Trypanocidal effects of gallic acid and related compounds

Antiprotozoal Activity of Plants Used in the Management of Sleeping Sickness in Angola and Bioactivity-Guided Fractionation of Brasenia schreberi J.F.Gmel and Nymphaea lotus L. Active against T. b. rhodesiense

Folk medicine is widely used in Angola, even for human African trypanosomiasis (sleeping sickness) in spite of the fact that the reference treatment is available for free. Aiming to validate herbal remedies in use, we selected nine medicinal plants and assessed their antitrypanosomal activity. A total of 122 extracts were prepared using different plant parts and solvents. A total of 15 extracts from seven different plants exhibited in vitro activity (>70% at 20 µg/mL) against Trypanosoma brucei rhodesiense bloodstream forms. The dichloromethane extract of Nymphaea lotus (leaves and leaflets) and the ethanolic extract of Brasenia schreberi (leaves) had IC50 values ≤ 10 µg/mL. These two aquatic plants are of particular interest. They are being co-applied in the form of a decoction of leaves because they are considered by local healers as male and female of the same species, the ethnotaxon "longa dia simbi". Bioassay-guided fractionation led to the identification of eight active molecules: gallic acid (IC50 0.5 µg/mL), methyl gallate (IC50 1.1 µg/mL), 2,3,4,6-tetragalloyl-glucopyranoside, ethyl gallate (IC50 0.5 µg/mL), 1,2,3,4,6-pentagalloyl-β-glucopyranoside (IC50 20 µg/mL), gossypetin-7-O-β-glucopyranoside (IC50 5.5 µg/mL), and hypolaetin-7-O-glucoside (IC50 5.7 µg/mL) in B. schreberi, and 5-[(8Z,11Z,14Z)-heptadeca-8,11,14-trienyl] resorcinol (IC50 5.3 µg/mL) not described to date in N. lotus. Five of these active constituents were detected in the traditional preparation. This work provides the first evidence for the ethnomedicinal use of these plants in the management of sleeping sickness in Angola.

3'-Demethoxy-6-O-Demethylisoguaiacin and Norisoguaiacin Nematocidal Lignans from Artemisia cina against Haemonchus contortus Infective Larvae

Artemisia cina is a plant used in traditional Chinese medicine as a remedy for parasitic diseases. This study describes the isolation and chemical characterization of anthelmintic compounds of A. cina against Haemonchus contortus infective larvae (L₃) through lethal testing. Previously, three extracts-n-hexane (HexAc), ethyl acetate (EtOAc) and methanol (MeOAc)-were evaluated at concentrations of 4 to 0.5 mg/mL, resulting in the HexAc extract with the greatest effect of 76.6% mortality of the larvae at 4 mg/mL. Then, this was chemically fractioned by polarity, obtaining seven fractions (C1F1-C1F7), and, when evaluated at concentrations from 2 to 0.25 mg/mL, the 2 mg/mL C1F5 fraction produced an effect against the nematode H. contortus of 100% mortality of the larvae. Thus, this fraction was fractionated again by column chromatography, obtaining twelve subfractions (C2F1-C2F12) which were evaluated from 1 to 0.125 mg/mL, with the C2F5 subfraction causing a nematicidal effect of 100% mortality. NMR analysis of one (¹H, ¹³C and DEPT) and two dimensions (COSY, HSQC and HMBC) and mass spectrometry of this fraction allowed us to identify the mixture of 3'-demethoxy-6-O-demethylisoguaiacin and norisoguaiacin. Therefore, it can be assumed that the mixture of these compounds is responsible for the anthelmintic effect. These results indicate that A. cina containing anthelmintic compounds and might be used as an antiparasitic drug against H. contortus.

