Gas chromatography-mass spectrometry analysis and in vitro inhibitory effects of Phoenix dactylifera L. on key enzymes implicated in hypertension

Context: Phoenix dactylifera (PD) is a medicinal plant reportedly used in folklore for hypertension management. Scientific validation for its use as an antihypertensive agent is scanty. Aims: To investigate the bioactive compounds present in extract and differential solvent fractions, and the in vitro inhibitory effect of PD on the activities of key enzymes associated with hypertension. Methods: Ethanol and differential solvent (ethyl acetate, butanol and water) fractions of PD were prepared using established methods and were thereafter used for the enzyme inhibition assays, which includes: angiotensin-converting enzyme (ACE), acetylcholinesterase (AChE), phosphodiesterase-5 (PDE-5), adenosine deaminase (ADA) and arginase. Gas chromatography-mass spectrometry was used to evaluate bioactive compounds present in the extracts and fractions. Results: Preliminary phytochemical evaluations revealed the presence of tannins, flavonoids, betacyanins and phenols in all solvent fractions. Some of the compounds detected in P. dactylifera that have been implicated in hypertension management include squalene, lauric acid, palmitic acid, caprate, stearate, vitamin E, β-sitosterol, phytol, linolenic acid, isosorbide, coumarins and taurine. Furthermore, all except the aqueous fraction exerted significantly (p<0.05) higher ACE inhibition than the control drug (lisinopril). Also, the ethanol, butanol, and aqueous fractions exerted significantly (p<0.05) higher inhibition of PDE-5 than the control drug (sildenafil). However, the aqueous fraction exhibited the highest PDE-5 and AChE inhibition at 86.99 ± 0.10 and 91.81 ± 1.20%, respectively. Also, the aqueous fraction had the highest inhibitory effect on ADA (82.87 ± 4.32%). Conclusions: These findings, therefore, justify the use of P. dactylifera as an antihypertensive agent in the folklore medicine.