Antiprotozoal compounds from Asparagus africanus

Unusual Enzymatic C-C Bond Formation and Cleavage Reactions during Natural Product Biosynthesis

Natural products from plants and microorganisms provide a valuable reservoir of pharmaceutical compounds. C-C bond formation and cleavage are crucial events during natural product biosynthesis, playing pivotal roles in generating diverse and intricate chemical structures that are essential for biological functions. This review summarizes our recent findings regarding biosynthetic enzymes that catalyze unconventional C-C bond formation and cleavage reactions during natural product biosynthesis.

Structural and Mechanistic Insights into the C-C Bond-Forming Rearrangement Reaction Catalyzed by Heterodimeric Hinokiresinol Synthase

Hinokiresinol synthase (HRS) from Asparagus officinalis consists of two subunits, α and β, and catalyzes an unusual decarboxylative rearrangement reaction of 4-coumaryl 4-coumarate to generate (Z)-hinokiresinol with complete stereoselectivity. Herein, we describe the mechanism of rearrangement catalysis and the role played by the heterodimeric HRS, through structural and computational analyses. Our results suggest that the HRS reaction is unlikely to proceed via the previously hypothesized Claisen rearrangement mechanism. Instead, we propose that the 4-coumaryl 4-coumarate substrate is first cleaved into coumarate and an extended p-quinone methide, which then recombine to generate a new C-C bond. These processes are facilitated by proton transfers mediated by the basic residues (α-Lys164, α-Arg169, β-Lys168, and β-Arg173) in the cavity at the heterodimer interface. The active site residues, α-Asp165, β-Asp169, β-Trp17, β-Met136, and β-Ala171, play crucial roles in controlling the regioselectivity of the coupling between the fragmented intermediates as well as the stereoselectivity of the decarboxylation step, leading to the formation of the (Z)-hinokiresinol product.

Schweinfurthiamide, a new alkaloid isolated from the tuber roots of Asparagus flagellaris Baker (Liliaceae)

The phytochemical investigations of the tuber roots of Asparagus flagellaris led to the isolation of a new alkaloid, schweinfurthiamide (1) and eight known compounds. The structures of the isolated compounds were elucidated using spectroscopic techniques 1D and 2D NMR (1H, 13C, COSY, HMBC, HMQC, HSQC-TOCSY). The absolute configuration of 1 was unambiguously determined using DP4+ calculations. Compound 1 showed significant cytotoxicity against MCF-7 (breast cancer), NCI-H460 (lung cancer), and Hela (cervical cancer) cancer cell lines with IC50 values of 1.18 ± 0.02 µM, 2.25 ± 0.19 µM, and 4.23 ± 0.26 µM, respectively and no toxicity against normal human fibroblast (BJ).

Naturally occurring phenylethanoids and phenylpropanoids: antimalarial potential

Malaria as an infectious disease is one of the world's most dangerous parasitic diseases. There is an urgent need for the development of new antimalarial drugs. Natural products are a very rich source of new bioactive compounds. Our research aims to shed light on the recent studies which demonstrated the antimalarial potential of phenylpropanoids as a major natural-products class. This study involves an in silico analysis of naturally-occurring phenylpropanoids and phenylethanoids which showed 25 compounds with moderate to strong binding affinity to various amino acid residues lining the active site; P. falciparum kinase (PfPK5), P. falciparum cytochrome bc1 complex (cyt bc1), and P. falciparum lysyl-tRNA synthetase (PfKRS1); of Plasmodium falciparum parasite, a unicellular protozoan which causes the most severe and life-threatening malaria. Furthermore, the study was augmented by the assessment of antiplasmodial activity of glandularin, a naturally occurring dibenzylbutyrolactolic lignan, against chloroquine-sensitive 3D7 strain of P. falciparum using SYBR green I-based fluorescence assay, which showed high antimalarial activity with IC50 value of 11.2 μM after 24 hours of incubation. Our results highlight phenylpropanoids and glandularin in particular as a promising chemical lead for development of antimalarial drugs.

A review on new natural and synthetic anti-leishmanial chemotherapeutic agents and current perspective of treatment approaches

Leishmaniases are considered among the most neglected yet dangerous parasitic diseases worldwide. According to the recent WHO report (Weekly Epidemiological Record, Sep, 2021), 200 countries and territories reported leishmanises cases in 2020; of which 89 (45%) for CL, and 79 (40%) for VL were endemic. Indian subcontinent (India, Bangladesh and Nepal), one of the three eco-epidemiological hotspots of VL, currently reported 18% of the total cases of VL worldwide. Eastern Mediterranean region and the Region of the Americas together reported >90% of the new CL cases, of which >80% were from Afghanistan, Algeria, Brazil, Colombia, Iraq, Pakistan and the Syrian Arab Republic. While considering the current therapeutic options, conventional anti-leishmanial drugs have long been proved to be toxic and/or expensive and have resulted in extensive drug resistance in India. Recent searches for novel anti-leishmanial drugs have led to find out the prime cellular targets and metabolic pathways to bridge the gap between the known facts and unexplored data. Cutting edge knowledge based drug designing has simplified the search for novel molecules with leishmanicidal efficacy by identifying ligand-receptor interactions and has accelerated the cost effective primary discovery of molecules through computational validation against Leishmaniases. This review focuses on the limitations of conventional drugs, and discusses the chemotherapeutic potential of many novel natural and synthetic anti-leishmanial agents reported since the last decade. It is also interpreted that some of the reported molecules might be tested singly or as a part of combinatorial therapy on pre-clinical and clinical level.