Antitrypanosomal, Antitopoisomerase-I, and Cytotoxic Biological Evaluation of Some African Plants Belonging to Crassulaceae; Chemical Profiling of Extract Using UHPLC/QTOF-MS/MS

In our continuous study for some African plants as a source for antitrypanosomally and cytotoxic active drugs, nine different plants belonging to the Crassulaceae family have been selected for the present study. Sedum sieboldii leaves extract showed an antitrypanosomal activity against Trypanosoma brucei with an IC₅₀ value of 8.5 µg/mL. In addition, they have cytotoxic activities against (HCT-116), (HEPG-2) and (MCF-7), with IC₅₀ values of 28.18 ± 0.24, 22.05 ± 0.66, and 26.47 ± 0.85 µg/mL, respectively. Furthermore, the extract displayed inhibition against Topoisomerase-1 with an IC₅₀ value of 1.31 µg/mL. It showed the highest phenolics and flavonoids content among the other plants' extracts. In order to identify the secondary metabolites which may be responsible for such activities, profiling of the polar secondary metabolites of S. sieboldii extract via Ultra-Performance Liquid Chromatography coupled to High-Resolution QTOF-MS operated in negative and positive ionization modes, which revealed the presence of 46 metabolites, including flavonoids, phenolic acids, anthocyanidins, coumarin, and other metabolites.

Polyphenolic extracts from pomegranate and watermelon wastes as substrate to fabricate sustainable silver nanoparticles with larvicidal effect against Spodoptera littoralis

The agricultural wastes adversely affect the environment; however, they are rich in polyphenols; therefore, this study aimed to employ polyphenol-enriched waste extracts for silver nanoparticles synthesis, and study the larvicidal activity of silver nanoparticles fabricated by pomegranate and watermelon peels extracts (PPAgNPs and WPAgNPs) against all larval instars of Spodoptera littoralis. The polyphenol profile of pomegranate and watermelon peel extracts (PP and WP) and silver nanoparticles was detected by HPLC. The antioxidant activity was estimated by DPPH, and FARP assays and the antimicrobial activity was evaluated by disc assay. The Larvicidal activity of AgNPs against Egyptian leaf worm was performed by dipping technique. The obtained AgNPs were spherical with size ranged 15–85 nm and capped with proteins and polyphenols. The phenolic compounds in silver nanoparticles increased about extracts; therefore, they have the best performance in antioxidant/reducing activity, and inhibit the growth of tested bacteria and yeast. The PPAgNPs were the most effective against the first instar larvae instar (LC₅₀ = 68.32 µg/ml), followed by pomegranate extract with (LC₅₀ = 2852 µg/ml). The results indicated that obvious increase in polyphenols content in silver nanoparticles enhance their larvicidal effect and increasing mortality of 1^st larval of S. littoralis Egyptian leafworms causing additive effect and synergism. We recommend recycling phenolic enriched agricultural wastes in producing green silver nanoprticles to control cotton leafworm that causes economic loses to crops.

Polyhydroxybenzoic acid derivatives as potential new antimalarial agents

With more than 200 million cases and 400,000 related deaths, malaria remains one of the deadliest infectious diseases of 2021. Unfortunately, despite the availability of efficient treatments, we have observed an increase in people infected with malaria since 2015 (from 211 million in 2015 to 229 million in 2019). This trend could partially be due to the development of resistance to all the current drugs. Therefore, there is an urgent need for new alternatives. We have, thus, selected common natural scaffolds, polyhydroxybenzoic acids, and synthesized a library of derivatives to better understand the structure-activity relationships explaining their antiplasmodial effect. Only gallic acid derivatives showed a noticeable potential for further developments. Indeed, they showed a selective inhibitory effect on Plasmodium (IC₅₀ ~20 µM, SI > 5) often associated with interesting water solubility. Moreover, this has confirmed the critical importance of free phenolic functions (pyrogallol moiety) for the antimalarial effect. Methyl 4-benzoxy-3,5-dihydroxybenzoate (39) has, for the first time, been recognized as a potential lead for future research because of its marked inhibitory activity against Plasmodium falciparum and its significant hydrosolubility (3.72 mM).

