An ethnopharmacological survey of medicinal plants traditionally used by the BaKalanga people of the Tutume subdistrict in Central Botswana to manage HIV/AIDS, HIV-associated conditions, and other health conditions

ETHNOPHARMACOLOGICAL RELEVANCE

While access to antiretroviral therapy (ART) continues to improve worldwide, HIV infection and AIDS persist as serious health challenges, particularly in sub-Saharan Africa. Complementary and Alternative Medicines (CAM), as part of indigenous and pluralistic medical systems, are important contributors to primary health care worldwide. However, this knowledge remains relatively undocumented in many parts of sub-Saharan Africa such as the Tutume subdistrict of Central Botswana, where CAM is widely used including potentially for HIV/AIDS and HIV-associated conditions.

AIM OF THE STUDY

To explore the extent to which CAM is used by the BaKalanga Peoples of the Tutume subdistrict, we performed an exploratory community-based project to record medicinal plant use from this relatively undocumented region, with a particular focus on species used for management of HIV/AIDS and HIV-associated conditions.

MATERIALS AND METHODS

Using the snowball sampling technique, we recruited 13 Traditional Health Practitioners (THPs) and conducted in-depth interviews to explore medicinal plant uses and treatment regimens. Plant specimens were collected and bio-authenticated.

RESULTS

We documented 83 plant species used as CAM to treat or manage a variety of conditions including HIV/AIDS, HIV-associated conditions, and other health conditions. Plants from the family Leguminosae were most frequently reported, comprising 21 species (25.3%), followed by 5 from both Euphorbiaceae and Combretaceae families (6.0%). Four plants (4.8%) were used specifically to manage HIV (Lannea edulis (Sond.) Engl. root, Aloe zebrina Baker root, Myrothamnus flabellifolia Welw. whole plant, and Harpagophytum procumbens var. subulobatum (Engl.) tuber), while an additional 7 (8.4%) were reported specifically for treating combinations of HIV-related symptoms. Notably, 25 (30.1%) have not been reported previously as CAM and/or lack reported bioactivity data.

CONCLUSIONS

To our knowledge, this is the first detailed ethnobotanical survey of CAM used by the BaKalanga Peoples of the Tutume subdistrict to manage HIV/AIDS and HIV-associated and other health conditions.

Medicinal Plant Preparations Administered by Botswana Traditional Health Practitioners for Treatment of Worm Infections Show Anthelmintic Activities

Schistosomiasis and soil-transmitted helminths are some of the priority neglected tropical diseases (NTDs) targeted for elimination by the World Health Organization (WHO). They are prevalent in Botswana and although Botswana has begun mass drug administration with the hope of eliminating soil-transmitted helminths as a public health problem, the prevalence of schistosomiasis does not meet the threshold required to warrant large-scale interventions. Although Botswana has a modern healthcare system, many people in Botswana rely on traditional medicine to treat worm infections and schistosomiasis. In this study, ten plant species used by traditional health practitioners against worm infections were collected and tested against Ancylostoma ceylanicum (zoonotic hookworm), Heligmosomoides polygyrus (roundworm of rodents), Necator americanus (New World hookworm), Schistosoma mansoni (blood fluke) [adult and newly transformed schistosomula (NTS)], Strongyloides ratti (threadworm) and Trichuris muris (nematode parasite of mice) in vitro. Extracts of two plants, Laphangium luteoalbum and Commiphora pyaracanthoides, displayed promising anthelmintic activity against NTS and adult S. mansoni, respectively. L. luteoalbum displayed 85.4% activity at 1 μg/mL against NTS, while C. pyracanthoides displayed 78.5% activity against adult S. mansoni at 10 μg/mL.

Safety evaluation and bioassay-guided isolation of antimycobacterial compounds from Morella salicifolia root ethanolic extract

ETHNOPHARMACOLOGICAL RELEVANCE

Although the available medicines can cure almost all tuberculosis drug-susceptible patients some problems including the emergence of multi-drug resistant and extensively drug-resistant strains press for the need of new anti-TB medicines. Morella salicifolia is a common plant that is widely used in traditional medicine for managing HIV and AIDS-related conditions including tuberculosis but no studies have been done to evaluate its safety and efficacy.

