Antidiabetic activity-guided isolation of gallic and protocatechuic acids from Hibiscus sabdariffa calyxes

We isolated and identified gallic and protocatechuic acids as the antidiabetic principles in Hibiscus sabdariffa using solvent extraction, column chromatographic fractionation, and nuclear magnetic resonance (NMR) spectroscopy. Ethylacetate fraction of the aqueous extract of H. sabdariffa inhibited alpha-amylase and alpha-glucosidase with IC50 of 411.73 and 433.93 mu g/ml, respectively. Furthermore, fractions I and II obtained from column chromatography inhibited alpha-amylase with IC50 of 27.03 and 20.12 mu g/ml, and alpha-glucosidase with IC50 of 24.30 and 22.29 mu g/ml, respectively. In addition, the principles reduced the serum glucose and lipid peroxide levels of diabetic rats and with an improvement in the rat lipid profiles and antioxidant defenses. Fractions I and II were identified as protocatechuic acid and gallic acid, respectively, using H-1 and C-13 NMR. Protein-ligand docking showed that these compounds form multiple favorable interactions with the active-site residues of the two glycosidases. Overall, protocatechuic and gallic acids emerge as natural antidiabetic agents. Practical applications Hibiscus sabdariffa (Zoborodo) is a refreshment drink for ceremonial gatherings in Nigeria. Also, its pharmacological use includes diabetes, hypertension, hyperlipidemia, metabolic syndrome, and hepatoprotection. The consumption of this food drink could improve diabetes, hypertension, dyslipidemia, metabolic syndrome, and liver disease. Furthermore, the inhibition of alpha-amylase and alpha-glucosidase could prevent diabetic complications associated with postprandial glucose. Developing the extract of H. sabdariffa calyx as food supplement could be used in managing diabetes and its associated complications such as dyslipidemia, hypertension, and metabolic syndrome.