A new alkaloid paenidigyamycin A (1) was obtained from the novel Ghanaian Paenibacillus sp. isolated from the mangrove rhizosphere soils of the Pterocarpus santalinoides tree growing in the wetlands of the Digya National Park, Ghana. Compound 1 was isolated on HPLC at t_R = 37.0 min and its structure determined by MS, 1D, and 2D-NMR data. When tested against L. major, 1 (IC₅₀ 0.75 µM) was just as effective as amphotericin B (IC₅₀ 0.31 µM). Against L. donovani, 1 (IC₅₀ 7.02 µM) was twenty-two times less active than amphotericin B (IC₅₀ 0.32 µM), reinforcing the unique effectiveness of 1 against L. major. For T. brucei brucei, 1 (IC₅₀ 0.78 µM) was ten times more active than the laboratory standard Coptis japonica (IC₅₀ 8.20 µM). The IC₅₀ of 9.08 µM for 1 against P. falciparum 3d7 compared to artesunate (IC₅₀ 36 nM) was not strong, but this result suggests the possibility of using the paenidigyamycin scaffold for the development of potent antimalarial drugs. Against cercariae, 1 showed high anticercaricidal activity compared to artesunate. The minimal lethal concentration (MLC) and minimal effective concentration (MEC) of the compound were 25 and 6.25 µM, respectively, while artesunate was needed in higher quantities to produce such results. However, 1 (IC₅₀ > 100 µM) was not active against T. mobilensis.

The plant Zanthoxylum zanthoxyloides (Lam.) Zepern. & Timler is one of the most important medicinal species of the genus Zanthoxylum on the African continent. It is used in the treatment and management of parasitic diseases in sub-Saharan Africa. These properties have inspired scientists to investigate species within the genus for bioactive compounds. However, a study, which details a spectroscopic, spectrometric and bioactivity guided extraction and isolation of antiparasitic compounds from the genus Zanthoxylum is currently non-existent. Tortozanthoxylamide (1), which is a derivative of the known compound armatamide was isolated from Z. zanthoxyloides and the full structure determined using UV, IR, 1D/2D-NMR and high-resolution liquid chromatography tandem mass spectrometry (HRESI-LC-MS) data. When tested against Trypanosoma brucei subsp. brucei, the parasite responsible for animal African trypanosomiasis in sub-Saharan Africa, 1 (IC₅₀ 7.78 µM) was just four times less active than the commercially available drug diminazene aceturate (IC₅₀ 1.88 µM). Diminazene aceturate is a potent drug for the treatment of animal African trypanosomiasis. Tortozanthoxylamide (1) exhibits a significant antitrypanosomal activity through remarkable alteration of the cell cycle in T. brucei subsp. brucei, but it is selectively non-toxic to mouse macrophages RAW 264.7 cell lines. This suggests that 1 may be considered as a scaffold for the further development of natural antitrypanosomal compounds.

The Ghanaian Paenibacillus sp. DE2SH (GenBank Accession Number: MH091697) is a prolific producer of potent antiparasitic alkaloids. Further detailed study of the culture broth of this strain produced the compound Paenidigyamycin G (1), which is a derivative of the known antiparasitic compound Paenidigyamycin A (2). Compound (1) was isolated on HPLC at t_R ≈ 37.5 min and its structure determined by IR, UV, MS, 1D, and 2D-NMR data. Compound 1 produced weak to moderate antileishmanial and antitrypanosomal activity when tested against Leishmania donovani (Laveran and Mesnil) Ross (D10) and Trypanosoma brucei subsp. brucei strain GUTat 3.1 with IC₅₀ = 115.41 and 28.75 μM, respectively. This result is interesting since the parent compound 2 is known to possess consistent and potent antiparasitic activity. However, 1 displayed a promising selectivity profile towards T. brucei subsp. brucei due to its relatively low toxicity against normal mouse macrophages RAW 264.7 cells (SI = 8.70). Given that compound 1 is also the main metabolite found in the hexane fraction of all extracts produced by Paenibacillus sp. DE2SH when it is co-cultured with other bacteria strains, it must possess some unique biological functions which should make it an excellent candidate for further biological activity screening in other bioassays.

