No abstract

Diabetes mellitus is a public health problem affecting about 8.4% of people in the world and knows an alarming progression in sub-Saharan Africa and in Cameroon precisely. The current therapeutic strategies have prohibitive prices, are unavailable and have harmful side-effects. So, this work aimed at contributing to the valorization of medicinal flora and `knowledge of traditional healers in Foumban, West-Cameroon, in the treatment of diabetes. An ethnopharmacological survey was conducted by consulting traditional healers of the District of Foumban. At the end of this investigation, Phragmanthera capitata, which was found to be the most active plant following preliminary tests, was selected for antidiabetic studies on three groups of rats: normal glycaemia, temporary hyperglycemia and diabetic. The first two groups were treated per os, with aqueous extract of leaves from P. capitata, with the doses of D2 (4 mL/kg) obtained from the traditional healers, D1 (half of D2), D3 (double of D2) and by glibenclamide (2.5 mg/kg). The rats of the last group were treated twice per day, with the same doses of extract and glibenclamide for 13 days and were sacrificed on the 14th day. Their blood was collected by cardiac puncture for the determination of biochemical and hematological parameters. Phytochemical screening was performed using standard methods. The administration of aqueous extract of P. capitata led to a hypoglycaemia effect in normal rats, a reduction of glycaemia in the temporary hyperglycaemia and diabetic rats. In addition, an improvement of lipid assessment, renal and hepatic parameters related to the installation of diabetes, as well as an immune-modulator effect of the extract were noted in diabetic rats treated for 13 days. Phytochemical screening indicated that the extract contains saponins, tannins, flavonoids, steroids and terpens. This work along with findings justifies the traditional use of this plant in the treatment of diabetes mellitus.

Phragmanthera capitata was reported to possess many biological properties making it a good candidate for the formulation of a phytomedicine with multiple effects. In this work, we studied some factors likely to modify these therapeutic properties with the aim to contribute to its standardization as an improved traditional medicine. P. capitata parasitizing Persea americana, Psidium guajava, and Podocarpus mannii were harvested at three phenological stages (vegetative, flowering, and fruiting stages). The extracts were prepared by maceration in n-hexane, ethyl acetate, ethanol, methanol, and distilled water. The total phenolic, flavonoid, flavonol, and tannin contents were measured using appropriate methods. The antioxidant potential of extracts was investigated using TAC, DPPH scavenging, and FRAP methods. The α-amylase and α-glucosidase inhibitory activities of extracts were determined using enzymatic methods. The ethyl acetate extracts with the best phenolic content were subjected to HPLC analysis. The extraction yields were higher with methanol. The ethyl acetate extract of P. capitata harvested from P. guajava showed a stable HPLC profile during the development of the plant, while extracts from the plant collected from P. americana and P. mannii showed both qualitative and quantitative variations according to phonological stages of the plant. The inhibition of α-amylase was more pronounced for P. capitata harvested from P. guajava, decreasing during flowering and fruiting, while inhibition of α-glucosidase was not influenced by the phenological stage and the host of the plant. The α-amylase inhibitors were better extracted by ethyl acetate and those of α-glucosidase by ethanol or methanol. The phenolic contents and antioxidant properties of the extracts were influenced by the phenological stage of P. capitata and its hosts. These results suggest that it is preferable to harvest P. capitata during flowering or during fruiting stages on any host. None of the used solvents permitted an optimal extraction of active principles form P. capitata, suggesting that the mixture of solvents must be considered in further studies.

Phragmanthera capitata is a medicinal plant used in traditional medicine to treat several diseases, including diabetes. Its antioxidant properties and inhibitory effects on enzyme-carbohydrate digestion activities have been demonstrated. The present study aimed to provide data that can contribute to rationalizing the preparation of antioxidant and antidiabetic extracts from this plant. P. capitata (whole plant) growing on Persea americana was harvested at the fruiting stage. A response surface design-type central composite was applied to maximize the extraction yield, phenolic contents, and antioxidant and antidiabetic properties of the ethyl acetate extract of P. capitata. The influencing extraction factors were temperature, powder particle size, and solvent-to-powder ratio. The total phenolic content, total antioxidant capacity (TAC), DPPH scavenging ability, ferric reducing antioxidant power (FRAP), and antidiabetic (α-amylase and α-glucosidase inhibitory) effects of the extracts were determined using conventional methods. A temperature above 55°C contributed to the degradation of the extract, which was reflected in the GC-MS profile by a significant reduction in the number of compounds it contained. The optimal conditions were defined as 24.42°C for temperature, 250 µm powder particle size, and 8.30 (v:w) solvent-to-powder ratio. This extraction protocol resulted in more than twice the extraction yield (3.05%), TTC (62.30 mg TAE/g), TAC (41.41 mg AAE/g), FRAP (186.56 mg AAE/g), and α-amylase (IC50 15.05 µg/mL) and α-glucosidase (IC50 21.14 µg/mL) inhibitory activities compared to our previous results. Additionally, these optimal conditions led experimentally to the extraction of higher phenolic content and to the attainment of higher antioxidant and antidiabetic activity, which closely matched the predicted values. Using these conditions, it is possible to prepare an antidiabetic phytomedicine from P. capitatathat can prevent oxidative stress complications. However, further complementary studies should be carried out considering other factors that influence the composition and pharmacological properties of the extract.