Inhibitory Actions of Ethanolic Fraction of Sida linifolia L. Leaves on Erectile Dysfunction-Relevant Enzymes in Male Rat Penile Tissue Homogenates: An ex-vivo and in-silico Approach

Erectile dysfunction (ED) is a prevalent male sexual disorder frequently associated with impaired nitric oxide signaling, heightened oxidative stress, and the dysregulation of key enzymes such as acetylcholinesterase, arginase, phosphodiesterase-5 (PDE-5), and angiotensin-I converting enzyme (ACE). Limitations of current pharmacotherapies, including side effects and incomplete efficacy, have spurred interest in plant-derived bioactive compounds as alternative or complementary treatments. Although Sida linifolia is traditionally used for managing reproductive and inflammatory conditions, its mechanism of action remains unclear. This study explored the propensity of the ethanolic fraction of S. linifolia leaves (EtOHFSL) to inhibit enzymes linked to erectile dysfunction in rat penile tissue homogenate. Enzyme inhibition assays were conducted using rat penile tissue homogenates, while phytochemical constituents were identified using gas chromatography coupled with flame ionization detection (GC-FID) and supported by high-performance liquid chromatography (HPLC) profiling to confirm compound composition. Molecular docking studies (MDS) were performed using AutoDock Vina. Identified compounds in EtOHFSL included epicatechin, flavone, rutin, kaempferol, lunamarin, naringenin, ellagic acid, quercetin, and chlorogenic acid. EtOHFSL demonstrated moderate, concentration-dependent inhibition of PDE5, arginase, ACE, and AChE, with IC₅₀ values ranging from 0.66–0.84 mg/mL, which were compared cautiously with the respective pure reference inhibitors (sildenafil, L-NOHA, captopril, and galantamine) for reference purposes only. Molecular docking of experimentally confirmed phytochemicals such as epicatechin, rutin, kaempferol, lunamarin, and ellagic acid revealed strong binding affinities to ED-related enzymes. The in-vitro results corroborated in-silico molecular docking predictions, suggesting consistent inhibitory trends. In-silico ADMET predictions further indicated acceptable pharmacokinetic and toxicity profiles for most compounds. These preliminary findings suggest that S. linifolia contains bioactive constituents with enzyme modulatory potential against ED-related targets; however, further purification, isolation of active principles, and in-vivo validation are required to substantiate any therapeutic claims.