AIM OF THE STUDY

This study was designed to investigate the antimycobacterial activity and safety of M. salicifolia extract and its constituents.

MATERIAL AND METHODS

Antimycobacterial activity of the crude extract was tested against non-pathogenic mycobacteria including Mycobacterium aurum (MA), Mycobacterium indicus pranii (MIP) and Mycobacterium madagascariense (MM) using the broth microdilution method. Bioassay-guided fractionation was employed to isolate the active compounds. Some of the isolated active compounds were tested for antimycobacterial activity against the standard and selected clinical isolates of M. tuberculosis. Safety of the crude extract was assessed using cytotoxicity assay and oral acute toxicity testing.

RESULTS

The crude extract exhibited antimycobacterial activity against all the species used. The study led to isolation of six compounds; four pentacyclic triterpenoids; (3β)-3-Hydroxyolean-12-en-28-oic acid (Oleanolic acid) (1), (2α,3β)-2,3-Dihydroxyolean-12-en-28-oic acid (maslinic acid) (2), D-Friedoolean-14-ene-3β,28-diol (taraxerol) (3), and D-Friedoolean-14-en-3β-ol (myricadiol) (4), and two diarylheptanoids; (±)-myricanol (5) and myricanone (6). The six compounds exhibited activity against three nonpathogenic mycobacteria species. Compound 2, was the most active, with MICs of 17, 28 and 56 μg/ml against MM, standard a M. tuberculosis strain H₃₇RV and rifampicin resistant M. tuberculosis clinical isolates, respectively. The crude extract did not show toxicity on peripheral blood mononuclear cells and it was safe in mice following acute oral toxicity test.

CONCLUSION

The results from this study indicate that some isolated compounds in Morella salicifolia could form potential scaffolds for drug development efforts targeting M. tuberculosis. More studies are needed to further explore the potential of the plant extract and its secondary metabolites in the management of HIV and AIDS-related conditions using in-vivo models.

Anthelmintic Activity and Cytotoxic Effects of Compounds Isolated from the Fruits of Ozoroa insignis Del. (Anacardiaceae)

Ozoroa insignis Del. is an ethnobotanical plant widely used in traditional medicine for various ailments, including schistosomiasis, tapeworm, and hookworm infections. From the so far not investigated fruits of Ozoroa insignis, the anthelmintic principles could be isolated through bioassay-guided isolation using Caenorhabditis elegans and identified by NMR spectroscopic analysis and mass spectrometric studies. Isolated 6-[8(Z)-pentadecenyl] anacardic (1), 6-[10(Z)-heptadecenyl] anacardic acid (2), and 3-[7(Z)-pentadecenyl] phenol (3) were evaluated against the 5 parasitic organisms Schistosoma mansoni (adult and newly transformed schistosomula), Strongyloides ratti, Heligmosomoides polygyrus, Necator americanus, and Ancylostoma ceylanicum, which mainly infect humans and other mammals. Compounds 1-3 showed good activity against Schistosoma mansoni, with compound 1 showing the best activity against newly transformed schistosomula with 50% activity at 1µM. The isolated compounds were also evaluated for their cytotoxic properties against PC-3 (human prostate adenocarcinoma) and HT-29 (human colorectal adenocarcinoma) cell lines, whereby compounds 2 and 3 showed antiproliferative activity in both cancer cell lines, while compound 1 exhibited antiproliferative activity only on PC-3 cells. With an IC50 value of 43.2 µM, compound 3 was found to be the most active of the 3 investigated compounds.