Nephroprotective Effect of Asparagus africanus Lam. Root Extract against Gentamicin-Induced Nephrotoxicity in Swiss Albino Mice

The kidney is the organ most vulnerable to nephrotoxic drugs such as gentamicin. Nephrotoxicity is a rapid deterioration of kidney function due to various factors. Gentamicin causes nephrotoxicity, which was manifested by an increase in serum kidney biomarkers. Asparagus africanus is one of the ethnomedicinal plants used as traditional medicine for treating various ailments, including kidney disease in Ethiopian society. Thus, the aim of this study is to evaluate the nephroprotective effect of A. africanus root extract on gentamicin-induced nephrotoxicity. Using maceration techniques, 100 g of dried plant powder was extracted in 1 L of ethanol. The physicochemical screening of plant extracts revealed the presence of flavonoids, phenols, tannins, saponins, and steroids. The nephroprotective activity of A. africanus crude extract was evaluated on male Swiss albino mice. The crude ethanolic extract at 200 and 400 mg/kg doses showed strong nephroprotective effects by restoring biomarkers such as creatinine, uric acid, and blood urea nitrogen, which were damaged by gentamicin (p < 0.05) in a dose-dependent manner. The mice treated with higher doses (400 mg/kg) had a comparable nephroprotective effect compared to the positive control group (200 mg/kg silymarin; p > 0.05). The histopathology of the control group showed normal glomeruli, normal parenchyma, distal convoluted, and no tubular damage. The toxicant-induced group showed damage to glomeruli and inflammatory infiltration. Therefore, A. africanus root extract has a nephroprotective activity by retarding the gentamicin toxicity in male Swiss albino mice.

Medicinal Plants Used for Dermatological Disorders among the People of the Kingdom of Saudi Arabia: A Narrative Review

Historically, skin disorders have received less attention in health management than other life-threatening diseases that occur on a global scale. However, numerous skin problems are reported to primary health care systems worldwide, particularly in tropical locations. While modern physicians often address most skin conditions, it is estimated that over 70% of individuals with skin illnesses do not seek treatment. Traditional medicine dates all the way back to human civilization's inception. Numerous materials are utilized in traditional medicinal remedies, but the use of plants is particularly critical. Saudi Arabia is one of the world's most botanically varied countries, having an extensive folk medicine heritage. While several reviews on the use of plants to cure skin disorders has been published worldwide, very few have been undertaken in Saudi Arabia, much alone a comprehensive one. Thus, the present review identified the most significant and medicinally relevant herbs used in the treatment of various dermatological conditions in Saudi Arabia. A total of 43 plants were identified and described in this study. This investigation omitted publications that lacked detailed data and had only fragmented information regarding the herb's traditional use in topical applications.

Neuro-nutraceutical potential of Asparagus racemosus: A review

Debilitating neuropsychiatric and neurodegenerative conditions are associated with complex multifactorial pathophysiology. Their treatment strategies often only provide symptomatic relief, delaying disease progression without giving a complete cure. Potent and safer treatment alternatives beyond symptomatic relief are sought. Herbal supplements have surely been explored due to their multiple component nature to enhance the effect of western medications. One such well-documented nutraceutical in the ancient Greek, Chinese, and Ayurvedic medicine system known for its various medicinal benefits is Asparagus racemosus. Widely used for its lactogenic properties, A. racemosus is also cited in Ayurveda as a nervine tonic. A. racemosus based nutraceuticals have shown to possess adaptogenic, neuroprotective, antioxidant, anti-inflammatory, and nootropic activity under preclinical and clinical settings without posing significant adverse effects. A. racemosus extracts restore the perturbed neurotransmitters and prevent oxidative neuronal damage. From the available neuropharmacological researches, the physiological actions of A. racemosus can ultimately be directed for either augmentation of cognitive ability or in the management of neurological conditions such as stress, anxiety, depression, epilepsy, Parkinson's, and Alzheimer's disease. The studies focus on the multi-component extract, and the lack of standardization has been a major hurdle in preventing the allotment of reported neuropharmacological activity to one of the phytoconstituent. Herbal standardization of the plant extract based on a specific biomarker can help elucidate the intricate biomolecular pathway and neurocircuitries being involved. This, followed by rigorous standardized clinical trials, fixing dosages, and determining contraindications would facilitate the translation of A. racemosus to a FDA-approved neuromedicine for neurological disorders.

Antileishmanial Activity of Lignans, Neolignans, and Other Plant Phenols

Secondary metabolites (SM) from organisms have served medicinal chemists over the past two centuries as an almost inexhaustible pool of new drugs, drug-like skeletons, and chemical probes that have been used in the "hunt" for new biologically active molecules with a "beneficial effect on human mind and body." Several secondary metabolites, or their derivatives, have been found to be the answer in the quest to search for new approaches to treat or even eradicate many types of diseases that oppress humanity. A special place among SM is occupied by lignans and neolignans. These phenolic compounds are generated biosynthetically via radical coupling of two phenylpropanoid monomers, and are known for their multitarget activity and low toxicity. The disadvantage of the relatively low specificity of phenylpropanoid-based SM turns into an advantage when structural modifications of these skeletons are made. Indeed, phenylpropanoid-based SM previously have proven to offer great potential as a starting point in drug development. Compounds such as Warfarin^® (a coumarin-based anticoagulant) as well as etoposide and teniposide (podophyllotoxin-based anticancer drugs) are just a few examples. At the beginning of the third decade of the twenty-first century, the call for the treatment of more than a dozen rare or previously "neglected" diseases remains for various reasons unanswered. Leishmaniasis, a neglected disease that desperately needs new ways of treatment, is just one of these. This disease is caused by more than 20 leishmanial parasites that are pathogenic to humans and are spread by as many as 800 sandfly species across subtropical areas of the world. With continuing climate changes, the presence of Leishmania parasites and therefore leishmaniasis, the disease caused by these parasites, is spreading from previous locations to new areas. Thus, leishmaniasis is affecting each year a larger proportion of the world's population. The choice of appropriate leishmaniasis treatment depends on the severity of the disease and its form of manifestation. The success of current drug therapy is often limited, due in most cases to requiring long hospitalization periods (weeks to months) and the toxicity (side effects) of administered drugs, in addition to the increasing resistance of the parasites to treatment. It is thus important to develop new drugs and treatments that are less toxic, can overcome drug resistance, and require shorter periods of treatment. These aspects are especially important for the populations of developing countries. It was reported that several phenylpropanoid-based secondary metabolites manifest interesting antileishmanial activities and are used by various indigenous people to treat leishmaniasis. In this chapter, the authors shed some light on the various biological activities of phenylpropanoid natural products, with the main focus being on their possible applications in the context of antileishmanial treatment.