In vitro anti-trypanosomal effects of selected phenolic acids on Trypanosoma brucei

African trypanosomiasis remains a lethal disease to both humans and livestock. The disease persists due to limited drug availability, toxicity and drug resistance, hence the need for a better understanding of the parasite’s biology and provision of alternative forms of therapy. In this study, the in vitro effects of phenolic acids were assessed for their trypanocidal activities against Trypanosoma brucei brucei. The effect of the phenolic acids on Trypanosoma brucei brucei was determined by the alamarBlue assay. The cell cycle effects were determined by flow cytometry and parasite morphological analysis was done by microscopy. Effect on cell proliferation was determined by growth kinetic analysis. Reverse Transcriptase quantitative Polymerase Chain Reaction was used to determine expression of iron dependent enzymes and iron distribution determined by atomic absorption spectroscopy. Gallic acid gave an IC₅₀ of 14.2±1.5 μM. Deferoxamine, gallic acid and diminazene aceturate showed a dose dependent effect on the cell viability and the mitochondrion membrane integrity. Gallic acid, deferoxamine and diminazene aceturate caused loss of kinetoplast in 22%, 26% and 82% of trypanosomes respectively and less than 10% increase in the number of trypanosomes in S phase was observed. Gallic acid caused a 0.6 fold decrease, 50 fold increase and 7 fold increase in the expression levels of the transferrin receptor, ribonucleotide reductase and cyclin 2 genes respectively while treatment with deferoxamine and diminazene aceturate also showed differential expressions of the transferrin receptor, ribonucleotide reductase and cyclin 2 genes.

The data suggests that gallic acid possibly exerts its effect on T. brucei via iron chelation leading to structural and morphological changes and arrest of the cell cycle. These together provide information on the cell biology of the parasite under iron starved conditions and provide leads into alternative therapeutic approaches in the treatment of African trypanosomiasis.

Antiparasitic activity in Asteraceae with special attention to ethnobotanical use by the tribes of Odisha, India

The purpose of this review is to survey the antiparasitic plants of the Asteraceae family and their applicability in the treatment of parasites. This review is divided into three major parts: (a) literature on traditional uses of Asteraceae plants for the treatment of parasites; (b) description of the major classes of chemical compounds from Asteraceae and their antiparasitic effects; and (c) antiparasitic activity with special reference to flavonoids and terpenoids. This review provides detailed information on the reported Asteraceae plant extracts found throughout the world and on isolated secondary metabolites that can inhibit protozoan parasites such as Plasmodium, Trypanosoma, Leishmania, and intestinal worms. Additionally, special attention is given to the Asteraceae plants of Odisha, used by the tribes of the area as antiparasitics. These plants are compared to the same plants used traditionally in other regions. Finally, we provide information on which plants identified in Odisha, India and related compounds show promise for the development of new drugs against parasitic diseases. For most of the plants discussed in this review, the active compounds still need to be isolated and tested further.

In vitro effects of Blepharocalyx salicifolius (H.B.K.) O. Berg on the viability of Echinococcus ortleppi protoscoleces

Scolicidal agents are important in the treatment of cystic echinococcosis. This study evaluated the scolicidal activity of the plant Blepharocalyx salicifolius (H.B.K.) Berg against Echinococcus ortleppi protoscoleces. The parasite species was identified by amplifying a fragment of the gene cytochrome c oxidase subunit 1 (COX 1). B. salicifolius crude extract at concentrations of 100, 200, 300 and 400 mg/mL was analyzed at different times (5, 10, 15, 30, 45 and 60 min). N-butanol and ethyl acetate fractions (100 and 200 mg/ mL) were also analyzed at 5, 10, 15 and 30 min. Both fractions showed 100% scolicidal activity at the concentration of 200 mg/mL at 5 min. Gallic acid, identified as the major compound of the ethyl acetate fraction- was responsible for the observed scolicidal activity. The results showed that crude extract and fractions of B. salicifolius have scolicidal effect against E. ortleppi protoscoleces.

