

ETHNOPHARMACOLOGICAL RELEVANCE: The Natal gwarri or Natal ebony (Euclea natalensis A.DC.) is a deciduous tree found widespread throughout southern Africa, especially in Kwazulu-Natal and the southern cost. It has been widely used by indigenous communities such as the Zulus, Tsongas and Vendas for symptoms related to tuberculosis (TB). The decoctions made from the plant parts are administered for chest diseases to treat complications such as chest pains, bronchitis, pleurisy and asthma. TB is prevalent in immune-compromised patients and it is evident that TB-drugs cause hepatotoxicity. The objective of the present study was therefore to evaluate the antimycobacterial activity of the ethanolic extract of E. natalensis against TB and its hepatoprotective and immunomodulatory activities. MATERIALS AND METHODS: The antimycobacterial, antioxidant, hepatoprotective, immunomodulatory activity and cytotoxicity of the ethanolic extract of the shoots of E. natalensis were determined in vitro. The mechanism of action of the antituberculosis activity was determined by investigating the inhibitory effect on mycothiol disulfide reductase enzyme. Furthermore, the acute, sub-acute toxicity (50-2000mg/kg) and antimycobacterial effect (300mg/kg) of E. natalensis shoot extract were investigated in Balb/c mice. Hepatoprotective activity of the extract (50-150mg/kg) was evaluated on isoniazid and rifampicin (50mg/kg; i.p.) induced hepatic damage in a rat model. RESULTS: The minimum inhibitory concentration of the extract was found to be 125µg/ml against Mycobacterium tuberculosis. The extracts 50% inhibitory concentration (IC50) against 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical was found to be 22.55µg/ml. The plant showed a hepatoprotective effect (50% at 12.5µg/ml) and the ability to increase T-helper 1 cell cytokines; Interleukin 12, Interleukin 2 and Interferon α by up to 12 fold and the ability to decrease the T-helper 2 cell cytokine Interleukin 10 4 fold when compared to baseline cytokine production. No cellular toxicity was observed in primary peripheral blood mononuclear cells (PBMC's) and two secondary cell lines; U937 monocytes and Chang liver cells (a derivative of the HepG2 cell line). During mechanistic studies, the extract showed a 50% inhibition of mycothiol reductase activity at 38.62µg/ml. During the acute and sub-acute studies, E. natalensis exhibited no toxic effect and the 50% lethal dose (LD50) was established to be above 2000mg/kg. The extract was able to reduce the mycobacterial load (1.5-fold reduction) in infected mice. Isoniazid and rifampicin caused significant hepatic damage in rats, and the extract was able to reduce the toxicity by 15% and 40% at 50 and 150mg/kg respectively. CONCLUSION: The present study supports the traditional usage of the plant against tuberculosis symptoms. The study showed the ability of E. natalensis shoot extract to inhibit mycobacterial growth, stimulate an appropriate immune response and have a hepatic protective effect. Due to the extract's significant results for hepatoprotective, immunomodulatory effects and antimycobacterial activity, it may prove to be effective to serve as an adjuvant for TB-patients.

Erosion and abrasion-inhibiting in situ effect of the Euclea natalensis plant of African regions.

This study evaluated the effect of Euclea natalensis gel on the reduction of erosive wear with or without abrasion, in enamel and dentin. During two five-day experimental crossover phases, volunteers (n = 10) wore palatal devices containing human enamel and dentin blocks (E = 8 and D = 8). The gel was applied in a thin layer in the experimental group, and was not applied in the control group. In the intraoral phase, volunteers used the palatal appliance for 12 h before the gel treatment, and were instructed to start the erosive challenges 6 h after the gel application. Erosion was performed with Coca-Cola® (for 5 min) 4 times/day. The appliance was then put back into the mouth and was brushed after 30 minutes. After intraoral exposure, the appliances were removed and the specimens were analyzed using profilometry (mean ± SD, µm). The Euclea natalensis gel caused less wear in enamel in the experimental group (EROS = 12.86 ± 1.75 µm; EROS + ABRAS = 12.13 ± 2.12 µm) than in the control group (EROS = 14.12 ± 7.66 µm; EROS + ABRAS = 16.29 ± 10.72 µm); however, the groups did not differ from each other significantly. A statistically significant value was found for erosion and eros + abrasion in dentin (p = 0.001). Euclea natalensis may play a role in the prevention of dentin loss under mild erosive and abrasive conditions. A clinical trial is required to confirm these promising results in a clinical situation.

