Chemical Profiling and In Vitro α-amylase Antidiabetic Assessment of Carissa Macrocarpa Flower Extract Cultivated in Saudi Arabia

Carissa macrocarpa is commonly known as Natal plum. Its fruits are palatable and used in manufacture of jams while other parts of the plant are used in traditional medicine to treat various diseases. The main objective of current study was to screen the presence of and isolate the various phytochemicals applying standard procedures and to evaluate the in vitro antidiabetic activity using α-amylase inhibitory assay. The total methanol extract of flower (TMEF) of Carissa macrocarpa was subjected to several chromatographic procedures. Results demonstrated that TMEF of Carissa macrocarpa is characterized by the content of different constituents such as flavonoids, steroids, saponins, tannins and carbohydrates at different levels. Chromatographic isolation led to the isolation of kaempferol-3-O-robinobioside and caffeic acid, which were confirmed via using ¹H, ¹³C, DEPT, COSY, HMQC and HMBC NMR spectroscopic analyses. TMEF exhibited α-amylase inhibitory activity with IC₅₀ value of 65.4 μg/ml when compared to that of the acarbose (standard) (IC₅₀ = 39.6 μg/ml). In conclusion, current investigation endorses the traditional use of Carissa macrocarpa as antidiabetic herb. Hence, the studied TMEF of Carissa macrocarpa may have the potential being nutraceuticals products for pharmaceutical applications as antidiabetic herbal remedy.