An investigation of the antileishmanial properties of semi-synthetic saponins

Leishmaniasis is a neglected tropical disease caused by insect-vector borne protozoan parasites of the, Leishmania species. Whilst infection threatens and affects millions of the global poor, vaccines are absent and drug therapy limited. Extensive efforts have recently been made to discover new leads from small molecule synthetic compound libraries held by industry; however, the number of new chemical entities identified and entering development as anti-leishmanials has been very low. This has led to increased interest in the possibility of discovering naturally derived compounds with potent antileishmanial activity which may be developed towards clinical applications. Plant-derived triterpenoid and steroidal saponins have long been considered as anti-microbials and here we describe an investigation of a library of 137 natural (9) and semi-synthetic saponins (128) for activity against Leishmania mexicana, a causative agent of cutaneous leishmaniasis. The triterpenoid sapogenin, hederagenin, readily obtained in large quantities from Hedera helix (common ivy), was converted into a range of 128 derivatives. These semi-synthetic compounds, as well as saponins isolated from ivy, were examined with a phenotypic screening approach to identify potent and selective anti-leishmanial hits. This led to the identification of 12 compounds, including the natural saponin gypsogenin, demonstrating high potency (ED50 < 10.5 μM) against axenic L. mexicana amastigotes, the mammalian pathogenic form. One of these, hederagenin disuccinate, was sufficiently non-toxic to the macrophage host cell to facilitate further analyses, selectivity index (SI) > 10. Whilst this was not active in an infected cell model, the anti-leishmanial properties of hederagenin-derivatives have been demonstrated, and the possibility of improving the selectivity of natural hederagenin through chemical modification has been established.

Nor-Lignans: Occurrence in Plants and Biological Activities-A Review

In this review article, the occurrence of nor-lignans and their biological activities are explored and described. Nor-lignans have proven to be present in several different families also belonging to chemosystematically distant orders as well as to have many different beneficial pharmacological activities. This review article represents the first one on this argument and is thought to give a first overview on these compounds with the hope that their study may continue and increase, after this.

Treatment of malaria and related symptoms using traditional herbal medicine in Ethiopia

ETHNOPHARMACOLOGICAL RELEVANCE

Medicinal plants have always been an integral part of different cultures in Ethiopia in the treatment of different illnesses including malaria and related symptoms. However, due to lack of proper documentation, urbanization, drought, acculturation and deforestation, there is an increased risk of losing this traditional knowledge. Hence, the use of the indigenous knowledge should be well documented and validated for potential future use.

AIM OF THE STUDY

To gather and document information on medicinal plants which are used in the traditional treatment of malaria and related symptoms in Ethiopia.

MATERIALS AND METHODS

First, an ethnomedicinal survey of plants was conducted in 17 districts of Jimma zone, the Oromia national regional state of Ethiopia. Jimma zone is malarious and rich in natural flora. A total of 115 traditional healers were interviewed using a semi-structured questionnaire containing personal data of the respondents, and information on medicinal plants used to treat malaria and related symptoms. In addition, a literature search using Medline/PubMed, Google Scholar, ScienceDirect and HINARI was conducted on the indigenous use, in-vitro/in-vivo anti-malarial activity reports, and the chemical characterization of medicinal plants of Ethiopia used against malaria.

RESULTS

From ethnomedicinal survey, a total of 28 species of plants used in the traditional treatment of malaria and related symptoms in Jimma Zone were collected, identified and documented. In addition, the literature search revealed that 124 medicinal plant species were reported to be traditionally used in the treatment of malaria in Ethiopia. From both ethnomedicinal survey and the literature search, Asteraceae and Fabaceae were the most represented families and Allium sativum L., Carica papaya L., Vernonia amygdalina Del., Lepidium sativum L. and Croton macrostachyus Del. were the most frequently reported plant species for their anti-malarial use. The dominant plant parts used in the preparation of remedies were leaves. About 54% of the medicinal plants documented in the survey have been reported as an anti-malarial plant in the literature search. Furthermore, the in-vitro and in-vivo anti-plasmodial activity reports of extracts from some of plant species were found to support the traditional claim of the documented plants. Moreover, literatures indicate that several secondary metabolites isolated from certain plant species that are traditionally used for the treatment of malaria and related symptoms in Ethiopia demonstrate strong anti-plasmodial activity.

CONCLUSIONS

The result of the current study showed that traditional knowledge is still playing an important role in the management of malaria and related symptoms in Ethiopia. Allium sativum L., Carica papaya L., Vernonia amygdalina Del., and Lepidium sativum L. are the most commonly reported species as anti-malarial plants and the traditional claim of some species was supported by known anti-plasmodial activity and bioactivity reports. The finding of this study is important in the rational prioritization of plant species which are potentially used for investigating new compounds, which could be efficacious for malaria treatment.

