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Diabetes mellitus is one of the major health problems in Africa. The conventional oral synthetic antidiabetic drugs available to manage the disease are costly and not readily affordable to the majority of the affected population. Interestingly, the continent is endowed with a tremendous number of medicinal plants that have been explored for their folkloric treatment of diabetes mellitus. Scientific investigations have validated the antidiabetic potentials of a number of these medicinal plants but there is no repository with information on these scientifically investigated plants as a guide for future research. In this review article, all of the in vivo antidiabetic studies conducted between January 2000 and July 2013 on African plants are systematically compiled with a closer look at some relevant plants from the continent?s subregions. Plants of the Asteraceae and Lamiaceae families are the most investigated, and West Africa has the highest number of investigated plants. Although promising results were reported in many cases, unfortunately, only a few studies reported the partial characterization of bioactive principles and/or mechanisms of action. It is hoped that government agencies, pharmaceutical industries, and the scientific community will have a look at some of these plants for future research and, if possible, subsequent commercialization.

The ethanol extracts of Syzygium aromaticum flower bud were tested for anti-nociceptive and antiinflammatory effects in mice and Wistar rats which were carried out using acetic acid-induced abdominal contractions in mice and formalin-induced hind paw edema in Wistar rats. Three doses of the ethanol extract (50, 100, and 200mg/kg body weight i.p.) were used for both studies. The extract had an LD 50 of 565.7 mg/kg body weight intraperitoneally in mice. The extracts produced significant effect (P<0.05) at all the three doses. Similarly, the anti-nociceptive activity produced significant effects (P<0.05) at all the three doses of the extract. The result supports the local use of the plant in painful and inflammatory conditions.

Context: The use of Aframomum melegueta K. Schum. (Zingiberaceae) fruit for treatment of diabetes has recently been established in Nigeria. However, compounds responsible for the antidiabetic action have not been identified. Objective: The present study carried out the bioassay-guided isolation of possible bioactive compounds responsible for the antidiabetic action of A. melegueta fruit. Materials and methods: The A. melegueta fruit was sequentially extracted using ethyl acetate (EtOAc), ethanol and water, and the most active extract (EtOAc) was subjected to column chromatography on a silica gel column using solvent gradient systems of hexane (HEX):EtOAc and EtOAc:MeOH and the isolation of compounds was guided by α-glycosidase and α-amylase inhibitory activities at various concentrations (30–240 μg/mL). Results: According to the results, 3 arylalkanes, 6-paradol (1), 6-shogaol (2) and 6-gingerol (3) and a pentacyclic triterpene, oleanolic acid (4) were isolated from A. melegueta fruit. All the compounds exhibited inhibitory effects against α-amylase and α-glucosidase. 6-Gingerol (3) and oleanolic acid (4) showed higher inhibitory activity against α-amylase (IC50: 6-gingerol: 81.78 ± 7.79 μM; oleanolic acid: 91.72 ± 1.63 μM) and α-glucosidase (IC50: 6-gingerol: 21.55 ± 0.45 μM; oleanolic acid: 17.35 ± 0.88 μM) compared to the standard drug, acarbose and other isolated compounds. The kinetics of the enzyme action of the compounds showed a noncompetitive mode of inhibition. Conclusion: The data of this study suggest that the 6-gingerol (3) and oleanolic acid (4) showed higher α-amylase and α-glucosidase inhibitory action and therefore could be responsible for the antidiabetic activity of A. melegueta fruit.

S U M M A R YParasitic infections are among the leading global public health problems with very high economic and mortality burdens. Unfortunately, the available treatment drugs are beset with side effects and continuous parasite drug resistance is being reported. However, new findings reveal more promising compounds especially of plant origin. Among the promising leads are the pentacyclic triterpenes (PTs) made up of the oleanane, ursane, taraxastane, lupane and hopane types. This paper reviews the literature published from 1985 to date on the in vitro and in vivo anti-parasitic potency of this class of phytochemicals. Of the 191 natural and synthetic PT reported, 85 have shown high anti-parasitic activity against various species belonging to the genera of Plasmodium, Leishmania, Trypanosoma, as well as various genera of Nematoda. Moreover, structural modification especially at carbon 3 (C3) and C27 of the parent backbone of PT has led to improved anti-parasitic activity in some cases and loss of activity in others. The potential of this group of compounds as future alternatives in the treatment of parasitic diseases is discussed. It is hoped that the information presented herein will contribute to the full exploration of this promising group of compounds as possible drugs for parasitic diseases.

The aqueous leaves extract of Ocimum gratissimum was investigated for anti-nociceptive and antiinflammatory effects in mice and rats. The models used to study the effect on nociception are the acetic acidinduced abdominal constriction test, hot-plate method in mice. The anti-inflammatory effect was investigated employing the formalin-induced hind-paw oedema in rats. The extract caused a significant (p<0.05), dosedependent inhibition of acetic acid-induced writhing and hot-plate method .The extract also exhibited antiinflammatory effect which was significant (P<0.001) at all the three doses. .The intraperitoneal LD 50 value of the extract was 1264.9mg/kg body weight in mice. Preliminary phytochemical screening revealed the presence of alkaloids, saponins, tannins and flavonoids. The results suggest the extract contained pharmacologically active principles, and supports the local application of the plant in painful and inflammatory conditions.

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