The African natural product knipholone anthrone and its analogue anthralin (dithranol) enhance HIV-1 latency reversal

A sterilizing or functional cure for HIV is currently precluded by resting CD4⁺ T cells that harbor latent but replication-competent provirus. The "shock-and-kill" pharmacological ap-proach aims to reactivate provirus expression in the presence of antiretroviral therapy and target virus-expressing cells for elimination. However, no latency reversal agent (LRA) to date effectively clears viral reservoirs in humans, suggesting a need for new LRAs and LRA combinations. Here, we screened 216 compounds from the pan-African Natural Product Library and identified knipholone anthrone (KA) and its basic building block anthralin (dithranol) as novel LRAs that reverse viral latency at low micromolar concentrations in multiple cell lines. Neither agent's activity depends on protein kinase C; nor do they inhibit class I/II histone deacetylases. However, they are differentially modulated by oxidative stress and metal ions and induce distinct patterns of global gene expression from established LRAs. When applied in combination, both KA and anthralin synergize with LRAs representing multiple functional classes. Finally, KA induces both HIV RNA and protein in primary cells from HIV-infected donors. Taken together, we describe two novel LRAs that enhance the activities of multiple "shock-and-kill" agents, which in turn may inform ongoing LRA combination therapy efforts.

Biological activity and stability analyses of knipholone anthrone, a phenyl anthraquinone derivative isolated from Kniphofia foliosa Hochst

Knipholone (1) and knipholone anthrone (2), isolated from the Ethiopian medicinal plant Kniphofia foliosa Hochst. are two phenyl anthraquinone derivatives, a compound class known for biological activity. In the present study, we describe the activity of both 1 and 2 in several biological assays including cytotoxicity against four human cell lines (Jurkat, HEK293, SH-SY5Y and HT-29), antiplasmodial activity against Plasmodium falciparum 3D7 strain, anthelmintic activity against the model organism Caenorhabditis elegans, antibacterial activity against Aliivibrio fischeri and Mycobacterium tuberculosis and anti-HIV-1 activity in peripheral blood mononuclear cells (PBMCs) infected with HIV-1_c. In parallel, we investigated the stability of knipholone (2) in solution and in culture media. Compound 1 displays strong cytotoxicity against Jurkat, HEK293 and SH-SY5Y cells with growth inhibition ranging from approximately 62-95% when added to cells at 50 μM, whereas KA (2) exhibits weak to strong activity with 26, 48 and 70% inhibition of cell growth, respectively. Both 1 and 2 possess significant antiplasmodial activity against Plasmodium falciparum 3D7 strain with IC₅₀ values of 1.9 and 0.7 μM, respectively. These results complement previously reported data on the cytotoxicity and antiplasmodial activity of 1 and 2. Furthermore, compound 2 showed HIV-1_c replication inhibition (growth inhibition higher than 60% at tested concentrations 0.5, 5, 15 and 50 μg/ml and an EC₅₀ value of 4.3 μM) associated with cytotoxicity against uninfected PBMCs. The stability study based on preincubation, HPLC and APCI-MS (atmospheric-pressure chemical ionization mass spectrometry) analysis indicates that compound 2 is unstable in culture media and readily oxidizes to form compound 1. Therefore, the biological activity attributed to 2 might be influenced by its degradation products in media including 1 and other possible dimers. Hence, bioactivity results previously reported from this compound should be taken with caution and checked if they differ from those of its degradation products. To the best of our knowledge, this is the first report on the anti-HIV activity and stability analysis of compound 2.

Cytotoxicity of epunctanone and four other phytochemicals isolated from the medicinal plants Garcinia epunctata and Ptycholobium contortum towards multi-factorial drug resistant cancer cells

INTRODUCTION

Resistance of cancer cells is a serious impediment to chemotherapy and several phytochemicals are active against multi-drug resistant (MDR) phenotypes. The cytotoxicity of five naturally occurring compounds: betulin (1), mundulea lactone (2), seputhecarpan A (3), seputheisoflavone (4) and epunctanone (5) was evaluated on a panel of 9 cancer cell lines including various sensitive and drug-resistant cell lines. The modes of action of compound 5 were further investigated.

METHODS

The resazurin reduction assay was used to evaluate cytotoxicity of samples and ferroptotic cell death induced by compound 5; caspase-Glo assay was used to detect the activation of caspases in CCRF-CEM leukemia cells treated with compound 5. Flow cytometry was used for cell cycle analysis in CCRF-CEM cells treated with compound 5, as well as detection of apoptotic cells by annexin V/PI staining, analysis of mitochondrial membrane potential (MMP) and measurement of reactive oxygen species (ROS).