Bioactive Neolignans and Other Compounds from Magnolia grandiflora L.: Isolation and Antiplasmodial Activity

Bioassay-guided fractionation of a methanol extract of Magnolia grandiflora against Plasmodium falciparum yielded two new (1 and 2) and six known (3 - 8) bioactive compounds. The structures of the new compounds were assigned by mass spectrometric and 1D- and 2D-NMR data. Known compounds were identified by comparison of ¹ H-NMR and MS data with literature data. The two known neolignans 3 and 4 showed moderate antiplasmodial activity with the IC₅₀ values of 2.8 ± 0.1 and 3.4 ± 0.1 μm, respectively. Weak antiplasmodial activity was recorded for compounds 1, 2, 5, 6, 7, and 8, with the IC₅₀ values of 38 ± 2, 23 ± 2, 16.5 ± 0.2, 86 ± 1, 44 ± 4, and 114 ± 9 μm, respectively.

Systematic review on traditional medicinal plants used for the treatment of malaria in Ethiopia: trends and perspectives

Background

Ethiopia is endowed with abundant medicinal plant resources and traditional medicinal practices. However, available research evidence on indigenous anti-malarial plants is highly fragmented in the country. The present systematic review attempted to explore, synthesize and compile ethno-medicinal research evidence on anti-malarial medicinal plants in Ethiopia.

Methods

A systematic web search analysis and review was conducted on research literature pertaining to medicinal plants used for traditional malaria treatment in Ethiopia. Data were collected from a total of 82 Ethiopian studies meeting specific inclusion criteria including published research articles and unpublished thesis reports. SPSS Version 16 was used to summarize relevant ethno-botanical/medicinal information using descriptive statistics, frequency, percentage, tables, and bar graphs.

Results

A total of 200 different plant species (from 71 families) used for traditional malaria treatment were identified in different parts of Ethiopia. Distribution and usage pattern of anti-malarial plants showed substantial variability across different geographic settings. A higher diversity of anti-malarial plants was reported from western and southwestern parts of the country. Analysis of ethno-medicinal recipes indicated that mainly fresh leaves were used for preparation of remedies. Decoction, concoction and eating/chewing were found to be the most frequently employed herbal remedy preparation methods. Notably, anti-malarial herbal remedies were administered by oral route. Information on potential side effects of anti-malarial herbal preparations was patchy. However, some anti-malarial plants were reported to have potentially serious side effects using different local antidotes and some specific contra-indications.

Conclusion

The study highlighted a rich diversity of indigenous anti-malarial medicinal plants with equally divergent herbal remedy preparation and use pattern in Ethiopia. Baseline information gaps were observed in key geographic settings. Likewise, herbal remedy toxicity risks and countermeasures generally entailed more exhaustive investigation. Experimental research and advanced chemical analysis are also required to validate the therapeutic potential of anti-malarial compounds from promising plant species.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-017-1953-2) contains supplementary material, which is available to authorized users.

Landolphia owariensis leaf extracts reduce parasitemia in Plasmodium berghei-infected mice

Context Landolphia owariensis P. Beauv. (Apocyanaceae) leaf is used in southeast Nigeria to treat malaria. Objective This study evaluated the antiplasmodial activity of L. owariensis leaf extract and fractions, also the phytoconstituents were standardized and analyzed. Methods The effects of daily, oral administrations of 200, 400 and 800 mg/kg of L. owariensis leaf extract (LOE), its hexane (LOHF), ethyl acetate (LOEF) and methanol (LOMF) fractions on early, established and residual infections in Plasmodium berghei-infected albino mice were evaluated in vivo. The extract and fractions were subjected to phytochemical analysis and HPLC fingerprinting, and the acute toxicity of LOE was evaluated. Results The extract and fractions elicited 29-86, 18-95 and 75-96% significant (p < 0.001) suppression of parasitemia in early, established and residual infections, respectively. The ED50 values for suppressive activity of LOE, LOHF, LOEF and LOMF were 266.56, 514.93, 392.95 and 165.70 mg/kg, respectively. The post-day 30-survival index was 16.7-50, 16.7, 16.7-66.7 and 50-83.3% for LOE, LOHF, LOEF, and LOMF, respectively. Extract-treated mice significantly (p < 0.001) gained weight and had reduced mortality compared with negative control (untreated) mice. An oral LD50 value  >5000 mg/kg in mice was established for LOE. The LOMF showed the greatest antiplasmodial activity in all the models, suggesting that the antimalarial activity of the plant may be attributed to alkaloids, flavonoids, saponins and tannins present in the fraction. Conclusion Results demonstrate the antiplasmodial activity of L. owariensis leaf, and provide a pharmacological rationale for its ethnomedicinal use as an antimalarial agent.

Syntheses and Anti-inflammatory Activity of Natural 1,3-Diarylpropenes

First syntheses of five natural 1,3-diarylpropenes (cinnamylphenols) 2-4, 7, and 8 along with synthesis of two other natural 1,3-diarylpropenes 1 and 5 and E-isomer of mucronulastyrene (6) were achieved by Friedel-Crafts alkylation as a key step. Subsequently, their anti-inflammatory effects were also investigated in lipopolysaccharide (LPS)-induced RAW264.7 macrophages. The compounds exhibited significant inhibition of inflammatory mediated nitric oxide (NO) production with no cytotoxicity except compound 8 (dalberatin B) at 10 µM concentration and IC50 values were found in the range from 4.05 to 16.76 µM.

Analysis of cultivable microbiota and diet intake pattern of the long-lived naked mole-rat

BACKGROUND

A variety of microbial communities exist throughout the human and animal body. Genetics, environmental factors and long-term dietary habit contribute to shaping the composition of the gut microbiota. For this reason the study of the gut microbiota of a mammal exhibiting an extraordinary life span is of great importance. The naked mole-rat (Heterocephalus glaber) is a eusocial mammal known for its longevity and cancer resistance.