Cytotoxic and immunomodulatory effects of Ebenus boissieri Barbey on breast cancer cells.

We aimed to determine the cytotoxic and immunomodulatory effects of hydroalcoholic extracts of the roots and aerial parts of Ebenus boissieri (EB) on breast cancer MDA-MB231 cells and the non-cancerous human embryonic kidney cell line, 293T. Cell viability was determined by MTT assay, trypan blue exclusion, and Live/Dead Viability/Cytotoxicity assay. Apoptosis was evaluated by measuring the activity of caspase-2, 3, 6, 8, and 9. Tumor necrosis factor (TNF)-α and interferon (IFN)-g release was assayed by ELISA, and protein expression of caspase-3, TNF-a, and IFN-g was determined by western blot. The results of this study revealed that MDA-MB231 cell viability was reduced in a dose-dependent manner by the aerial and root extract of EB at 72 h with a half-maximal inhibitory concentration (IC50) of 41.1 ± 2.76 and 65 ± 1.09 µg/mL, respectively. In contrast, neither the aerial nor the root extracts of this plant inhibited the proliferation of 293T cells at doses up to 1000 µg/mL. There was a time-dependent increase in caspase activity, especially caspase-3 and caspase-9. The levels of TNF-aand IFN-g significantly increased in MDA-MB231 cells treated with aerial extract. In conclusion, the extracts of EB induced apoptosis in breast cancer cells by altering the levels of caspases, TNF-a, and IFN-g. The components and precise modes of action of EB have not yet been determined. However, potential antitumor and immunomodulatory activity was observed along with selectivity against cancer cells in vitro, suggesting that hydroalcoholic extracts of this plant are worthy of additional study.

Aqueous extracts of Mozambican plants as alternative and environmentally safe acid-base indicators.

Indicators are substances that change color as the pH of the medium. Many of these substances are dyes of synthetic origin. The mulala plant (Euclea natalensis), which roots are commonly used by rural communities for their oral hygiene, and roseira (Hibiscus rosa-sinensis), an ornamental plant, are abundant in Mozambique. Currently, synthetic acid-base indicators are most commonly used but have environmental implications and, on the other hand, are expensive products, so the demand for natural indicators started. This study investigated the applicability of aqueous extracts of H. rosa-sinensis and E. natalensis as acid-base indicators. Ground on this work, the extracts can be used as acid-base indicators. On the basis of the absorption spectroscopy in both the UV-Vis region and previous studies, it was possible to preliminarily pinpoint anthocyanins and naphthoquinones as responsible for the shifting of colors depending on the pH range of aqueous extracts of H. rosa-sinensis and E. natalensis. These natural indicators are easily accessible, inexpensive, easy to extract, environmentally safe, and locally available.

Erosion and abrasion-inhibiting in situ effect of the Euclea natalensis plant of African regions

Abstract This study evaluated the effect of Euclea natalensis gel on the reduction of erosive wear with or without abrasion, in enamel and dentin. During two five-day experimental crossover phases, volunteers (n = 10) wore palatal devices containing human enamel and dentin blocks (E = 8 and D = 8). The gel was applied in a thin layer in the experimental group, and was not applied in the control group. In the intraoral phase, volunteers used the palatal appliance for 12 h before the gel treatment, and were instructed to start the erosive challenges 6 h after the gel application. Erosion was performed with Coca-Cola® (for 5 min) 4 times/day. The appliance was then put back into the mouth and was brushed after 30 minutes. After intraoral exposure, the appliances were removed and the specimens were analyzed using profilometry (mean ± SD, μm). The Euclea natalensis gel caused less wear in enamel in the experimental group (EROS = 12.86 ± 1.75 µm; EROS + ABRAS = 12.13 ± 2.12 µm) than in the control group (EROS = 14.12 ± 7.66 µm; EROS + ABRAS = 16.29 ± 10.72 µm); however, the groups did not differ from each other significantly. A statistically significant value was found for erosion and eros + abrasion in dentin (p = 0.001). Euclea natalensis may play a role in the prevention of dentin loss under mild erosive and abrasive conditions. A clinical trial is required to confirm these promising results in a clinical situation.