RESULTS

Compounds 1-5 displayed cytotoxic effects in the 9 studied cancer cell lines with IC₅₀ values below 70 µM. The IC₅₀ values varied from 8.20 µM (in HCT116 (p53^-/-) colon cancer cells) to 35.10 µM (against HepG2 hepatocarcinoma cells) for 1, from 8.84 µM (in CEM/ADR5000 leukemia cells) to 48.99 µM (in MDA-MB-231 breast adenocarcinoma cells) for 2, from 12.17 µM (in CEM/ADR5000 cells) to 65.08 µM (in MDA-MB-231 cells) for 3, from 23.80 µM (in U87MG.ΔEGFR glioblastoma cells) to 68.66 µM (in HCT116 (p53^-/-) cells) for 4, from 4.84 µM (in HCT116 (p53^-/-) cells) to 13.12 µM (in HepG2 cells) for 5 and from 0.02 µM (against CCRF-CEM cells) to 122.96 µM (in CEM/ADR5000 cells) for doxorubicin. Compound 5 induced apoptosis in CCRF-CEM cells through alteration of MMP and increase in ROS production. In addition to apoptosis, ferroptosis was also identified as another mode of cell death induced by epunctanone.

CONCLUSIONS

Compounds 1-5 are valuable cytotoxic compounds that could be used to combat MDR cancer cells. Benzophenoe 5 is the most active molecule and deserve more investigations to develop new anticancer drugs.

The Croton megalobotrys Müll Arg. traditional medicine in HIV/AIDS management: Documentation of patient use, in vitro activation of latent HIV-1 provirus, and isolation of active phorbol esters

ETHNOPHARMACOLOGICAL RELEVANCE

Current HIV therapies do not act on latent cellular HIV reservoirs; hence they are not curative. While experimental latency reversal agents (LRAs) can promote HIV expression in these cells, thereby exposing them to immune recognition, existing LRAs exhibit limited clinical efficacy and high toxicity. We previously described a traditional 3-step medicinal plant regimen used for HIV/AIDS management in Northern Botswana that inhibits HIV replication in vitro. Here we describe use of one component of the regimen that additionally contains novel phorbol esters possessing HIV latency-reversal properties.

AIM OF THE STUDY

We sought to document experiences of traditional medicine users, assess the ability of traditional medicine components to reverse HIV latency in vitro, and identify pure compounds that conferred these activities.

MATERIALS AND METHODS

Experiences of two HIV-positive traditional medicine users (patients) were documented using qualitative interview techniques. Latency reversal activity was assessed using a cell-based model (J-Lat, clone 9.2). Crude plant extracts were fractionated by open column chromatography and reverse-phase HPLC. Compound structures were elucidated using NMR spectroscopy and mass spectrometry.

RESULTS

Patients using the 3-step regimen reported improved health over several years despite no reported use of standard HIV therapies. Crude extracts from Croton megalobotrys Müll Arg. ("Mukungulu"), the third component of the 3-step regimen, induced HIV expression in J-lat cells to levels comparable to the known LRA prostratin. Co-incubation with known LRAs and pharmacological inhibitors indicated that the active agent(s) in C. megalobotrys were likely to be protein kinase C (PKC) activator(s). Consistent with these results, two novel phorbol esters (Namushen 1 and 2) were isolated as abundant components of C. megalobotrys and were sufficient to confer HIV latency reversal in vitro.

CONCLUSION

We have identified novel LRAs of the phorbol ester class from a medicinal plant used in HIV/AIDS management. These data, combined with self-reported health effects and previously-described in vitro anti-HIV activities of this traditional 3-step regimen, support the utility of longitudinal observational studies of patients undergoing this regimen to quantify its effects on plasma viral loads and HIV reservoir size in vivo.

Cytotoxicity of seputhecarpan D, thonningiol and 12 other phytochemicals from African flora towards human carcinoma cells

Background

Despite the remarkable progress in cancer therapy in recent years, this disease still remains a serious public health concern. The use of natural products has been and continues to be one of the most effective ways to fight malignancies. The cytotoxicity of 14 compounds from African medicinal plants was evaluated in four human carcinoma cell lines and normal fibroblasts. The tested samples included: β-spinasterol (1), friedelanone (2), 16β-hydroxylupeol (3), β-amyrin acetate (4), lupeol acetate (5), sequoyitol (6), rhamnitrin (7), europetin 3-O-rhamnoside (8), thonningiol (9), glyasperin F (10), seputhecarpan B (11), seputhecarpan C (12), seputhecarpan D (13) and rheediaxanthone A (14).