Bumble bee parasite strains vary in resistance to phytochemicals

Nectar and pollen contain diverse phytochemicals that can reduce disease in pollinators. However, prior studies showed variable effects of nectar chemicals on infection, which could reflect variable phytochemical resistance among parasite strains. Inter-strain variation in resistance could influence evolutionary interactions between plants, pollinators, and pollinator disease, but testing direct effects of phytochemicals on parasites requires elimination of variation between bees. Using cell cultures of the bumble bee parasite Crithidia bombi, we determined (1) growth-inhibiting effects of nine floral phytochemicals and (2) variation in phytochemical resistance among four parasite strains. C. bombi growth was unaffected by naturally occurring concentrations of the known antitrypanosomal phenolics gallic acid, caffeic acid, and chlorogenic acid. However, C. bombi growth was inhibited by anabasine, eugenol, and thymol. Strains varied >3-fold in phytochemical resistance, suggesting that selection for phytochemical resistance could drive parasite evolution. Inhibitory concentrations of thymol (4.53–22.2 ppm) were similar to concentrations in Thymus vulgaris nectar (mean 5.2 ppm). Exposure of C. bombi to naturally occurring levels of phytochemicals—either within bees or during parasite transmission via flowers—could influence infection in nature. Flowers that produce antiparasitic phytochemicals, including thymol, could potentially reduce infection in Bombus populations, thereby counteracting a possible contributor to pollinator decline.

Achillea fragrantissima, rich in flavonoids and tannins, potentiates the activity of diminazine aceturate against Trypanosoma evansi in rats

OBJECTIVE

To evaluate activity of methanol extract of Achillea fragrantissima (meth) (A. fragrantissima) alone or in combination with diminazine aceturate (DA) against Trypanosoma evansi (T. evansi) in experimentally infected rats.

METHODS

Sixty adult male Wister albino rats were divided equally into 6 groups (A-F). Rats in groups A-E were experimentally infected with T. evansi and those in group F were uninfected. The groups were treated respectively as follows: group A-with 3.5 mg/kg DA; group B- with 1000 mg/kg meth A. fragrantissima; group C-3.5 mg/kg DA plus 500 mg/kg meth A. fragrantissima; group D-3.5 mg/kg DA plus 1000 mg/kg meth A. fragrantissima. Group E was left untreated. Parasitemia, survivability, packed cell volume, hemoglobin concentration, total leucocytes count, lymphocyte count, and serum malondialdehyde and reduced glutathione (GSH) levels were estimated. Phytochemical screening of meth A. fragrantissima was also performed.

RESULTS

The phytochemical analysis of the meth A. fragrantissima indicated a higher content from polyphenolic tannins and non tannins and flavonoids. The efficacy percentage against trypanosomiasis in groups A - E was respectively as follows 80, 40, 90, 100, 0. The administration of meth-A. fragrantissima (1000 mg/kg b.wt.) produced a moderate efficacy against trypanosomiasis. Untreated rats in group E died between 25 and 30 d post infection. The rats given DA and meth A. fragrantissima combinations (C and D) showed faster and higher recovery rates than the uninfected control and groups A and B. The initial reduction in packed cell volume, hemoglobin, total leucocytes count, increases in serum malondialdehyde and decreases in GSH levels were reversed by the treatments.

CONCLUSION

The administration of the methanol extracts of A. fragrantissima and DA combination therapy was more effective than each product alone in the treatment of rats infected with T. evansi and further studies are required to isolate more active ingredients.

