Research Article 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 Md. Nazmul Islam , Md. Fahim Hasan , Aishwarja Dey , Bishwajit Bokshi , Asish Kumar Das , Samir Kumar Sadhu , and Nripendra Nath Biswas Pharmacy Discipline, Life Science School, Khulna University, Khulna-9208, Bangladesh Correspondence should be addressed to Nripendra Nath Biswas; nnathbiswas@gmail.com Received 24 May 2022; Revised 23 June 2022; Accepted 16 August 2022; Published 19 September 2022 Academic Editor: Arham Shabbir Copyright © 2022 Md. Nazmul Islam et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Background. Avicennia officinalis is a medicinal plant that has traditionally been used as a diuretic, anti-infective, and anti- asthmatic. 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 AgNO 3 . 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 con- sistency; however, the chloroform fraction was found to be the most active (p < 0.001). e crude extract and n-hexane fractions significantly increased (p < 0.01) the urinary output at the dose of 200 and 400 mg/kg. e concentrations of Na + ,K + , and Cl - in collected urine were found to be more compared with the control group. e 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. 1. Introduction Historically, people have been using plants as a precursor of many important traditional as well as modern medicines since ancient times [1]. With the aims of getting novel and better therapeutic effects, reducing the side effects as well as total health care cost, people in this modern age still prefer traditional natural medicines over synthetic drugs in many cases. So far, a wide variety of plants’ secondary metabolites (e.g., flavonoids, phenols, glycosides, saponins, stilbenes, tannins, alkaloids, amines, betalains, terpenoids, etc.) have been reported to have many useful pharmacological prop- erties such as anticancer, antibacterial, analgesic, anti-in- flammatory, antitumor, and antiviral [2, 3]. e mangrove Hindawi Evidence-Based Complementary and Alternative Medicine Volume 2022, Article ID 4409250, 14 pages https://doi.org/10.1155/2022/4409250