METHODS

Here we analyzed its gut microbiota by cultivating the bacteria under aerobic and anaerobic conditions and identifying their species by mass spectrometry.

RESULTS

Altogether, 29 species of microbes were identified, predominantly belonging to Firmicutes, and Bacteroidetes. The most frequent species were Bacillus megaterium (45.2 %), followed by Bacteroides thetaiotaomicron (19.4 %), Bacteroides ovatus, Staphylococcus sciuri and Paenibacillus spp., each with a frequency of 16.1 %.

CONCLUSION

Overall, the gut of the naked mole-rat is colonized by diverse, but low numbers of cultivable microbes compared with humans and mice. The primary food plants of the rodents are rich in polyphenols and related compounds, possessing anti-microbial, anti-inflammatory, anti-oxidative as well as anti-cancer activity which may contribute to their exceptionally healthy life.

Toxicological study of the butanol fractionated root extract of Asparagus africanus Lam., on some blood parameter and histopathology of liver and kidney in mice

BACKGROUND

The butanol fractionated root extract of Asparagus africanus Lam., a traditional herb widely used to treat various ailments were analyzed for the presence of potential toxicity after single (acute) and repeated (subchronic) dose oral administration in adult swiss albino mice using gavages.

METHODS

For the acute study, butanol fractionated extract of the plant was administered in single doses of 1000, 3000 and 5000 mg/kg body weight. In the sub-chronic dose study, the extract was administered at doses of 300 and 600 mg/kg body weight/day for 42 days. Selected hematological and biochemical parameters of the blood followed by histopathological analysis were investigated after 42 days of daily administrations. The results were expressed as M ± SE, and differences at P < 0.05 was considered significant. One way analysis of variance (ANOVA) and least significant difference tests were employed to check the significant differences between the various parameters of the experimental groups.

RESULTS

In the acute study, the extract did not caused dose-dependent general behavioral adverse effects, body weight change and mortality. The single dose toxicity studies therefore showed that the butanol fraction of the extract has high safety profile when given orally. After 42 days of daily dosing, in the sub-chronic study, no clinically significant changes were observed for hematological and biochemical parameters. Except an occasional small number of focal mononuclear lymphocytic cells infiltrations around the central and portal triad of the liver of a few mice, the histopathological parameters do not show significant change.

CONCLUSION

It is concluded that, the butanol fractionated extract from A. africanus at the given dose does not show significant toxicity. The presence of focal inflammation on the liver of a few mice may be associated to the presence of flavonoid glycoside in the butanol fractionated extract.

Ethnobotanical survey of traditionally used medicinal plants for infections of skin, gastrointestinal tract, urinary tract and the oral cavity in Borabu sub-county, Nyamira county, Kenya

ETHNOPHARMACOLOGICAL RELEVANCE

Different communities throughout the world have specialized and profound knowledge on the use medicinal plants for various diseases. However, the detailed information on the respective use may extinct in near future as this knowledge is passed only orally among generations in most of the communities.

AIM OF THE STUDY

The present survey aimed to document the use of medicinal plants by traditional healers from the Kisii community, Borabu sub-county in Nyamira county, Kenya, to treat infections of the urinary tract, oral cavity, gastrointestinal system and the skin and to evaluate the social context in which the healers work and practice.

MATERIALS AND METHODS

Validated questionnaires were applied to 50 traditional healers in the study region, followed by interviews and structured conversations. Information on the relevant traditionally used medicinal plants and their use were documented, including sampling and identification of voucher specimens.

RESULTS

The ethnopharmacological survey revealed 25 medicinal plant species belonging to 19 families. It got evident that most of these species will be extinct in the near future unless appropriate measures are taken, as it turned out difficult to collect some of the wild growing species. Elaeodendron buchananii Loes, Erlangea marginata S. Moore, Acacia gerrardii Benth., Balanites orbicularis Sprague, Solanum renschii Vatke and Orthosiphon hildebrandtii Vatke have not been described before for its medicinal use. Among the 25 species collected from the various regions of Borabu sub-county Urtica dioica L. was the only medicinal plant that was collected from all regions. In contrast Erythrina abyssinica and Rhus natalensis were found in only two regions of the study area.

CONCLUSION

The traditional medicinal use of the reported plants for infections should be documented and a great need of awareness from scientists and local government for improved preservation or field cultivation of some species is obvious.

In vivo Antimalarial Activities of Russelia Equisetiformis in Plasmodium Berghei Infected Mice

The rising problem of resistance to most commonly used antimalarials remains a major challenge in the control of malaria suggesting the need for new antimalarial agents. This work explores the antiplasmodial potential of ethanol extract of Russelia equisetiformis in chloroquine Plasmodium berghei infected mice. Swiss albino mice were intraperitoneally infected with chloroquine-resistant P. berghei (ANKA). Experimental mice were treated for four days consecutively with graded doses of plant extracts and standard antimalarial drugs (artesunate and chloroquine) at a dose of 10 mg/kg body weight used as control. The extract showed a dose-dependent activity in the chemosuppression of P. berghei parasites by 31.6, 44.7, 48.4 and 86.5% at doses of 100, 200, 400 and 800 mg/kg, while chloroquine (10 mg/kg) and artesunate produced 59.4 and 68.4%, respectively. The extract showed a significant decrease in parasitaemia (P<0.05). The level of parasitemia and decrease in weight in all the treated groups was significantly lower (P<0.05) compared with the infected but untreated mice. The plant extract was devoid of toxicity at the highest dose tested (5000 mg/kg). The study concluded that the ethanol extract of R. equisetiformis possesses antimalarial effect, which supports the folk medicine claim of its use in the treatment of malaria.

