In vivo antiplasmodial potentials of the combinations of four nigerian antimalarial plants.

Various combinations of Nauclea latifolia root, Artocarpus altilis stem bark, Murraya koenigii leaf and Enantia chlorantha stem bark used in African ethnomedicine as decoctions for malaria and fevers, and combinations with standard drugs, were investigated for antiplasmodial activities using Plasmodium berghei berghei-infected mice. The respective prophylactic and curative ED50 values of 189.4 and 174.5 mg/kg for N. latifolia and chemosuppressive ED50 value of 227.2 mg/kg for A. altilis showed that they were the best antimalarial herbal drugs. A 1.6-fold increase of the survival time given by the negative control was elicited by M. koenigii, thereby confirming its curative activity. Pyrimethamine with an ED50 of 0.5 ± 0.1 mg/kg for the prophylactic, and chloroquine with ED50 = 2.2 ± 0.1 and 2.2 ± 0.0 mg/kg for the chemosuppressive and curative tests, respectively, were significantly (p < 0.05) more active. Co-administrations of N. latifolia with the standard drugs significantly reduced their prophylactic, chemosuppressive and curative actions, possibly increasing the parasites' resistance. Binary combinations of N. latifolia or M. koenigii with any of the other plants significantly increased the prophylactic and suppressive activities of their individual plants, respectively. Also, E. chlorantha with A. altilis or N. latifolia enhanced their respective prophylactic or curative activities, making these combinations most beneficial against malaria infections. Combinations of three and four extracts gave varied activities. Hence, the results justified the combinations of ethnomedicinal plants in antimalarial herbal remedies and showed the importance of the three in vivo models in establishing antimalarial activity.

Influence of formulation ratio of the plant components on the antimalarial properties of MAMA decoction.

Mangifera indica, Alstonia boonei, Morinda lucida and Azadirachta indica (MAMA) decoction, commonly prepared and used in Nigeria from 1:1:1:1 ratio of Mangifera indica L. (Anacardiaceae), Alstonia boonei De Wild (Apocynaceae), Morinda lucida Benth (Rubiaceae), and Azadirachta indica A. Juss (Meliaceae) leaves, plus four new variants of this combination were subjected to three in vivo antimalarial test models using chloroquine-sensitive Plasmodium berghei berghei to determine the most active under each of the test models. Using the original formulation, MAMA (1:1:1:1) which gave ED50 and ED90 of 101.54±2.95 and 227.18±2.95, respectively, as reference for comparison, MAMA-1 (1:2:2:2), with 79.58±1.30 and 170.98±1.30, gave significantly (p<0.05) higher survival at 85 and 340 mg/kg when 80 % of the mice survived for 15.6 and 17.8 days, respectively, while MAMA-2 (2:1:2:2), with 83.57±1.93 and 164.23±1.93, gave comparable survival except at 170 mg/kg with 60 % survivors for 12 days. MAMA-1 and MAMA-2 were the best curative formulations with MAMA-1 giving additional prophylactic activity. MAMA-3 (2:2:2:1) with 98.70±0.91 and 220.17±0.91, gave comparable (p>0.05) survival at 85 mg/kg with 60 % survival for 13.2 days and significantly higher survival at 42.5 mg/kg for 17 days with 40 % survival. Both MAMA and MAMA-3 were the best chemosuppressive formulations plus additional curative activities. MAMA-4 (1:1:2:2), the best prophylactic formulation with 94.87±2.43 and 201.20±2.43 gave significantly higher (p<0.05) survival at all doses except at 21.25 mg/kg which gave 60 % survival up to 10 days. Thus, the antimalarial therapy desired, following appropriate diagnosis, whether prophylactic, chemosuppressive or curative would determine which of the MAMA decoction formulations to be prescribed. This phenomenon of formulary optimization may also be applied to other pharmacological activities.

Evaluation of ethnomedical claim III: anti-hyperglycemic activities of Gongronema latifolium root and stem.

BACKGROUND: The insulinotropic activity of the combined root and stem of Gongronema latifolium (Asclepiadaceae) was evaluated to justify its African ethnomedicinal use in the management of diabetes. METHODS: A methanolic extract and its chromatographic fractions (A1 -A6 ) were tested for glucose-reducing and in vitro insulin-stimulating abilities using glucose-loaded rats and INS-1 cells, respectively. In vivo insulin-releasing activities for the significantly (P<0.05) active antihyperglycemic A5 and A6 and in vitro insulinotropic activity of the C1 fraction and its isolated constituents were also similarly determined. RESULTS: The extract (100 mg/kg) had higher in vivo antihyperglycemic activity than the individual A1 -A6 , indicating a synergistic effect of the plant constituents. Higher in vivo insulin release in response to A5 (100 mg/kg) than A6 , agreed with their in vivo antihyperglycemic activities and confirmed insulin release as a mechanism of action of the plant. Compared with 5.6 mmol/L glucose (negative control), the extract and the A3 , A6 , and C1 (all at 100.0 µg/mL) elicited significantly higher in vitro insulin release that was similar to that of glibenclamide (1.0 µg/mL; P>0.05). Fraction C1 yielded a 1:1 mixture of α-amyrin and ß-amyrin cinnamates (1a:1b), lupenyl cinnamate (2), lupenyl acetate (3), and two unidentified triterpenoids, Y and Z. The 1a:1b mixture (100.0 µg/mL) demonstrated the highest insulinotropic activity that was comparable (P>0.05) to that of glibenclamide (1.0 µg/mL). CONCLUSIONS: The results confirm pancreatic activity as a mechanism underlying the antidiabetic action of G. latifolium and justify its ethnomedical use.