Browsing by Author "Owusu, K.B.-A."
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Item Determination of the absolute configuration of the novel anti-trypanosomal iridoid molucidin isolated from Morinda lucida by X-ray analysis(ELSEVIER, 2015-12) Karasawa, S.; Yoza, K.; Tung, N.H.; Uto, T.; Morinaga, O.; Suzuki, M.; Kwofie, K.D.; Amoa-Bosompem, M.; Boakye, D.A.; Ayi, I.; Adegle, R.; Sakyiamah, M.; Ayertey, F.; Aboagye, F.; Appiah, A.A.; Owusu, K.B.-A.; Tuffour, I.; Atchoglo, P.; Shoyama, Y.The strong anti-trypanosomal active compound, molucidin, contains a spirolactone tetracyclic iridoid skeleton and is isolated from Morinda lucida as an enantiomer of oruwacin, which is isolated from the same plant. To confirm the absolute configuration of molucidin, we prepared single crystals of molucidin for X-ray analysis. The absolute configuration of the afforded single crystal was determined by X-ray crystallography using a Cu radiation source. X-ray diffraction data were collected at 93 K in the 2θ range 7.468–134.99° and analyzed using the SHELXL-2014 program. The corresponding chiral quaternary carbon atoms in molucidin were unambiguously determined as 1R, 5S, 8S, 9S, and 10S. Notably, both enantiomers of a single molecule, molucidin and oruwacin, with a rigid structure have been isolated from the same plant species. The biosynthetic pathway for the formation of molucidin is also discussed on the basis of the absolute configuration. Our results for the first time support for structural elucidation of tetracyclic iridoids using X-ray analysis.Item Extracts of Codiaeum variegatum (L.) A. Juss is Cytotoxic on Human Leukemic, Breast and Prostate Cancer Cell Lines(Open Science Publishers LLP Inc., 2016) Anim, M.T.; Larbie, C.; Appiah-Opong, R.; Tuffour, I.; Owusu, K.B.-A.; Aning, A.Item In Vitro Assessment of Anthelmintic Activities of Rauwolfia vomitoria (Apocynaceae) Stem Bark and Roots against Parasitic Stages of Schistosoma mansoni and Cytotoxic Study(Journal of Parasitology Research, 2017-01) Tekwu, E.W.; Bosompem, K.M.; Anyan, W.K.; Appiah-Opong, R.; Owusu, K.B.-A.; Tettey, M.D.; Kissi, F.A.; Appiah, A.A.; Penlap Beng, V.; Nyarko, A.K.Schistosomiasis is a Neglected Tropical Diseases which can be prevented with mass deworming chemotherapy. The reliance on a single drug, praziquantel, is a motivation for the search of novel antischistosomal compounds. This study investigated the anthelmintic activity of the stem bark and roots of Rauwolfia vomitoria against two life stages of Schistosoma mansoni. Both plant parts were found to be active against cercariae and adult worms. Within 2 h of exposure all cercariae were killed at a concentration range of 62.5-1000 μg/mL and 250-1000 μg/mL of R. vomitoria stem bark and roots, respectively. The LC50 values determined for the stem bark after 1 and 2 h of exposure were 207.4 and 61.18 μg/mL, respectively. All adult worms exposed to the concentrations range of 250-1000 μg/mL for both plant parts died within 120 h of incubation. The cytotoxic effects against HepG2 and Chang liver cell assessed using MTT assay method indicated that both plant extracts which were inhibitory to the proliferation of cell lines with IC50 > 20 μg/mL appear to be safe. This report provides the first evidence of in vitro schistosomicidal potency of R. vomitoria with the stem bark being moderately, but relatively, more active and selective against schistosome parasites. This suggests the presence of promising medicinal constituent(s). © 2017 Emmanuel Mouafo Tekwu et al.Item New anti-trypanosomal active tetracyclic iridoid isolated from Morinda lucida Benth.(Bioorganic & Medicinal Chemistry Letters, 2015-08) Suzuki, M.; Tung, N.H.; Kwofie, K.D.; Adegle, R.; Amoa-Bosompem, M.; Sakyiamah, M.; Ayertey, F.; Owusu, K.B.-A.; Tuffour, I.; Atchoglo, P.; Frempong, K.K.; Anyan, W.K.; Uto, T.; Morinaga, O.; Yamashita, T.; Aboagye, F.; Appiah, A.A.; Appiah-Opong, R.; Nyarko, A.K.; Yamaoka, S.; Yamaguchi, Y.; Edoh, D.; Koram, K.; Ohta, N.; Boakye, D.A.; Ayi, I.; Shoyama, Y.Human African trypanosomiasis (HAT), commonly known as sleeping sickness has remained a serious health problem in many African countries with thousands of new infected cases annually. Chemotherapy, which is the main form of control against HAT has been characterized lately by the viewpoints of toxicity and drug resistance issues. Recently, there have been a lot of emphases on the use of medicinal plants world-wide. Morinda lucida Benth. is one of the most popular medicinal plants widely distributed in Africa and several groups have reported on its anti-protozoa activities. In this study, we have isolated one novel tetracyclic iridoid, named as molucidin, from the CHCl3 fraction of the M. lucida leaves by bioassay-guided fractionation and purification. Molucidin was structurally elucidated by 1H and 13C NMR including HMQC, HMBC, H–H COSY and NOESY resulting in tetracyclic iridoid skeleton, and its absolute configuration was determined. We have further demonstrated that molucidin presented a strong anti-trypanosomal activity, indicating an IC50 value of 1.27 μM. The cytotoxicity study using human normal and cancer cell lines indicated that molucidin exhibited selectivity index (SI) against two normal fibroblasts greater than 4.73. Furthermore, structure–activity relationship (SAR) study was undertaken with molucidin and oregonin, which is identical to anti-trypanosomal active components of Alnus japonica. Overlapping analysis of the lowest energy conformation of molucidin with oregonin suggested a certain similarities of aromatic rings of both oregonin and molucidin. These results contribute to the future drug design studies for HAT.