Optimal Extraction of Gallic Acid fromSuaeda glaucaBge. Leaves and Enhanced Efficiency by Ionic Liquids

The ultrasound-assisted extraction (UAE) was initially applied to extract gallic acid fromSuaeda glaucaBge. using 70% ethanol as extraction solvent. Temperature, liquid-solid ratio, and extraction time were optimized by response surface methodology (RSM), obtaining maximum levels of gallic acid (6.30 mg·g−1) at 51°C, 19.52 mL·g−1, and 42.68 min, respectively. The obtained model was statistically significant (p<0.0001). The verification experiments at the optimum conditions yielded gallic acid for 6.21 mg·g−1. Subsequently, under optimal conditions, four ionic liquids were used to extract gallic acid fromSuaeda glaucaBge. The results indicated that the presence of 1-hexyl-3-methylimidazolium chloride allowed increasing the EE of gallic acid up to 8.90 mg·g−1. This might be interpreted in terms of the molecular interaction between ionic liquid and gallic acid. The use of ionic liquids involves a stronger gallic acid extraction capacity than conventional organic volatile solvents. A promising alternative process is proposed for the extraction of gallic acid ofSuaeda glaucaBge.

Novel Gallate Triphenylphosphonium Derivatives with Potent Antichagasic Activity

Chagas disease is one of the most neglected tropical diseases in the world, affecting nearly 15 million people, primarily in Latin America. Only two drugs are used for the treatment of this disease, nifurtimox and benznidazole. These drugs have limited efficacy and frequently induce adverse effects, limiting their usefulness. Consequently, new drugs must be found. In this study, we demonstrated the in vitro trypanocidal effects of a series of four gallic acid derivatives characterized by a gallate group linked to a triphenylphosphonium (TPP⁺) moiety (a delocalized cation) via a hydrocarbon chain of 8, 10, 11, or 12 atoms (TPP⁺-C₈, TPP⁺-C₁₀, TPP⁺-C₁₁, and TPP⁺-C₁₂, respectively). We analyzed parasite viability in isolated parasites (by MTT reduction and flow cytometry) and infected mammalian cells using T. cruzi Y strain trypomastigotes. Among the four derivatives, TPP⁺-C₁₀ and TPP⁺-C₁₂ were the most potent in both models, with EC₅₀ values (in isolated parasites) of 1.0 ± 0.6 and 1.0 ± 0.7 μM, respectively, and were significantly more potent than nifurtimox (EC₅₀ = 4.1 ± 0.6 μM). At 1 μM, TPP⁺-C₁₀ and TPP⁺-C₁₂ induced markers of cell death, such as phosphatidylserine exposure and propidium iodide permeabilization. In addition, at 1 μM, TPP⁺-C₁₀ and TPP⁺-C₁₂ significantly decreased the number of intracellular amastigotes (TPP⁺-C₁₀: 24.3%, TPP⁺-C₁₂: 19.0% of control measurements, as measured by DAPI staining) and the parasite’s DNA load (C₁₀: 10%, C₁₂: 13% of control measurements, as measured by qPCR). Based on the previous mode of action described for these compounds in cancer cells, we explored their mitochondrial effects in isolated trypomastigotes. TPP⁺-C₁₀ and TPP⁺-C₁₂ were the most potent compounds, significantly altering mitochondrial membrane potential at 1 μM (measured by JC-1 fluorescence) and inducing mitochondrial transition pore opening at 5 μM. Taken together, these results indicate that the TPP⁺-C₁₀ and TPP⁺-C₁₂ derivatives of gallic acid are promising trypanocidal agents with mitochondrial activity.

In vitro anti-Trichomonas vaginalis activity of Pistacia lentiscus mastic and Ocimum basilicum essential oil

Trichomonas vaginalis is a protozoan parasite that causes trichomoniasis; a cosmopolitan sexually transmitted disease. Metronidazole is the drug of choice for T. vaginalis infections. The increase in metronidazole resistant parasites and undesirable side effects of this drug makes the search for an alternative a priority for the management of trichomoniasis. Pistacia lentiscus mastic and Ocimum basilicum oil are known for their antibacterial, antifungal, antiviral and antiprotozoal effects. The present study was carried out to investigate the in vitro effects of P. lentiscus mastic and O. basilicum oil on T. vaginalis trophozoites. The effects of different concentrations of P. lentiscus mastic (15, 10 and 5 mg/ml) and different concentrations of O. basilicum oil (30, 20 and 10 μg/ml) on multiplication of trophozoites at different time points (after 24, 48, 72 and 96 h) were determined, also morphological changes were reported by transmission electron microscopy (TEM). The results showed that both plants caused an inhibition of growth of T. vaginalis trophozoites. The minimal lethal concentration of P. lentiscus mastic was 15 mg/ml after 24 h incubation, 10 mg/ml after 48 h and 5 mg/ml after 96 h. The minimal lethal concentration of O. basilicum oil was 30 μg/ml after 24 h incubation, 20 μg/ml after 48 h and 10 μg/ml after 96 h. TEM study of trophozoites treated by P. lentiscus mastic or by O. basilicum oil showed considerable damage of the membrane system of the trophozoites, and extensive vacuolization of the cytoplasm. These results highly suggest that P. lentiscus mastic and O. basilicum oil may be promising phytotherapeutic agents for trichomoniasis treatment.