The tannosome is an organelle forming condensed tannins in the chlorophyllous organs of Tracheophyta.

BACKGROUND AND AIMS: Condensed tannins (also called proanthocyanidins) are widespread polymers of catechins and are essential for the defence mechanisms of vascular plants (Tracheophyta). A large body of evidence argues for the synthesis of monomeric epicatechin on the cytosolic face of the endoplasmic reticulum and its transport to the vacuole, although the site of its polymerization into tannins remains to be elucidated. The aim of the study was to re-examine the cellular frame of tannin polymerization in various representatives of the Tracheophyta. METHODS: Light microscopy epifluorescence, confocal microscopy, transmission electron microscopy (TEM), chemical analysis of tannins following cell fractionation, and immunocytochemistry were used as independent methods on tannin-rich samples from various organs from Cycadophyta, Ginkgophyta, Equisetophyta, Pteridophyta, Coniferophyta and Magnoliophyta. Tissues were fixed in a caffeine-glutaraldehyde mixture and examined by TEM. Other fresh samples were incubated with primary antibodies against proteins from both chloroplastic envelopes and a thylakoidal chlorophyll-carrying protein; they were also incubated with gelatin-Oregon Green, a fluorescent marker of condensed tannins. Coupled spectral analyses of chlorophyll and tannins were carried out by confocal microscopy on fresh tissues and tannin-rich accretions obtained through cell fractionation; chemical analyses of tannins and chlorophylls were also performed on the accretions. KEY RESULTS AND CONCLUSIONS: The presence of the three different chloroplast membranes inside vacuolar accretions that constitute the typical form of tannin storage in vascular plants was established in fresh tissues as well as in purified organelles, using several independent methods. Tannins are polymerized in a new chloroplast-derived organelle, the tannosome. These are formed by pearling of the thylakoids into 30 nm spheres, which are then encapsulated in a tannosome shuttle formed by budding from the chloroplast and bound by a membrane resulting from the fusion of both chloroplast envelopes. The shuttle conveys numerous tannosomes through the cytoplasm towards the vacuole in which it is then incorporated by invagination of the tonoplast. Finally, shuttles bound by a portion of tonoplast aggregate into tannin accretions which are stored in the vacuole. Polymerization of tannins occurs inside the tannosome regardless of the compartment being crossed. A complete sequence of events apparently valid in all studied Tracheophyta is described.

Eucleanal: a new napthalene derivative from Euclea divinorum.

A new naphthalene derivative, named eucleanal (1), was isolated from Euclea divinorum Hiern., and its structure elucidated by detailed spectroscopic (1H, 13C NMR, COSY, HMQC, HMBC) and HREIMS analysis.

Differential phenolic profiles in six African savanna woody species in relation to antiherbivore defense.

Low molecular weight phenolics are suggested to have a role in mediating diet selection in mammalian herbivores. However, very little is known about low molecular weight phenolic profiles of African savanna woody species. We determined low molecular weight phenolic profiles of six woody species with different life history, morphological and functional traits. We investigated interspecific phytochemical variation between species and found that: (1) related Acacia species were chemically dissimilar; (2) similarity percentage analysis revealed that Acacia grandicornuta was most dissimilar from other species and that the evergreen and unpalatable Euclea divinorum had a qualitatively similar chemical profile to the deciduous and palatable Acacia exuvialis and Combretum apiculatum; (3) C. apiculatum had the highest chemical diversity; (4) relative to spineless plants, spinescent plants contained significantly less HPLC phenolics and condensed tannins; and (5) the major quantitative difference between the evergreen and unpalatable E. divinorum and other species was its high myricitrin concentration.

Hypoglycemic evaluation of a new triterpene and other compounds isolated from Euclea undulata Thunb. var. myrtina (Ebenaceae) root bark.