The potential of anti-malarial compounds derived from African medicinal plants, part II: a pharmacological evaluation of non-alkaloids and non-terpenoids

Malaria is currently a public health concern in many countries in the world due to various factors which are not yet under check. Drug discovery projects targeting malaria often resort to natural sources in the search for lead compounds. A survey of the literature has led to a summary of the major findings regarding plant-derived compounds from African flora, which have shown anti-malarial/antiplasmodial activities, tested by in vitro and in vivo assays. Considerations have been given to compounds with activities ranging from "very active" to "weakly active", leading to >500 chemical structures, mainly alkaloids, terpenoids, flavonoids, coumarins, phenolics, polyacetylenes, xanthones, quinones, steroids and lignans. However, only the compounds that showed anti-malarial activity, from "very active" to "moderately active", are discussed in this review.

Antiplasmodial potential of selected medicinal plants from eastern Ghats of South India

Malaria caused by the protozoan parasite Plasmodium falciparum, is a major health problem of the developing world. In the present study medicinal plants from Eastern Ghats of South India have been extracted with ethyl acetate and assayed for growth inhibition of asexual erythrocytic stages of chloroquine (CQ)-sensitive (3D7) and (CQ)-resistant (INDO) strains of P. falciparum in culture using the fluorescence-based SYBR Green I assay. Studied extracts showed a spectrum of antiplasmodial activities ranging from (a) very good (IC(50)<10-10 μg/mL: Cyperus rotundus and Zingiber officinale); (b) good (IC(50), >10-15 μg/mL: Ficus religiosa and Murraya koenigii); (c) moderate (IC(50)>15-25 μg/mL: Ficus benghalensis); (d) poor activity (IC(50)>25-60 μg/mL) and (e) inactive (IC(50)>60 μg/mL). Resistance indices ranging from 0.78 to 1.28 suggest that some of these extracts had equal promise against the CQ resistant INDO strain of P. falciparum. Cytotoxicity assessment of the extracts against HeLa cell line using MTT assay revealed that the selectivity indices in the range of 3-15 suggesting a good margin of safety.

In vitro antimicrobial activity of extracts from plants used traditionally in South Africa to treat tuberculosis and related symptoms

Respiratory ailments are major human killers, especially in developing countries. Tuberculosis (TB) is an infectious disease causing a threat to human healthcare. Many South African plants are used in the traditional treatment of TB and related symptoms, but there has not been a sufficient focus on evaluating their antimicrobial properties. The aim of this study was to evaluate the antimicrobial properties of plants used traditionally to treat TB and related symptoms against microorganisms (Klebsiella pneumoniae, Staphylococcus aureus, and Mycobacterium aurum A+) associated with respiratory infections using the microdilution assay. Ten plants were selected based on a survey of available literature of medicinal plants used in South Africa for the treatment of TB and related symptoms. The petroleum ether, dichloromethane, 80% ethanol, and water extracts of the selected plants were evaluated for antibacterial activity. Out of 68 extracts tested from different parts of the 10 plant species, 17 showed good antimicrobial activities against at least one or more of the microbial strains tested, with minimum inhibitory concentration ranging from 0.195 to 12.5 mg/mL. The good antimicrobial properties of Abrus precatorius, Terminalia phanerophlebia, Indigofera arrecta, and Pentanisia prunelloides authenticate their traditional use in the treatment of respiratory diseases. Thus, further pharmacological and phytochemical analysis is required.

Chemical constituents of Asparagus

Asparagus species (family Liliaceae) are medicinal plants of temperate Himalayas. They possess a variety of biological properties, such as being antioxidants, immunostimulants, anti-inflammatory, antihepatotoxic, antibacterial, antioxytocic, and reproductive agents. The article briefly reviews the isolated chemical constituents and the biological activities of the plant species. The structural formula of isolated compounds and their distribution in the species studied are also given.

Malaria in the Renaissance: remedies from European herbals from the 16th and 17th century

BACKGROUND

From antiquity up into the 20th century tertian and quartan malaria which are caused by the parasites Plasmodium vivax and Plasmodium malariae were widespread in Central Europe. Hundreds of different remedies against malaria can be found in herbals from the Renaissance.

AIM OF THE STUDY

To document and discuss from a modern pharmacological viewpoint the old remedies described in eight 16th and 17th century herbals written in German.

MATERIALS AND METHODS

Eight of the most important herbals of the 16th and 17th century including Bock (1577), Fuchs (1543), Matthiolus (1590), Lonicerus (1560), Brunfels (1532), Zwinger (1696), and Tabernaemontanus (1591 and 1678) were searched for terms related to malaria, and documented plants and recipes described for its treatment. Additionally the overlapping of these remedies with those in De Materia Medica by the Greek physician Dioscorides was studied.

RESULTS

Three hundred and fourteen taxa were identified in the herbals for this indication. Recent pharmacological data was found for just 5% of them. The influence of De Materia Medica was shown to be negligible with only 3.5% of the remedies in common.

CONCLUSIONS

European Renaissance herbals may be a valuable source of information for the selection of plants for focussed antiplasmodial screening programmes, but have received only little scientific attention. Antimalarial remedies from these herbals must be viewed as independent sources of knowledge separate from Dioscorides' De Materia Medica.

Analgesic and anti-inflammatory activities of Asparagus africanus root extract

The methanolic extract of the roots of Asparagus africanus Lam (Liliaceae) which contains mainly saponins and carbohydrate showed significant analgesic and anti-inflammatory activities (P<0.05) in the tail-flick/hot-plate test and egg albumen-induced rat paw oedema tests that were comparable to the test drugs (morphine 20 mg/kg and indomethacin 50 mg/kg respectively). These results indicate that the extract possesses analgesic and anti-inflammatory properties.