Induction of morphological changes in Ustilago maydis cells by octyl gallate

The effects of octyl gallate on Ustilago maydis yeast cells were analysed in relation to its capacity to oxidize compounds (pro-oxidant actions). All phenolic compounds tested inhibited the alternative oxidase (AOX). However, only octyl gallate induced a morphological change in yeast cells and collapsed the mitochondrial membrane potential. In contrast to octyl gallate, propyl gallate and nordihydroguaiaretic acid caused only a negligible cell change and the membrane potential was not affected. Our findings show that structurally related phenolic compounds do not necessarily exert similar actions on target cells. Preincubation of U. maydis cells with trolox inhibited the change to pseudohyphal growth produced by octyl gallate. These results suggest that in addition to the inhibitory action of octyl gallate on the AOX, this compound induces a switch from yeast to a mycelium, probably through the formation of lipid peroxides.

Antitrypanosomal and antileishmanial activities of flavonoids and their analogues: in vitro, in vivo, structure-activity relationship, and quantitative structure-activity relationship studies

Trypanosomiasis and leishmaniasis are important parasitic diseases affecting millions of people in Africa, Asia, and South America. In a previous study, we identified several flavonoid glycosides as antiprotozoal principles from a Turkish plant. Here we surveyed a large set of flavonoid aglycones and glycosides, as well as a panel of other related compounds of phenolic and phenylpropanoid nature, for their in vitro activities against Trypanosoma brucei rhodesiense, Trypanosoma cruzi, and Leishmania donovani. The cytotoxicities of more than 100 compounds for mammalian L6 cells were also assessed and compared to their antiparasitic activities. Several compounds were investigated in vivo for their antileishmanial and antitrypanosomal efficacies in mouse models. Overall, the best in vitro trypanocidal activity for T. brucei rhodesiense was exerted by 7,8-dihydroxyflavone (50% inhibitory concentration [IC50], 68 ng/ml), followed by 3-hydroxyflavone, rhamnetin, and 7,8,3',4'-tetrahydroxyflavone (IC50s, 0.5 microg/ml) and catechol (IC50, 0.8 microg/ml). The activity against T. cruzi was moderate, and only chrysin dimethylether and 3-hydroxydaidzein had IC50s less than 5.0 microg/ml. The majority of the metabolites tested possessed remarkable leishmanicidal potential. Fisetin, 3-hydroxyflavone, luteolin, and quercetin were the most potent, giving IC50s of 0.6, 0.7, 0.8, and 1.0 microg/ml, respectively. 7,8-Dihydroxyflavone and quercetin appeared to ameliorate parasitic infections in mouse models. Generally, the test compounds lacked cytotoxicity in vitro and in vivo. By screening a large number of flavonoids and analogues, we were able to establish some general trends with respect to the structure-activity relationship, but it was not possible to draw clear and detailed quantitative structure-activity relationships for any of the bioactivities by two different approaches. However, our results can help in directing the rational design of 7,8-dihydroxyflavone and quercetin derivatives as potent and effective antiprotozoal agents.