AIM OF THE STUDY: Investigate the hypoglycaemic activity of the four isolated compounds from a crude acetone extract of the root bark of Euclea undulata var. myrtina, which is used by traditional healers in the Venda area, Limpopo Province in the treatment of diabetes. MATERIAL AND METHODS: The hypoglycaemic activity of the four compounds isolated from Euclea undulata was determined by in vitro screening of glucose utilization by C2C12 myocytes at a concentration of 25 µg/ml or 50 µg/ml. The inhibition of α-glucosidase was also tested at concentrations ranging from 0.02 to 200.00 µg/ml. RESULTS: Assay-guided isolation of the crude acetone extract of the root bark of Euclea undulata var. myrtina afforded a new triterpene, α-amyrin-3O-ß-(5-hydroxy) ferulic acid (1), in addition to three known compounds; betulin (2), lupeol (3) and epicatechin (4). The in vitro results on C2C12 myocytes suggest that compound 4 may have some effect to lowers blood glucose levels, whereas compound 1 has the ability to inhibit α-glucosidase at a concentration of 200.0 µg/ml with an IC50 value of 4.79 that correlates with that of the positive control acarbose IC50 value 4.75. CONCLUSION: The results suggest that 4 may have some ability to lower blood glucose levels, whereas 1 has the ability to inhibit α-glucosidase. ETHNOPHARMACOLOGICAL RELEVANCE: These findings corroborate the ethnomedicinal use of Euclea undulata by traditional healers for the treatment of diabetes as two substances was isolated from the acetone plant extract that exhibit hypoglycaemic activity.

Avaliação in situ do efeito do gel contendo euclea natalensis na superfície dentária, antes do desafio erosivo seguido ou não da abrasão / Evaluation in situ of the gel containing natalensis euclea effect on the tooth surface before the erosive challenge with or without abrasion

Este estudo avaliou in situ a ação do gel contendo euclea natalensis na redução da erosão associada ou não abrasão em esmalte e dentina humanos. O estudo foi realizado em duas fases cruzadas de cinco dias cada (SG - sem gel e CG - com gel) nas quais 10 voluntários utilizaram placas palatinas com 4 blocos de esmalte e 4 blocos de dentina, distribuídos em duas fileiras horizontais contendo 4 blocos, correspondendo aos subgrupos: erosão (Eros); erosão + abrasão (30min) (Eros + Abras). Em fases alternadas metade dos voluntários teve a aplicação do gel em todos espécimes do aparelho e na outra metade os espécimes não sofreram tratamento nenhum. O gel foi aplicado durante 5 minutos, sendo o mesmo removido após este tempo. Na etapa experimental os aparelhos foram imersos em refrigerante 4x ao dia, por 5 minutos. A seguir o aparelho foi colocado na boca por 30 minutos. Após este período os voluntários escovaram 4 espécimes da fileira Eros + Abras e recolocaram o aparelho. A outra fileira (Eros) não foi escovada. A análise da perda de estrutura dentária foi realizada por meio de teste de perfilometria e microdureza. Foi utilizada a análise de variância (ANOVA) a 2 critérios (presença ou ausência da aplicação do gel) de acordo com cada substrato e o teste TUCKEY (p<0,05). Não houve associação entre perda de dureza e condições ou grupos testados (p>0,05). O desgaste dentário médio nos blocos de esmalte para o grupo CG foi de 12,86µm eros e 12,13µm eros+abras e para os blocos de dentina foi de 5,95µm eros e 6,16µm eros+abras. A média de desgaste dentário para o grupo SG, em blocos de esmalte foi de 14,08µm eros e 16,29µm eros+abras e, nos blocos de dentina foi de 13,64µm eros e 12,63µm eros+abras. Houve diferença significativa entre os grupos (p<0,05). Concluiu-se que o gel contendo euclea natalensis é capaz de reduzir o desgaste associado ou não a abrasão, independente do tipo de substrato, esmalte ou dentina.

