17-Norpimaranes and (9ßH)-17-Norpimaranes from the Tuber of Icacina trichantha.

Seven new 17-norpimarane and (9ßH)-17-norpimarane diterpenoids, icacinlactones A-G (1-7), were isolated from the tuber of Icacina trichantha. The structures were elucidated by spectroscopic and HRMS techniques, and the absolute configuration of 2 was determined by means of X-ray crystallographic analysis. Compounds 1-7, as well as four known related structures, were evaluated for cytotoxic activity against MDA-MB-435 (human melanoma cancer), MDA-MB-231 (human breast cancer), and OVCAR3 (human ovarian cancer) cell lines. Several of these natural products displayed significant cytotoxic activity, with humirianthenolide C being the most active.

Bioactivity-guided isolation of the antidiabetic principle in Pterocarpus Santalinoides leaf extract

Abstract Pterocarpus santalinoides is used in Nigerian ethnomedicine to treat diabetes mellitus. This study aimed to establish the antidiabetic property of the plant, and isolate and characterize its active principle. Dried and pulverized leaves (500 g) of P. santalinoides were extracted with 1.8 L of 80 % hydromethanol by cold maceration. The dried extract (10 g) was partitioned into n-hexane, ethyl acetate (EtOAc), n-butanol, and water. Antidiabetic activitiy-guided isolation by column chromatographic separation of the EtOAc soluble and purification of the sub-fractions by repeated preparative thin layer chromatography (pTLC) yielded a C-glycosyl flavonoid, identified as isovitexin. The chemical structure was elucidated based on high-resolution mass spectroscopy, 1D, and 2D nuclear magnetic resonance spectroscopic analyses. Alloxan-induced diabetic rat model was adopted for antidiabetic screening. The extract of P. santalinoides (100-200 mg/kg), fraction F4 (50 mg/kg), sub-fraction F4.3 (10 mg/kg), and the semi-purified compound F4.3.2 (5 mg/kg) significantly (p<0.05) reduced the fasting blood glucose of alloxan-induced diabetic rats, causing 48.4, 69.4, 57.7 and 64.5 % antidiabetic activity respectively, compared with > 68 % recorded in glibenclamide (2 mg/kg) control. These results reveal that isovitexin is the antidiabetic principle in P. santalinoides

Gongronema latifolium delays gastric emptying of semi-solid meals in diabetic dogs.

The aim of the study was to investigate sonographically the effect of Gongronema latifolium on gastric emptying of semi-solid meals in diabetic dogs. Twenty-five alloxan-induced diabetic dogs were randomly allotted into five groups of five dogs each in a randomised placebo-controlled study. These are placebo, prokinetic dose, low dose, moderate dose and high dose groups. The placebo group served as the control. The low, moderate and high dose groups ingested methanolic leaf extract of G. latifolium at 100 mg/kg, 250 mg/kg, 500 mg/kg respectively, while the prokinetic group ingested 0.5 mg/kg of metoclopramide. After a 12-hour fast, each group ingested its treatment capsules 30 minutes before the administration of test meal. Measurements of gastric emptying and blood glucose levels were obtained from each dog 30 minutes before and immediately after the ingestion of a test meal, every 15 minutes for another 4 hours and then every 30 minutes for further 2 hours. Gastric emptying of the moderate and high dose groups were 227.8 ± 9.9 min and 261.3 ± 19.3 min respectively and significantly (p < 0.0001) slower than the placebo control group of 143.0 ± 17.8 min. The gastric emptying of the low dose group (169.8 ± 3.8) and control group did not differ significantly (p > 0.05). A strong inverse relationship between gastric emptying and the incremental blood glucose levels was noted in the diabetic dogs after the ingestion of Gongronema latifolium (r = -0.90; p < 0.0001). Gonogronema latifolium delayed gastric emptying in diabetic dogs.

The antidiabetic activities of the methanolic root bark extract of Afzelia africana in alloxan-induced diabetic mice.

The methanolic root bark extract of Afzelia africana was tested for antidiabetic activities in-vivo. The acute toxicity of the extract was tested in mice and the result showed that the extract has low toxicity. Investigation on the phytochemical constituents of the plant extract revealed the presence of flavonoids, tannins, alkaloids, steroids and saponins. The plant extract was tested for antidiabetic activities in alloxan - induced diabetic mice at doses of 62.5 mg/kg, 125 mg/kg, 250 mg/kg, 500 mg/kg and 1000 mg/kg over a period of 6 hours. The activity was found to be both dose and time dependent. Optimum activity was noted at the dose of 250 mg/kg and 6 hours post treatment. Distilled water (10 ml/kg) and glibenclamide (2 mg/kg) were used as negative and positive controls respectively. The extract showed antidiabetic activity which did not differ significantly (p > 0.05) from glibenclamide. Column and thin layer chromatography revealed the presence of 5 fractions in the plant extract out of which fraction 3 was found to be active.

Glucose uptake-enhancing activity of the ethyl acetate extract of Dennettia tripetala in 3T3-L1 adipocytes.

Glucose uptake-enhancing activity of the ethyl acetate extract of Dennettia tripetala (EDT) was investigated using 3T3-L1 adipocytes. EDT yielded 4.43 percent w/w dry matter, showed the presence of alkaloids and flavonoids, contained calcium, iron, zinc, magnesium, copper and manganese. Out of the five extracts of D. tripetala, EDT gave the highest activity (75 percent) in enhancing glucose uptake in 3T3-L1 adipocytes, which was not significantly (p > 0.05) different from insulin (340 nM), the standard drug. EDT caused concentration-dependent increase in glucose uptake with maximal effect at 5 µg/ml, but further increase beyond 10 µg/ml caused a shut down in glucose uptake. Optimal effect was achieved at 16 h post incubation. There was no synergistic effect with increasing doses (2.5, 5.0, 10 µg/ml) of sub maximal concentrations of insulin, rather there was significant (p < 0.05) decrease compared with insulin (340 nM) alone. Unlike other protein inhibitors used, brefeldin significantly (p < 0.05) inhibited EDT-induced glucose uptake by more than 40 percent. In conclusion, EDT enhanced glucose uptake partly by the mobilization of glucose uptake proteins from the interior of the cell to plasma membrane via the Golgi apparatus. Therefore, this mechanism may be responsible for the antihyperglycaemic effect of EDT reported in our previous study.