Browsing by Author "Miyase, T."

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    PublicationOpen Access
    Antimalarial activity of methanolic extracts from plants used in Kenyan ethnomedicine and their interactions with chloroquine (CQ) against a CQ-tolerant rodent parasite, in mice.
    (J Ethnopharmacol, 2007-04-20) Muregi, F. M.; Ishih, A.; Miyase, T.; Suzuki, T.; Kino, H.; Amano, T.; Mkoji, GM; Terada, M
    Methanolic extracts from 15 medicinal plants representing 11 families, used traditionally for malaria treatment in Kenya were screened for their in vivo antimalarial activity in mice against a chloroquine (CQ)-tolerant Plasmodium berghei NK65, either alone or in combination with CQ. The plant parts used ranged from leaves (L), stem bark (SB), root bark (RB), seeds (S) and whole plant (W). When used alone, extracts from seven plants, Clerodendrum myricoides (RB), Ficus sur (L/SB/RB), Maytenus acuminata (L/RB), Rhamnus prinoides (L/RB), Rhamnus staddo (RB), Toddalia asiatica (RB) and Vernonia lasiopus (RB) had statistically significant parasitaemia suppressions of 31.7-59.3%. In combination with CQ, methanolic extracts of Albizia gummifera (SB), Ficus sur (RB), Rhamnus prinoides and Rhamnus staddo (L/RB), Caesalpinia volkensii (L), Maytenus senegalensis (L/RB), Withania somnifera (RB), Ekebergia capensis (L/SB), Toddalia asiatica (L/RB) and Vernonia lasiopus (L/SB/RB) gave statistically significant and improved suppressions which ranged from 45.5 to 85.1%. The fact that these activities were up to five-fold higher than that of extract alone may suggest synergistic interactions. Remarkable parasitaemia suppression by the extracts, either alone or in combination with CQ mostly resulted into longer mouse survival relative to the controls, in some cases by a further 2 weeks. Plants, which showed significant antimalarial activity including Vernonia lasiopus, Toddalia asiatica, Ficus sur, Rhamnus prinoides and Rhamnus staddo warrant further evaluation in the search for novel antimalarial agents against drug-resistant malaria
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    PublicationOpen Access
    In Vivo antimalarial activity of aqueous extracts from Kenyan medicinal plants and their chloroquine (CQ) potentiation effects against a blood-induced CQ-resistant rodent parasite in mice
    (1Department of Parasitology, Hamamatsu University School of Medicine, 1-20-1 Handayama, Hamamatsu 431-3192, Japan. fmuregi@hama-med.ac.jp, 2007-04-21) Muregi, FW; Ishih, A.; Suzuki, T.; Kino, H.; Amano, T.; Mkoji, GM; Miyase, T.; Terada, M
    Hot water extracts from eight medicinal plants representing five families, used for malaria treatment in Kenya were screened for their in vivo antimalarial activity in mice against a chloroquine (CQ) resistant Plasmodium berghei NK65, either alone or in combination with CQ. Extracts of three plants, Toddalia asiatica (root bark), Rhamnus prinoides (leaves and root bark) and Vernonia lasiopus (root bark) showed high chemosuppression in the range 51%-75%. Maytenus acuminata, M. heterophylla, M. senegalensis and Rhamnus staddo had moderate activities of 33%-49% parasitaemia suppression in the root bark and/or leaf extracts, while Withania somnifera (root bark) had a non-significant suppression (21%). In combination with CQ, extracts of V. lasiopus (all parts), leaf extracts of M. senegalensis, R. prinoides and T. asiatica as well as root barks of M. heterophylla, R. staddo and T. asiatica had improved parasitaemia suppression in the range 38%-66%, indicating synergistic interactions. Remarkable parasitaemia suppression by the extracts, either alone or in combination with CQ resulted into longer survival of mice relative to the controls, in some cases by more than 2 weeks. Plants, which showed significant antimalarial activity including V. lasiopus, T. asiatica and R. prinoides, should further be evaluated in the search for novel agents against drug-resistant malaria.
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    PublicationOpen Access
    Possible involvement of IFN-gamma in early mortality of Plasmodium berghei NK65-infected BALB/c mice after febrifugine treatment.
    (Southeast Asian J Trop Med Public Health, 2008) Ishih, A.; Nagata, T.; Kobayashi, F.; Muregi, Francis W.; Ohori, K.; Miyase, T.
    Parasitemia patterns, survival and cytokine levels of Plasmodium berghei NK65-infected BALB/c mice, treated orally with the alkaloidal mixture of febrifugine and isofebrifugine at a dose of 1 mg/kg twice a day for 4 consecutive days were monitored. Whereas the untreated mice showed a progressive increase in parasitemia and ultimate death, the alkaloid mixture-treated group showed a transient suppression of parasitemia during the course of treatment. However, the parasitemia increased on discontinuation of treatment, leading to earlier death of mice in the treated group than in the infected but untreated controls. Mice in the infected but untreated group displayed a significant elevation in serum IFN-gammay levels during the first week post-infection (pI) and from Day 14 pI, relative to the levels in the uninfected controls. In contrast, although mice in the alkaloid mixture-treated group displayed no significant elevation in serum IFN-gamma levels during the first week pI, they showed considerable levels on Day 14 pI. There were no significant differences in serum IL-4 levels among the groups. The titers of the parasite-specific IgG1, IgG2a, IgG2b and IgG3 were significantly elevated from Day 11 pI in both the treated and untreated groups. There was a significant difference in survival duration between the IFN-gamma-/- mutant and BALB/c mice. IFN-gamma-/- mutant mice showed a decrease in parasitemia levels while receiving medication, which was significantly lower than those of the treated BALB/c mice. The results of the present study suggest that although IFN-gamma is significant for protective immunity in mice with malaria infection, it may play an adverse role post-medication, causing earlier mortality of treated BALB/c mice.