This study investigated the action of in situ gel containing euclea natalensis on reducing erosion associated or not with abrasion in the human enamel and dentin. The study was performed into two phases crossed in five days each (WOG-without gel and WG- with gel) in which ten volunteers used acrylic palatal appliances with four blocks of enamel and four dentin, distributed in two horizontal rows containing four blocks, corresponding to the subgroups: erosion (Eros); erosion + abrasion (30min) (Eros + Abras). In alternating phases half the volunteers had the applying the gel at all specimens. And the other half of the volunteers have not suffered any treatment. The gel was applied during 5 minutes, being removed after this time. In stage experimental, the blocks were subjected to erosion by immersion of the appliances into soft drink for five minutes, 4 times a day. The appliance was then replaced into the mouth for 30 minutes. After this period the volunteers brushed row (eros+abrasion) and replaced into the mouth. The row (eros) was not brushed. The analysis of the dental structure were determined using profilometry and microhardness tests. ANOVA by two criteria (presence or absence of application of gel) in agreement with each the substrate and Tukey test were applied (p <0.05). Microhardness and conditions or groups tested were not found association (p> 0.05). The mean wear in enamel blocks was 12.86µm eros and 12.13µm eros + abras in the WG group and in dentin blocks was 5.95 µm eros and 6.16µm eros+ abras. The mean wear in enamel blocks was 14.08µm eros and 16.29µm eros+abras for the WOG group and in dentin blocks was 13.64µm eros and 12.63µm eros + abras. There was significant difference between groups (p <0.05). It concluded that the gel containing Euclea Natalensis can reduce erosion with or without abrasion, independently of the substrate type, enamel or dentin.

Purified compounds and extracts from Euclea species with antimycobacterial activity against Mycobacterium bovis and fast-growing mycobacteria.

Naphthoquinones and other compounds with antimycobacterial activity against Mycobacterium tuberculosis have previously been isolated from Euclea species. In this study, several constituents of Euclea natalensis and E. undulata, as well as organic extracts of the leaves, were assessed for efficacy against the zoonotic pathogen, Mycobacterium bovis. Also included in the battery of test organisms were M. bovis BCG and the fast-growing species M. smegmatis and M. fortuitum. The acetone extract of E. natalensis had potent activity against M. bovis (MIC=26 microg/ml). The naphthoquinone 7-methyljuglone was the most active compound, with an MIC as low as 1.55 microg/ml against pathogenic M. bovis. M. bovis BCG was not as susceptible to the test compounds as the pathogenic strain, but similar patterns of activity were observed between all the strains tested. M. smegmatis appeared to be a better predictor of antimycobacterial activity against pathogenic M. bovis (and M. tuberculosis), while MIC values obtained using M. fortuitum correlated well with those of M. bovis BCG.

Assessment of the content of phenolics and antioxidant actions of the Rubiaceae, Ebenaceae, Celastraceae, Erythroxylaceae and Sterculaceae families of Mauritian endemic plants.

There is continued interest in the assessment of the bioefficacy of the active principles in extracts from a variety of traditional medicine and food plants in order to determine their impact on the management of a variety of clinical conditions and maintenance of health. The polyphenolic composition and antioxidant potential of Mauritian endemic plants of the Rubiaceae, Ebenaceae, Celastraceae, Erythroxylaceae and Sterculaceae family were determined. The phenolics level of the plant extracts varied from 1 to 75 mg/g FW, the maximum level measured in Diospyros neraudii (Ebenaceae). Coffea macrocarpa showed the highest flavonoids content with 18+/-0.7 mg/g FW. The antioxidant capacity based on the TEAC and FRAP values were strongly related to total phenolics and proanthocyanidins content, while a weaker correlation was observed with (-) gallic acid. Erythroxylum sideroxyloides showed the highest protective effect in the lipid peroxidation systems with IC(50) of 0.0435+/-0.001 mg FW/ml in the Fe(3+)/ascorbate system and 0.05+/-0.002 mg FW/ml in the AAPH system. Cassine orientalis, E. sideroxyloides, Diospyros mellanida and Chassalia coriancea var. johnstonii were weakly prooxidant only at higher concentration greater of 10 g FW/L indicating potential safety. Mauritian endemic plants, particularly the genus Diospyros, are good sources of phenolic antioxidants and potential candidates for the development of prophylactic agents.