Methods

The neutral red uptake (NR) assay was used to evaluate the cytotoxicity of samples; caspase-Glo assay, flow cytometry for cell cycle analysis and mitochondrial membrane potential (MMP) as well as spectrophotometry to measure levels of reactive oxygen species (ROS) were performed to detect the mode of action of compounds 9 and 13 in MCF-7 breast adenocarcinoma cells.

Results

Compounds 3, 9–13 displayed cytotoxic effects against the four tested cancer cell lines with IC₅₀ values below 85 μM. Compounds 9 and 13 had IC₅₀ values below 10 μM in 4/4 and 3/4 tested cell lines respectively. The IC₅₀ values varied from 0.36 μM (against MCF7 cells) to 5.65 μM (towards colon carcinoma DLD-1 cells) for 9, from 9.78 μM (against MCF7 cells) to 67.68 μM (against HepG2 cells) for 13 and 0.18 μM (towards HepG2 cells) to 72 μM (towards Caco-2 cells) for the reference drug, doxorubicin. Compounds 9 and 13 induced cell cycle arrest in Go/G1 whilst doxorubicin induced arrest in G2/M. The two molecules (9 and 13) also induced apoptosis in MCF-7 cells through activation of caspases 3/7 and 9 as well as enhanced ROS production.

Conclusion

Compounds 9 and 13 are good cytotoxic phytochemicals that should be explored more in future to develop a cytotoxic drug to fight human carcinoma.

Electronic supplementary material

The online version of this article (10.1186/s12906-018-2109-9) contains supplementary material, which is available to authorized users.

Two new pterocarpans and a new pyrone derivative with cytotoxic activities from Ptycholobium contortum (N.E.Br.) Brummitt (Leguminosae): revised NMR assignment of mundulea lactone

BACKGROUND

Ptycholobium is a genus related to Tephrosia which comprises only three species. Compared to Tephrosia, which has been phytochemically and pharmacologically studied, Ptycholobium species have only few or no reports on their chemical constituents. Moreover, no studies on the cytotoxic activities of its secondary metabolites have been previously documented.

RESULTS

From the non polar fractions of the roots bark of Ptycholobium contortum (syn Tephrosia contorta), two new pterocarpans: seputhecarpan C 1 and seputhecarpan D 2 and a new pyrone derivative, ptycholopyrone A 3 were isolated. Alongside, five known compounds identified as 3-α,α-dimethylallyl-4-methoxy-6-styryl-α-pyrone or mundulea lactone 4, glyasperin F 5, seputhecarpan A 6, seputheisoflavone 7 and 5-O-methyl-myo-inositol or sequoyitol 8 were also obtained. Their structures were established by the mean means of spectroscopic data in conjunction to those reported in literature. The NMR assignment of the major compound mundulea lactone 4 is revised in this paper. In addition, the cytotoxicity of the isolated metabolites was evaluated on two lung cancer cell lines A549 and SPC212. 8 was not active while compounds 1, 2, 4-7 displayed antiproliferative effects against the two carcinoma cell lines with IC₅₀ values below 75 µM. IC₅₀ values below 10 µM were obtained for 4, 6 and 7 on SPC212 cells.

CONCLUSION

Based on the obtained results, Ptycholobium contortum turns to be a rich source of phenolic metabolites among them some bearing prenyl moieties. This study reports for the first time the isolation of pyrone derivatives 3 and 4 from Ptycholobium genus. The cytotoxicity observed for the isolate is also reported for the first time and shows that 4, 6 and 7 could be chemically explored in order to develop a hit candidate against lung cancer. Graphical abstractTwo new pterocarpans and a new pyrone derivative with cytotoxic activities from ptycholobium contortum (N.E.Br.) Brummitt (Leguminosae): revised NMR assignment of mundulea lactone.