Racemoside A, an anti-leishmanial, water-soluble, natural steroidal saponin, induces programmed cell death in Leishmania donovani

Leishmaniasis remains a major health problem of the tropical and subtropical world. The visceral form causes the most fatalities if left untreated. Dramatic increases in the rates of infection and drug resistance and the non-availability of safe vaccines have highlighted the need for identification of novel and inexpensive anti-leishmanial agents. This study reports that racemoside A, a water-soluble steroidal saponin purified from the fruits of Asparagus racemosus, is a potent anti-leishmanial molecule effective against antimonial-sensitive (strain AG83) and -unresponsive (strain GE1F8R) Leishmania donovani promastigotes, with IC(50) values of 1.15 and 1.31 microg ml(-1), respectively. Incubation of promastigotes with racemoside A caused morphological alterations including cell shrinkage, an aflagellated ovoid shape and chromatin condensation. This compound exerts its leishmanicidal effect through the induction of programmed cell death mediated by the loss of plasma membrane integrity as detected by binding of annexin V and propidium iodide, loss of mitochondrial membrane potential culminating in cell-cycle arrest at the sub-G(0)/G(1) phase, and DNA nicking shown by deoxynucleotidyltransferase-mediated dUTP end labelling (TUNEL). Racemoside A also showed significant activity against intracellular amastigotes of AG83 and GE1F8R at a 7-8-fold lower dose, with IC(50) values of 0.17 and 0.16 microg ml(-1), respectively, and was non-toxic to murine peritoneal macrophages up to a concentration of 10 microg ml(-1). Hence, racemoside A is a potent anti-leishmanial agent that merits further pharmacological investigation.

Steroidal saponins from Asparagus acutifolius

Six new steroidal saponins (1-6) were isolated from the roots of A. acutifolius L., together with a known spirostanol glycoside (7). Their structures were elucidated mainly by extensive spectroscopic analysis (1D and 2D NMR, FABMS and HRESIMS). Compounds 4-7 demonstrated antifungal activity against the human pathogenic yeasts C. albicans, C. glabrata and C. tropicalis with MICs values between 12.5 and 100 microg/ml.

Spirostanol Saponins from Asparagus sprengeri and Their Molluscicidal Activity

Two new spirostane saponins namely (25 R)-6α-[(β-D-glucopyranosyl)oxy]-5α-spirostan-3β-yl β-D-galactopyranoside (1) and (25 R)-6α-[(β-D-glucopyranosyl)oxy]-27-hydroxy-5α-spirostan-3β-yl β-D-glucopyranoside (2), together with three known metabolites (25 S)-5β-spirostan-3-β-yl O-β-D-glucopyranosyl-(1→2)-β-D-glucopyranoside (3), (25 R)-5α-spirostan-3-β-yl O-β-D-galactopyranosyl-(1→2)- O-β-D-glucopyranosyl-(1→4)-β-D-galactopyranoside (4) and (25 R)-5α-spirostan-3-β-yl O-β-D-glucopyranosyl-(1→3)- O-[β-D-xylopyranosyl-(1→2)]- O-β-D-glucopyranosyl-(1→4)-β-D-glactopyranoside (5) were identified from the leaves of Asparagus sprengeri Regel (Asparagaceae). Determination of the structures was based on chemical and spectroscopic data (HRESI-MS/MSn, 1H, DEPT 13C NMR, 1H-1H COSY, HSQC and HMBC). The dry powder, the 1-butanol extract of the leaves, and the isolated compounds (3–5) exhibited molluscicidal properties against Biomphalaria alexandrina snails (the intermediate host of Schistosoma mansoni) [LC90 = 150, 40, 7, 10 and 13 ppm, respectively], while compounds 1 and 2 were molluscicidally inactive.

Anti-leishmanial Activity of Justicidone and its Synthetic Precursors

Justicidone, a C-5, C-8 dioxo-lignan of the arylnaphthalene type isolated from Justicia hyssopifolia, and its synthetic precursors were tested for the activity against Leishmania braziliensis and Leishmania amazonensis promastigotes in vitro. Justicidone showed activity against L. braziliensis with an IC50 of 181.90 μM, while, the diasteromeric mixture of one of its synthetic precursors exhibited activity against both parasite strains with an IC50 of 99.27 μM (L. braziliensis) and 181.75 μM (L. amazonensis). This activity has not previously been reported for dibenzylbutyrolactones and dioxo-lignans.

A review of natural products with antileishmanial activity

Infections caused by protozoa of the genus Leishmania are a major worldwide health problem, with high endemicity in developing countries. The incidence of the disease has increased since the emergence of AIDS. In the absence of a vaccine, there is an urgent need for effective drugs to replace/supplement those in current use. The plant kingdom is undoubtedly valuable as a source of new medicinal agents. The present work constitutes a review of the literature on plant extracts and chemically defined molecules of natural origin showing antileishmanial activity. The review refers to 101 plants, their families, and geographical distribution, the parts utilized, the type of extract and the organism tested. It also includes 288 compounds isolated from higher plants and microorganisms, classified into appropriate chemical groups. Some aspects of recent antileishmanial-activity-directed research on natural products are discussed.

Antimicrobial activity of euplotin C, the sesquiterpene taxonomic marker from the marine ciliate Euplotes crassus

Strains of the marine ciliate protist Euplotes crassus produce exclusive terpenoids called euplotins that play an ecological role. Among these derivatives, euplotin C is the main of four secondary metabolites isolated from cultures of this protozoon and represents the sesquiterpene taxonomic marker from E. crassus. Because different terpenoid metabolites of plant origin showed a certain antimicrobial activity, we assessed the compound euplotin C, purified by high-pressure liquid chromatography and solubilized in two solubility enhancers, against the protozoa Leishmania major and Leishmani infantum, the fungus Candida albicans, and nine strains of gram-positive and gram-negative microorganisms. An activity of euplotin C against Leishmania promastigotes was demonstrated (50% lethal doses were 4.6 or 8.1 microg/ml depending on the agent used to solubilize the compound), while the effect was less evident on Candida and nearly absent on bacteria. A nonsignificant cytotoxicity (50% lethal dose, >200 microg/ml) against the J774 cell line was observed. A leishmanicidal activity was also shown by the living, euplotin-producing cells of E. crassus cultured together with promastigotes; this activity increased with time from 10 min to 6 h of incubation. This study provides an initial rationale for the evaluation of euplotin C and other similar natural products as alternative or possibly synergistic compounds for current antiprotozoon chemotherapeutics.