Kola acuminata proanthocyanidins: a class of anti-trypanosomal compounds effective against Trypanosoma brucei

Human African trypanosomiasis is undergoing an alarming rate of recrudescence in many parts of sub-Saharan Africa. Yet, there is no successful chemotherapy for the disease due to a limited number of useful drugs, side effects and drawbacks of the existing medication, as well as the development of drug resistance by the parasite. Here we describe a new lead anti-trypanosomal compound isolated from Kola acuminata (Makasu). We purified a proanthocyanidin by chromatographic procedures and confirmed its homogeneity and structure by Nuclear Magnetic Resonance and Matrix-Assisted Laser Desorption Ionisation Time-of-Flight mass spectrometry, respectively. In vitro, this compound potently induced growth arrest and lysis of bloodstream form trypanosomes in a dose- and time-dependent manner. In a mouse model, it exhibited a trypanostatic effect that extended the life of infected, treated animals up to 8 days post-infection against the 4 days for infected, untreated animals. The proanthocyanidin showed a low cytotoxicity against mammalian cells, whereas treated-BF showed massive enlargement of their flagellar pocket and lysosome-like structures caused by an intense formation of multivesicular bodies and vesicles within these organelles. The observed ultrastructural alterations caused rupture of plasma membranes and the release of cell contents, indicative of a necrotic process rather than a programmed cell death. Interestingly, the proanthocyanidin acted against BF but not procyclic form trypanosomes. This new anti-trypanosomal compound should be further studied to determine its efficacy and suitability as an anti-trypanosomal drug and may be used as a tool to define novel specific drug targets in BF trypanosomes.

Potential therapeutic applications of some antinutritional plant secondary metabolites

Plant-based formulations have been used since ancient times as remedial measures against various human and animal ailments. Over the past 20 years interest in traditional medicines has increased considerably in many parts of the world. Whereas modifications in lifestyles, including diet, have had a profound effect on the increased risks of various diseases, there is considerable scientific evidence, both epidemiological and experimental, regarding vegetables and fruits as key features of diets associated with reduced risks of diseases such as cancers and infections. This has led to the use of a number of phytometabolites as anticarcinogenic and cardioprotective agents, promoting a dramatic increase in their consumption as dietary supplements. There are changing perceptions regarding the therapeutic potential of various plant secondary metabolites (PSMs), some of which have also been known to possess certain antinutritional qualities. The knowledge gained at the cellular and molecular levels, and biological activities of PSMs including tannin-polyphenols, saponins, mimosine, flavonoids, terpenoids, and phytates, would be useful in planning for future epidemiological studies and human cancer prevention trials, especially when a large pure dosage is not the option to deliver the active compounds to many tissues. It is well observed that alteration of cell cycle regulatory gene expression is frequently found in tumor tissues or cancer cell lines, and studies have suggested that the herbal-based or plant-originated cell cycle regulators might represent a new set of potential targets for anticancer drugs. The recent upsurge of interest in this area of research and advances made therein indicate that the impact of a number of diseases affecting humans and animals may be lessened, if not prevented, by simple dietary intake of PSMs with putative therapeutic properties.

Prooxidant action of gallic acid compounds: copper-dependent strand breaks and the formation of 8-hydroxy-2'-deoxyguanosine in DNA

Gallic acid and its alkylesters, polyphenolic compounds with antioxidative activity, acted as a prooxidant causing a copper-dependent DNA damage. Treatment of DNA from plasmid pBR322 and calf thymus with gallic acid plus copper ion caused strand scission and the formation of 8-hydroxy-2'-deoxyguanosine in DNA. Addition of catalase protected DNA from the gallic acid/copper-dependent strand breaks and the formation of 8-hydroxy-2'-deoxyguanosine, indicating that hydroxyl radical may participate in the DNA damage. Ethyl-, propyl- and butylgallates showed only a little DNA damage. Octyl- and laurylgallates caused negligible damage of DNA. DNA strand breaks and formation of 8-hydroxy-2'-deoxyguanosine were closely related to the reduction of copper by gallate compounds. These results imply that cuprous ion reduced by gallate derivatives may play a key role in the oxidative cleavage of DNA and the formation of base adduct. The cytotoxic effect of gallate compounds can be explained by their prooxidant action dependent on the reducing activity.

