In this study, alkaloid rich fraction from the stem powder Coscinium fenestratumwas studied for antidiabetic and anti-inflammatory activities as well as for other phytochemical contents. The antidiabetic activity of alkaloid rich fraction was evaluated with the use of three assays (inhibition of α-amylase, α-glucosidase and glucose uptake in yeast cell). Gas Chromatography and Mass Spectrophotometry analysis was used to determine the phytochemicals. Generally, the examined plants can be devised in two groups; the first one regrouped plants with high antioxidant activity (stem of Coscinium fenestratum). The antioxidant activity of extracts showed strong positive correlation with total phenolics and total flavonoids. The crude extracts had a lower level of sugars induced by the inhibitory effect of α-amylase, α-glucosidase and glucose uptake activities. Thus, their enzymatic inhibitory effect might have resulted from a synergism among the alkaloid compounds concerned.