Screening of the Pan-African natural product library identifies ixoratannin A-2 and boldine as novel HIV-1 inhibitors

The continued burden of HIV in resource-limited regions such as parts of sub-Saharan Africa, combined with adverse effects and potential risks of resistance to existing antiretroviral therapies, emphasize the need to identify new HIV inhibitors. Here we performed a virtual screen of molecules from the pan-African Natural Product Library, the largest collection of medicinal plant-derived pure compounds on the African continent. We identified eight molecules with structural similarity to reported interactors of Vpu, an HIV-1 accessory protein with reported ion channel activity. Using in vitro HIV-1 replication assays with a CD4+ T cell line and peripheral blood mononuclear cells, we confirmed antiviral activity and minimal cytotoxicity for two compounds, ixoratannin A-2 and boldine. Notably, ixoratannin A-2 retained inhibitory activity against recombinant HIV-1 strains encoding patient-derived mutations that confer resistance to protease, non-nucleoside reverse transcriptase, or integrase inhibitors. Moreover, ixoratannin A-2 was less effective at inhibiting replication of HIV-1 lacking Vpu, supporting this protein as a possible direct or indirect target. In contrast, boldine was less effective against a protease inhibitor-resistant HIV-1 strain. Both ixoratannin A-2 and boldine also inhibited in vitro replication of hepatitis C virus (HCV). However, BIT-225, a previously-reported Vpu inhibitor, demonstrated antiviral activity but also cytotoxicity in HIV-1 and HCV replication assays. Our work identifies pure compounds derived from African plants with potential novel activities against viruses that disproportionately afflict resource-limited regions of the world.

Old plants newly discovered: Cassia sieberiana D.C. and Cassia abbreviata Oliv. Oliv. root extracts inhibit in vitro HIV-1c replication in peripheral blood mononuclear cells (PBMCs) by different modes of action

ETHNOPHARMACOLOGICAL RELEVANCE

Despite advances in anti-retroviral therapy which has transformed HIV/AIDS from a fatal to a manageable chronic disease, increasing viral drug resistance, side effects and uneven access to anti-retroviral drugs remain considerable therapeutic challenges. Partly as a consequence of these shortcomings and partly based on the fact that HIV/AIDS gives rise to opportunistic infections whose symptoms have been managed in Africa in an HIV/AIDS-independent context by traditional healers for centuries, many HIV/AIDS patients use herbal medicines. The aim of this study was to screen selected medicinal plants from Botswana, used by traditional healers to treat/manage HIV/AIDS, for inhibitory activities on HIV replication.

MATERIALS AND METHODS

Based on an ethnomedical survey, ethanolic tannin-containing and tannin-free extracts from 10 medicinal plants were tested for inhibitory properties against a clone of HIV-1c (MJ(4)) measuring cytopathic effect protection and levels of viral p24 antigen in infected PBMCs.

RESULTS

Cassia sieberiana D.C., Cassia abbreviata Oliv. Oliv. and Plumbago zeylanica L. extracts showed significant inhibition of HIV-1c (MJ(4)) replication. The inhibitory activity of the Plumbago zeylanica extract could be attributed to its tannin content. Anti-HIV activity of Cassia sieberiana root and bark extracts, and Cassia abbreviata root extracts occurred in a concentration-dependent manner with an effective concentration (EC(50)) of 65.1μg/ml, 85.3μg/ml and 102.8μg/ml, respectively. Experiments to elucidate possible mechanism(s) of action revealed that Cassia sieberiana root and bark extracts blocked HIV replication at its binding- (EC(50)=70.2μg/ml and 90.8μg/ml, respectively) and entry stage (EC(50)=88.9μg/ml and 100.5μg/ml, respectively) while Cassia abbreviata extracts did not.

CONCLUSIONS

We report here for the first time a direct inhibitory effect on HIV-1c replication of extracts from two extremely popular medicinal plants, Cassia sieberiana and Cassia abbreviata. Considering the traditional uses of both Cassia species, our findings strongly suggest pilot clinical observational studies involving traditional healers to further evaluate the therapeutic potential of the Cassia extracts.