Leishmanicidal effect of curcumin in vitro

From a study to find anti-parasitic agents from natural resources, we found that curcumin showed the cytotoxicity against leishmania in vitro. The LD50 value of this activity was 37.6+/-3.5 microM.

In vitro antiprotozoal activity of extract and compounds from the stem bark of Combretum molle

The antiprotozoal activity of the Ethiopian medicinal plant Combretum molle (R. Br. ex G. Don.) Engl & Diels (Combretaceae) was evaluated by in vitro testing against Plasmodium falciparum, Trypanosoma brucei rhodesiense, Trypanosoma cruzi and Leishmania donovani. The acetone fraction of the stem bark of this plant prepared by soxhlet extraction was inactive against the intracellular amastigotes of L. donovani and T. cruzi in murine peritoneal macrophages but showed significant activity against extracellular T. b. rhodesiense blood stream form trypomastigotes and trophozoites of P. falciparum with IC(50) values of 2.19 and 8.17 microg/mL, respectively. Phytochemical examination of the bioactive fraction resulted in the isolation of two tannins and two oleanane-type pentacyclic triterpene glycosides. One of the tannins was identified as the ellagitannin, punicalagin, whilst the structure of the other (CM-A) has not yet been fully elucidated. The saponins that were characterized as arjunglucoside (also called 4-epi-sericoside) and sericoside displayed no activity against any of the four species of protozoa tested. On the other hand, punicalagin and CM-A had IC(50) values of 1.75 and 1.50 microM, respectively, against T. b. rhodesiense and were relatively less toxic to KB cells (cytotoxic/antiprotozoal ratios of 70 and 48, respectively). The tannins also showed intermediate activity against P. falciparum, although their selectivity against these parasites was less favourable than the above. It appears that our findings are the first report of hydrolysable tannins exhibiting antitrypanosomal and antiplasmodial activities.

New drugs for the treatment of human African trypanosomiasis: research and development

Chemotherapy of human African trypanosomiasis is problematic because of the high frequency of severe adverse events, the long duration and high cost of treatment, and an increasing number of treatment-refractory cases. New cost-efficient, easy-to-use drugs are urgently needed. Whereas basic research on potential drug targets is anchored in academia, the complex, highly regulated and very expensive process of preclinical and clinical drug development is almost exclusively in the hands of pharmaceutical companies. Jennifer Keiser, August Stich and Christian Burri here review, from the angle of industrial drug research and development, the past ten years of research activities at different stages of the development of trypanocidal drugs, and assess future prospects. The absence of compounds in clinical development Phases I-III indicates no new drugs will become available in the next few years.

EBV DNA polymerase inhibition of tannins from Eugenia uniflora

Nasopharyngeal carcinoma (NPC) is one of the high population malignant tumors among Chinese in southern China and southeast Asia. Epstein-Barr virus (EBV) is a human B lymphotropic herpes virus which is known to be closely associated with NPC. EBV DNA polymerase is a key enzyme during EBV replication and is measured by its radioactivity. The addition of phorbol 12-myristate 13-acetate to Raji cell cultures led to a large increase in EBV DNA polymerase, which was purified by sequential DEAE-cellulose, phosphocellulose and DNA-cellulose column chromatography. Four tannins were isolated from the active fractions of Eugenia uniflora L., which were tested for the inhibition of EBV DNA polymerase. The results showed the 50% inhibitory concentration (IC(50)) values of gallocatechin, oenothein B, eugeniflorins D(1) and D(2) were 26.5 62.3, 3.0 and 3.5 microM, respectively. Furthermore, when compared with the positive control (phosphonoacetic acid), an inhibitor of EBV replication, the IC(50) value was 16.4 microM. In view of the results, eugeniflorins D(1) and D(2) are the potency principles in the inhibition of EBV DNA polymerase from E. uniflora.