Activity of 7-methyljuglone derivatives against Mycobacterium tuberculosis and as subversive substrates for mycothiol disulfide reductase.

The naphthoquinone 7-methyljuglone (5-hydroxy-7-methyl-1,4-naphthoquinone) has previously been isolated and identified as an active component of root extracts of Euclea natalensis which displays antitubercular activity. Herein, a series of synthetic and plant-derived naphthoquinone derivates of the 7-methyljuglone scaffold have been prepared and evaluated for antibacterial activity against Mycobacterium tuberculosis. Several of these compounds have been shown to operate as subversive substrates with mycothiol disulfide reductase. The absence of a direct correlation between antitubercular activity and subversive substrate efficiency with mycothiol disulfide reductase, might be a consequence of their non-specific reactivity with multiple biological targets (e.g. other disulfide reductases).

Activity of 7-methyljuglone in combination with antituberculous drugs against Mycobacterium tuberculosis.

The recent increase in the incidence of tuberculosis with the emergence of multidrug-resistant (MDR) cases has lead to the search for new drugs that are effective against MDR strains of Mycobacterium tuberculosis and can augment the potential of existing drugs against tuberculosis. In the present study, we investigated the activities of a naphthoquinone, 7-methyljuglone, isolated from the roots of Euclea natalensis alone and in combination with other antituberculous drugs against extracellular and intracellular M. tuberculosis. Combinations of 7-methyljuglone with isoniazid or rifampicin resulted in a four to six-fold reduction in the minimum inhibitory concentration of each compound. Fractional inhibitory concentration (FIC) indexes obtained were 0.2 and 0.5, respectively, for rifampicin and isoniazid, suggesting a synergistic interaction between 7-methyljuglone and these anti-TB drugs. The ability of 7-methyljuglone to enhance the activity of isoniazid and rifampicin against both extracellular and intracellular organisms suggests that 7-methyljuglone may serve as a promising compound for development as an anti-tuberculous agent.

Effects of two medicinal plants Psidium guajava L. (Myrtaceae) and Diospyros mespiliformis L. (Ebenaceae) leaf extracts on rat skeletal muscle cells in primary culture.

Crude decoction, aqueous and ethanolic extracts of two medicinal plants (Psidium guajava and Diospyros mespiliformis), widely used in the central plateau of Burkina Faso to treat many diseases were evaluated for their antagonistic effects on caffeine induced calcium release from sarcoplasmic reticulum of rat skeletal muscle cells. These different extracts showed a decrease of caffeine induced calcium release in a dose dependent manner. Comparison of the results showed that Psidium guajava leaf extracts are more active than extracts of Diospyros mespiliformis and that crude decoctions show better inhibitory activity. The observed results could explain their use as antihypertensive and antidiarrhoeal agents in traditional medicine, by inhibiting intracellular calcium release.

In vitro 12(S)-HETE inhibitory activities of naphthoquinones isolated from the root bark of Euclea racemosa ssp. schimperi.

Platelet 12-lipoxygenase is believed to play a role in cancer and other pathological conditions, such as psoriasis, atherosclerosis and arthritis. The inhibition of 12-LOX is a potential therapeutic approach in the treatment of tumor metastasis. The extracts of Euclea racemosa Murr. ssp. schimperi (A. DC.) F. White (Ebenaceae) obtained by maceration and naphthoquinones isolated from the dichloromethane extract have been investigated for their 12(S)-HETE inhibitory activity using human platelets. At 100 microg/ml, the dichloromethane extract inhibited the formation of 12(S)-HETE by 88.7% and compounds 7-methyljuglone (2), isodiospyrin (3), neodiospyrin (4) and mamegakinone (5), isolated from this extract, exhibited significant activities with IC(50) values ranging from 4 to 58 microg/ml (22.2-155.7 microM). Of these the most abundant compound, 7-methyljuglone displayed a potent inhibitory activity with an IC(50) value of 4.18 microg/ml (22.2 microM), which was comparable to the positive control baicalein with an IC(50) value of 5 microg/ml (18.5 microM). In contrast, 4(S)-shinanolone (1), the reduced form of compound 2, did not show any significant inhibitory activity even at a concentration of 60 microg/ml.