Evaluation of Diuretic and Laxative Potential of Onosma bracteata Wall.: A Species of the Controversial Drug ‘Gojihva’

Background: Gojihva or Gaozaban, an Ayurvedic cum Unani Medicinal plant described with various properties, including diuretic activity. Onosma bracteata Wall. is considered the official species of Gojihva in Ayurveda and is one of the species considered Unani Gaozaban. Materials and Methods: The plant was subjected to physicochemical evaluation, sequential extraction, HPTLC profiling, and phytochemical screening. The diuretic and laxative activity of sequential methanol and water extracts of O. bracteata Wall. at a dose of 100 mg/kg and 200 mg/kg of body weight per oral was measured in Wistar rats in two separate experiments. Results: Preliminary phytochemical investigation and TLC profiling revealed the presence of flavonoids/hydroquinone/phenolics in methanol extract. Additionally, elemental analysis of plant material detected Potassium (K) at a level of 672.12 ppm. The methanol extract at doses 100 mg/kg (1.65 mL ± 0.19) and 200 mg/kg (2.00 mL ± 0.28) and aqueous extract at dose 200 mg/kg (1.63 ± 0.12) showed highly significant diuretic activity (p<0.0001) at 6 h compared to standard (0.67 mL ± 0.21). Whereas the aqueous extract of the plant showed mild constipation action. Conclusion: The literature search revealed that the diuretic potential of the methanolic extract could be attributed majorly to carbonic anhydrase inhibitory activity of constituent compounds like caffeic acid, rosmarinic acid, p-hydroxybenzoic acid, artitrichin, salvianolic acid, and coumarins, in addition to natriuretic, Ca2+ sparing activity, and increased renal excretory function. The milder diuretic action of the aqueous extract can be due to the presence of potassium salts in aqueous extracts. Thus, the traditional use of Gojihva as a diuretic is established on a phytochemical basis. Further pharmacological and phytochemical investigations of Methanol extract may reveal novel compounds with diuretic potential.