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Abacha YZ, Forkuo AD, Gbedema SY, Mittal N, Ottilie S, Rocamora F, Winzeler EA, van Schalkwyk DA, Kelly JM, Taylor MC, Reader J, Birkholtz LM, Lisgarten DR, Cockcroft JK, Lisgarten JN, Palmer RA, Talbert RC, Shnyder SD, Wright CW. Semi-Synthetic Analogues of Cryptolepine as a Potential Source of Sustainable Drugs for the Treatment of Malaria, Human African Trypanosomiasis, and Cancer. Front Pharmacol 2022; 13:875647. [PMID: 35600849 PMCID: PMC9119314 DOI: 10.3389/fphar.2022.875647] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Accepted: 03/08/2022] [Indexed: 12/11/2022] Open
Abstract
The prospect of eradicating malaria continues to be challenging in the face of increasing parasite resistance to antimalarial drugs so that novel antimalarials active against asexual, sexual, and liver-stage malaria parasites are urgently needed. In addition, new antimalarials need to be affordable and available to those most in need and, bearing in mind climate change, should ideally be sustainable. The West African climbing shrub Cryptolepis sanguinolenta is used traditionally for the treatment of malaria; its principal alkaloid, cryptolepine (1), has been shown to have antimalarial properties, and the synthetic analogue 2,7-dibromocryptolepine (2) is of interest as a lead toward new antimalarial agents. Cryptolepine (1) was isolated using a two-step Soxhlet extraction of C. sanguinolenta roots, followed by crystallization (yield 0.8% calculated as a base with respect to the dried roots). Semi-synthetic 7-bromo- (3), 7, 9-dibromo- (4), 7-iodo- (5), and 7, 9-dibromocryptolepine (6) were obtained in excellent yields by reaction of 1 with N-bromo- or N-iodosuccinimide in trifluoroacetic acid as a solvent. All compounds were active against Plasmodia in vitro, but 6 showed the most selective profile with respect to Hep G2 cells: P. falciparum (chloroquine-resistant strain K1), IC50 = 0.25 µM, SI = 113; late stage, gametocytes, IC50 = 2.2 µM, SI = 13; liver stage, P. berghei sporozoites IC50 = 6.13 µM, SI = 4.6. Compounds 3-6 were also active against the emerging zoonotic species P. knowlesi with 5 being the most potent (IC50 = 0.11 µM). In addition, 3-6 potently inhibited T. brucei in vitro at nM concentrations and good selectivity with 6 again being the most selective (IC50 = 59 nM, SI = 478). These compounds were also cytotoxic to wild-type ovarian cancer cells as well as adriamycin-resistant and, except for 5, cisplatin-resistant ovarian cancer cells. In an acute oral toxicity test in mice, 3-6 did not exhibit toxic effects at doses of up to 100 mg/kg/dose × 3 consecutive days. This study demonstrates that C. sanguinolenta may be utilized as a sustainable source of novel compounds that may lead to the development of novel agents for the treatment of malaria, African trypanosomiasis, and cancer.
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Affiliation(s)
- Yabalu Z. Abacha
- School of Pharmacy and Medical Sciences, University of Bradford, Bradford, United Kingdom,Department of Pharmacognosy, Faculty of Pharmacy, University of Maiduguri, Maiduguri, Nigeria
| | - Arnold Donkor Forkuo
- Department of Pharmacology, Faculty of Pharmacy and Pharmaceutical Sciences, College of Health Sciences, Kwame Nkrumah University of Science and Technology (KNUST), Kumasi, Ghana
| | - Stephen Y. Gbedema
- Department of Pharmaceutics, Faculty of Pharmacy and Pharmaceutical Sciences, College of Health Sciences, KNUST, Kumasi, Ghana
| | - Nimisha Mittal
- Malaria Drug Accelerator (MalDA) Consortium, School of Medicine, University of California, San Diego, La Jolla, CA, United States
| | - Sabine Ottilie
- Malaria Drug Accelerator (MalDA) Consortium, School of Medicine, University of California, San Diego, La Jolla, CA, United States
| | - Frances Rocamora
- Malaria Drug Accelerator (MalDA) Consortium, School of Medicine, University of California, San Diego, La Jolla, CA, United States
| | - Elizabeth A. Winzeler
- Malaria Drug Accelerator (MalDA) Consortium, School of Medicine, University of California, San Diego, La Jolla, CA, United States
| | - Donelly A. van Schalkwyk
- Department of Infection Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - John M. Kelly
- Department of Infection Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Martin C. Taylor
- Department of Infection Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Janette Reader
- Department of Biochemistry, Genetics and Microbiology, Faculty of Natural and Agricultural Sciences, Institute for Sustainable Malaria Control, University of Pretoria, Hatfield, South Africa
| | - Lyn-Marie Birkholtz
- Department of Biochemistry, Genetics and Microbiology, Faculty of Natural and Agricultural Sciences, Institute for Sustainable Malaria Control, University of Pretoria, Hatfield, South Africa
| | - David R. Lisgarten
- Biomolecular Research Group, School of Psychology and Life Sciences, Canterbury Christ Church University, Canterbury, United Kingdom
| | - Jeremy K. Cockcroft
- Department of Chemistry, Christopher Ingold Laboratories, University College London, London, United Kingdom
| | | | - Rex A. Palmer
- Department of Crystallography, Biochemical Sciences, Birkbeck College, University of London, London, United Kingdom
| | - Rosemary C. Talbert
- Biomolecular Research Group, School of Psychology and Life Sciences, Canterbury Christ Church University, Canterbury, United Kingdom
| | - Steven D. Shnyder
- School of Pharmacy and Medical Sciences, Institute of Cancer Therapeutics, University of Bradford, Bradford, United Kingdom
| | - Colin W. Wright
- School of Pharmacy and Medical Sciences, University of Bradford, Bradford, United Kingdom,*Correspondence: Colin W. Wright,
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