Scientific basis for medicinal use of Citrullus lanatus (Thunb.) in diarrhea and asthma: In vitro, in vivo and in silico studies.

Background: Citrullus lanatus (Thunb.) is a member of the Cucurbitaceae family, commonly farmed as an edible vegetable around the globe. It has been used in traditional therapies in addition to nutritional advantages. Traditional herbal practitioners employ C. lanatus seeds to treat gastrointestinal, respiratory, and urinary diseases in Pakistan and India. However, more investigation is needed to understand the effect of C. lanatus seeds on treating gastrointestinal, respiratory, and urinary disorders.

Purpose: This research aimed to use network pharmacology and molecular docking to understand multi-target mechanisms of C. lanatus seeds against asthma and diarrhea and to validate its effects using biological tests to investigate antispasmodic and bronchodilator capabilities.

Methods: The ground seeds of C. lanatus were extracted in hexane, dichloromethane, ethanol, and aqueous for sequential extracts. The bioactive components in sequential extracts of C. lanatus seeds were identified using LC ESI-MS/MS, and specific compounds were quantified using HPLC. The quantified bioactive compounds of C. lanatus were subjected to in silico studies for network pharmacology and molecular docking to elucidate their role in antispasmodic and bronchodilator properties. The sequential extracts were tested on isolated rabbit tissue, i.e., jejunum, trachea, and urinary bladder. The antiperistalsis, antidiarrheal and antisecretory studies were also performed in animal models.

Results: In silico studies indicate that bioactive chemicals from sequential extracts of C. lanatus seeds interfere with asthma and diarrhea-associated pathogenic genes. Those are members of calcium mediate signaling, cholinergic synapse, regulation of cytosolic calcium concentration, smooth muscle contraction, and inflammatory responses. It was also found that rutin, quercitrin, stearic acid, umbelliferone, and kaempferol were stronger binding to voltage-gated calcium channels and muscarinic M3 receptor, thus exerting calcium channel blocker activity and cholinergic receptor stimulant response. On isolated jejunum, trachea, and urinary preparations, sequential extracts of C. lanatus seeds elicited the spasmolytic response and showed the relaxation of spastic contractions of K (80 mM) and carbachol (1 µM). Furthermore, it induced a non-parallel rightward shift in calcium concentration-response curves with suppression. In animal models, C. lanatus seed extracts exhibited partially or completely antiperistalsis, antidiarrheal, and antisecretory effects.

Conclusion: Thus, Citrullus lanatus had therapeutic benefits by modulating the contractile response through calcium-mediated signaling target proteins, hence exerting bronchodilator and antidiarrheal properties. The current study provides evidence for further mechanistic studies and the development of C. lanatus seeds as a potential therapeutic intervention for patients with gastrointestinal, respiratory, and urinary disorders.