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Herb that enhances efficacy of malaria medicines discovered


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Nigeria

Herb that enhances efficacy of malaria medicines discovered

 

The rainy season is here and so is malaria. Often, people resort to herbal therapies either during, prior to, or after the use of conventional antimalarial drugs in West Africa.  This is understandable because up to 80 per cent of African population use traditional medicine, especially plant remedies, in the management of diseases including malaria.

Malaria is caused by a parasite called Plasmodium, which is transmitted via the bites of infected mosquitoes. In the human body, the parasites multiply in the liver, and then infect red blood cells. Symptoms of malaria include fever, headache, and vomiting, and usually appear between 10 and 15 days after the mosquito bite. If not treated, malaria can quickly become life-threatening by disrupting the blood supply to vital organs.

But very few reports are available on the interaction of herbal anti-malarial products with some of the conventional antimalarial drugs. Also, the use of combination of two or more drugs can have synergism, additive or antagonism effect.

Now, with experts’ increasing interest in the use of a combination of two or more drugs as a way of delaying or overcoming development of drug resistance is topical in malarial chemotherapy research, more studies are on to evaluate the interaction between common herbs used in the management of malaria and some of the conventional antimalarial drugs.

One of such studies is that which evaluated the antimalarial activities of aqueous extract of Khaya grandifoliola plant (African mahogany or Oganwo in Yoruba land) alone and in combination with two commonly available anti-malarial drugs (chloroquine and halofantrine) against rodent malaria parasite in mice.

Aqueous decoction of African mahogany is commonly used by traditional medical practitioners in West Africa in the management of malaria. This plant has been scientifically evaluated for its anti-malarial activity, toxic effects, effects on red blood cells and bone mineral content in rats and on some biochemical parameters in rats.

The stem bark of African mahogany is widely used as decoction by traditional healers in Nigeria. However, some traditional healers soak the stem bark along with some other herbs with diluted ethanol to manage febrile conditions. As such equal volumes of ethanol and water were used by them. Of course, besides, ethanol being an organic solvent, it possesses better extractive capability than water to extract the chemical substances that helps to treat malaria.

The 2010 study documented in the African Journal of Traditional, Complementary and Alternative Medicines, was entitled “Chemotherapeutic interaction between Khaya Grandifoliola stem bark extract and two anti-malarial drugs in mice.” It was carried out by Steve O Ijarotimi; Joseph M Agbedahunsi; Clement O Adewunmi and Cyprian O Onyeji, all researchers at the Obafemi Awolowo University, Ile-Ife, Osun State.

In the study, various doses of ethanol extract of African mahogany stem bark (50–400 mg/kg/day) were administered orally to Swiss albino mice infected with Plasmodium yoelii nigerense. A dose of 100 mg/kg/day of the extract was also combined with 2.5 mg/kg/day of chloroquine or 6.25 mg/kg/day of halofantrine in both early and established malaria infection test models.

All the animals were treated daily for five days and were assessed daily for the five days of treatment. On each day of the assessment, percentage parasitaemia and percentage parasite clearance for each of the mice relative to the control was determined.  After the five days of drug and/or extract administration, the mice were observed till day 28. Any death that occurred during this period was noted and the mean survival time was determined.

The researchers found a dose-dependent suppression of malaria parasite in the animals that had the extract and the standard drugs tested. However, there was an increase in absorption of halofantrine in the tested animals that had both this drug and herb extract.

The results showed that in the early malaria infection test, African mahogany, in combination with chloroquine or halofantrine, elicited enhanced antiplasmodial effect in the established infection, there was significantly greater parasite clearance following the administration of the combination when compared to the effects of African mahogany or the conventional drugs alone.

Interestingly, based on the study, they pointed out that lower therapeutic doses of halofantrine may be required to ensure malaria parasite clearance when used in combination with African mahogany. “This may constitute great advantage to halofantrine which is associated with toxicity to the heart at high doses,” they stated.

They added: “The parasite suppression and clearance for K. grandifoliola/halofantrine combination were significantly higher when compared to the sum of the effect of the extract and halofantrine separately. These observations tend to suggest a synergistic interaction between the extract and halofantrine. “

“On the other hand, the effects of combination of the extract with chloroquine in both infection models were indicative of additive interaction since the effects of the combination were comparable to sum of the separate effects of the extract and chloroquine.”

In response to wide spread multidrug resistance of malaria parasites to monotherapies, the researchers said that the study showed that African mahogany bark extract in combination with halofantrine, which is associated with enhanced efficacy. According to them, the study underscores possible merits in combining conventional antimalarial drugs with herbal remedies.

The combination of Artemisinin derivatives with other antimalarial drugs has become a standard practice in malaria chemotherapy. Antimalarial combination chemotherapy is widely advocated because combination therapies can increase efficacy, shorten duration of treatment and hence improve compliance, in addition to reduction in the risk of resistant parasites arising through mutation during therapy.

Previously in the course of evaluating the contribution of phytomedicine to possible drug discovery of antimalarial drugs, an ethnomedical survey of specialised children’s traditional clinics validated the efficacy of herbal remedies. The herbalists administered eight herbal remedies and Gossypium arboretum (cotton plant), cashew, Citrus medica, Phyllanthus amarus (ehin olobe and eyin olobe in Yoruba or ngwu in Igbo) and Lippia multiflora were the main ingredients in the efficacious remedies.

Another study, aside indicating that boiling in water or alcohol was the most common method used in the preparation of the remedies, found that neem (Azadirachta indica) (87.5 per cent), Mango (75.0 per cent), Morinda lucida or brimstone tree(68.8 per cent) and Citrus medica (68.8 per cent) were four most frequently mentioned plants in the South-west ethnobotany for fevers.

 

 

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Updated 7 Years ago
 

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