Antidiabetic Screening of Phenolic-rich Extracts of Selected Medicinal Spices

Medicinal spices are used by herbal practitioners as condiments in decoctions for management of diabetes and its associated complications. The study assessed and compared the potentials of phenolic-rich extracts from four selected medicinal spices: Curcuma longa; Allium sativum; Xylopia aethiopica and Syzygium aromaticum to delay carbohydrate digestion, scavenge free radicals and ameliorate hyperglycemia. Results showed that the seed of X. aethiopica has the highest phenolic content (19.25 ± 0.96 mg/g) while C. longa extracts was the lowest (10.42 ± 0.86 mg/g). Dose-dependent in vitro bioactivities were exhibited by all the spice extracts, with the best antiradical (EC50 = 64.98 ± 5.16 µg/ml) and α-amylase inhibitory (IC50 = 11.33 ± 1.10 µg/ml) activities displayed by A. sativum and S. aromaticum, respectively. Intraperitoneal administration of either of the spice extracts for 5 days caused significant reduction (> 80%) in hyperglycemia. The antidiabetic activities of the spice extracts may be attributed to the presence of notable secondary metabolites such as tumerone and its derivatives in C. longa extract or eugenol that was the main constituent of the extract from S. aromaticum and also found in minor quantities in A. sativum and X. aethiopica extracts. These findings showed that extract from these spices could be explored as a functional component of foods or as candidates for development of oral antihyperglycemic agents for the management of diabetes mellitus.