In vitro antiplasmodial activity of extracts and fractions from seven medicinal plants used in the Democratic Republic of Congo

The in vitro antiplasmodial activity of seven EtOH extracts and twenty fractions from the partition of the initial ethanolic extracts from seven African medicinal plants used in the Democratic Republic of Congo (DR Congo) for the treatment of malaria was evaluated. The most active EtOH extracts (IC50 < 3 microg/ml) were those from Cassia occidentalis leaves, Euphorbia hirta whole plant, Garcinia kola stem bark and Phyllanthus niruri whole plant. Their respective petroleum ether soluble fractions also exhibited an antiplasmodial activity with IC50 < 3 microg/ml. EtOH extracts from Vernonia amygdalina leaves (5 < IC50 < 10 microg/ml), Tetracera poggei leaves (10 < IC50 < 50 microg/ml) and Morinda morindoides leaves (50 < IC50 < 100 microg/ml) were less active, but their petroleum ether fractions exhibited a pronounced antiplasmodial activity (IC50 < 3 microg/ml). The same observation could also be made for the petroleum ether fraction from Cassia occidentalis, Euphorbia hirta, Garcinia kola and Phyllanthus niruri. Isoamyl alcohol fractions from Euphorbia hirta, Phyllanthus niruri and Vernonia amygdalina showed IC50) values less than 3 microg/ml, and from Cassia occidentalis, Garcinia kola, Morinda morindoides and Tetracera poggei between 10 and 50 microg/ml. The observed antiplasmodial activity may be related to the presence of terpenes, steroids, coumarins, flavonoids, phenolic acids, lignans, xanthones and anthraquinones.

Antiplasmodial constituents of Cajanus cajan

Bioactivity-guided fractionation of extracts of roots and leaves of Cajanus cajan afforded 8 compounds: betulinic acid, biochanin A, cajanol, genistein and 2'-hydroxygenistein, longistylin A and C, and pinostrobin. The two stilbenes, longistylin A and C, and betulinic acid showed a moderately high in vitro activity against the chloroquine-sensitive Plasmodium falciparum strain 3D7.

Isolation and anti-oomycete activity of nyasol from Anemarrhena asphodeloides rhizomes

The methanol extract of Anemarrhena asphodeloides rhizomes exhibited strong antifungal activity against the plant pathogenic fungi Magnaphothe grisea, Rhizoctonia solani, and the plant pathogenic oomycete Phytophthora capsici. The antifungal substance isolated from the rhizomes of A. asphodeloides was identified to be nyasol, (Z)-1,3-bis(4-hydroxyphenyl)-1,4-pentadiene by NMR and mass spectral analysis. Nyasol effectively inhibited the mycelial growth of Colletotrichum orbiculare, P. capsici, Pythium ultimum, R. solani, and Cladosporium cucumerinum in a range of 1-50 mug/ml, but did not affect the growth of bacteria and yeast. In a greenhouse test, treatment with the antifungal compound nyasol was significantly effective in suppressing the Phytophthora blight on pepper plants.

Natural products as antiparasitic drugs

Natural products are not only the basis for traditional or ethnic medicine. Only recently, they have provided highly successful new drugs such as Artemisinin. Furthermore, screening natural products found in all sorts of environments such as the deep sea, rain forests and hot springs, and produced by all sorts of organisms ranging from bacteria, fungi and plants to protozoa, sponges and invertebrates, is a highly competitive field where all of the major pharmaceutical companies are encountered. Already, many new natural product groups have revealed antiparasitic properties of surprising efficacy and selectivity, as will be shown in this review for plant-derived alkaloids, terpenes and phenolics. Many novel lead structures, however, have severe chemico-physical drawbacks such as poor solubility. Here, innovative drug formulations and carrier systems might help, as discussed by the authors in another article of this series.

Asparosides A and B, two new steroidal saponins from Asparagus meioclados

Asparosides A (1) and B (2), two new saponins, were isolated from the roots of Asparagus meioclados. On the basis of chemical and spectroscopic evidence, their structures were elucidated as 23-O-alpha-arabinopyranosyl-(5beta,25s)-spirostan-3beta,23alpha-diol-3-O-[beta-D-xylopyranosyl(1-->4)]-beta-D-glucopyranoside and 26-O-beta-glucopyranosyl-5beta-furost-20(22)-ene-3beta,26-diol-3-O-[beta-D-xylopyranosyl(1-->4)]-beta-D-glucopyranoside, respectively.

Leishmaniasis phytotherapy. Nature's leadership against an ancient disease

The use of phytotherapy to treat human diseases has its roots in pre-historical times. Despite the modern advances achieved in the field of synthetic chemistry, the most efficient drugs available have their genesis directly or indirectly related with the vegetal kingdom. Indigenous communities have long used plant extracts to treat illnesses. Many of these extracts have shown effective action, with new bioactive compounds being extracted and screened every year. These extracts have also proven to be good sources of therapeutic agents to the treatment of Leishmaniasis. This work highlights some of these agents, while trying to emphasize the importance of plants as a source of new and powerful drugs against this widespread disease.