Digyaindoleacid A (1) is one of the novel alkaloids produced by the Ghanaian Paenibacillus sp. DE2SH (GenBank Accession Number: MH091697) isolated from the mangrove rhizosphere soils of the Pterocarpus santalinoides tree growing in the wetlands of the Digya National Park, Brong Ahafo Region, Ghana. This compound was isolated on HPLC at t_R ≈ 60 min and its structure determined by MS, 1D, and 2D-NMR data. When tested against Trypanosoma brucei subsp. brucei strain GUTat 3.1, 1 produced a half-maximal inhibitory concentration (IC₅₀) 5.21 μM compared to the standard diminazene aceturate (IC₅₀ = 1.86 μM). In the presence of normal mouse macrophages RAW 264.7, 1 displayed a higher selectivity towards T. brucei subsp. brucei (selectivity indices (SI) = 30.2) with low toxicity. This result is interesting given that the drug diminazene aceturate is considerably toxic and 1 is a natural product isolate. The structure of 1 incorporates the backbone of the amino acid tryptophan which is crucial in the metabolism of Trypanosoma brucei subsp. brucei strain GUTat 3.1. It is possible that 1, could interfere with the normal uptake and metabolism of tryptophan in the parasite. However, 1 (IC₅₀ = 135.41 μM) produced weak antileishmanial activity when tested against Leishmania donovani (Laveran and Mesnil) Ross (D10).

The Mycobacterium sp. BRS2A-AR2 is an endophyte of the mangrove plant Rhizophora racemosa G. Mey., which grows along the banks of the River Butre, in the Western Region of Ghana. Chemical profiling using ¹H-NMR and HRESI-LC-MS of fermentation extracts produced by the strain led to the isolation of the new compound, α-d-Glucopyranosyl-(1→2)-[6-O-(l-tryptophanyl)-β-d–fructofuranoside] or simply tortomycoglycoside (1). Compound 1 is an aminoglycoside consisting of a tryptophan moiety esterified to a disaccharide made up of β-d-fructofuranose and α-d-glucopyranose sugars. The full structure of 1 was determined using UV, IR, 1D, 2D-NMR and HRESI-LC-MS data. When tested against Trypanosoma brucei subsp. brucei, the parasite responsible for Human African Trypanosomiasis in sub-Saharan Africa, 1 (IC₅₀ 11.25 µM) was just as effective as Coptis japonica (Thunb.) Makino. (IC₅₀ 8.20 µM). The extract of Coptis japonica (Thunb.) Makino. is routinely used as laboratory standard due to its powerful antitrypanosomal activity. It is possible that, compound 1 interferes with the normal uptake and metabolism of tryptophan in the T. brucei subsp. brucei parasite.

Brain infection by the pathogenic free-living amoebae Naegleria fowleri is a life-threatening illness, with a mortality rate >95% in the US. One of the challenges faced in treating these infections is the lack of efficacious drugs. Here, we further characterize two leads. The first, a N. fowleri enolase inhibitor (HEX ((1-hydroxy-2-oxopiperidin-3-yl) phosphonic acid)), emerged from a target-based approach while the other, BDGR-20191 (rac-(4aR,13bS)-10,11-dichloro-4-(oxetan-3-ylmethyl)-1,2,3,4,4a,5,6,13b-octahydro-8H-[1,6]naphthyridino[5,6-b]quinazolin-8-one), was identified in a phenotypic screen for anti-amoebic agents. Chronic low dose exposure to these agents led to cell lines that were tolerant to each. However, the tolerance phenotypes were reversed in the absence of selection with the agent. Differential gene expression analyses suggest that HEX tolerant cells upregulate cellular components that could impact levels of accumulated glycolytic intermediates, while BDGR-20191 tolerant cells could be targeting membrane biosynthesis. Unbiased metabolomics of the lines supported these possibilities. While HEX and BDGR-20191 are not synergistic with one another or with other standard-of-care drugs, their additive nature suggests they could be a useful addition to current therapeutic cocktails.