Identification of Potential Diuretic and Laxative Drug Candidates from Avicennia officinalis L. Bark through In Vivo Mice Model Studies and In Vitro Gas Chromatography-Mass Spectrometry and Molecular Docking Analysis

Abstract

Background. Avicennia officinalis is a medicinal plant that has traditionally been used as a diuretic, anti-infective, and antiasthmatic. Our investigation was designed to explore the diuretic and laxative potentials of different fractions of this plant’s bark extract as well as the identification of possible drug candidates for the activity. Methods. Collected bark was extracted in ethanol and fractionated in different polar and nonpolar solvents, i.e., water, chloroform, ethyl acetate, and n-hexane. Phytoconstituents were identified following the published protocols and gas chromatography-mass spectrometry (GC-MS). In the diuretic test, Na+ and K+ ions were measured using a flame photometer whereas the Cl− ion content was measured by titrimetric method against AgNO3. In the laxative test, feces amount and consistency were also measured. Molecular docking analysis was conducted using the “Vina Wizard” program in PyRx-Python Prescription 0.8. Results. Phytochemical analysis indicated that alkaloids, tannins, flavonoids, saponins, glycosides, and terpenoids were detected in the most bioactive crude extracts, whereas alkaloids, terpenoids, saponins, and gums were found in bioactive n-hexane fraction and steroids, glycosides, and terpenoids were found positive in chloroform fraction. Almost all the fractions demonstrated a dose-dependent increment of stool production with a soft consistency; however, the chloroform fraction was found to be the most active ( $p$  < 0.001). The crude extract and n-hexane fractions significantly increased ( $p$  < 0.01) the urinary output at the dose of 200 and 400 mg/kg. The concentrations of Na+, K+, and Cl− in collected urine were found to be more compared with the control group. The GC-MS analysis identified seven compounds in bioactive n-hexane fraction (phenolic and ester-type mainly) whereas seven other compounds (acidic and ester-type mainly) were identified in chloroform fraction. In molecular docking, two drug candidates of this extract (2,4-bis(2-phenylpropan-2-yl)phenol and 2-[4-[2-(dimethylamino)-2-oxo-1,1-diphenylethyl]phenyl]-2-phenylacetic acid) showed excellent binding affinity with the receptor compared with furosemide. Conclusion. A. officinalis bark might be a potential source of bioactive compounds for treating hypertension, edema, and constipation.