Physicochemical standardization and antioxidant profiling of Astragalus hamosus L. pod oil (Roghan-e-Iklil-ul-Malik)

Abstract

Background: Fixed oils (Roghan) occupy an important position in Unani medicine as therapeutic agents and formulation vehicles. Astragalus hamosus L., whose pods are known as Iklil-ul-Malik in Unani medicine, is traditionally employed in inflammatory, neurological and tonic applications. Despite its long-standing use, systematic scientific data on the physicochemical quality attributes and antioxidant potential of its pod oil (Roghan-e-Iklil-ul-Malik) remain limited. The present study was undertaken to extract the fixed oil from authenticated pods of A. hamosus L., establish comprehensive physicochemical standardization parameters and evaluate its in vitro antioxidant activity using established analytical methods. Results: The fixed oil yield was 4.9% (w/w). The oil appeared greenish-yellow, clear and viscous with a characteristic odour. Moisture content was 2.5 ± 0.13% (w/w) and relative density at 25 °C was 0.90 ± 0.00. The oil was soluble in petroleum ether and diethyl ether and partially soluble in chloroform and ethanol. Kinematic and dynamic viscosities were 1.529 ± 0.018 St and 1.816 ± 0.005 Pa·s, respectively. The refractive index (nD25) was 1.5822 ± 0.00. Saponification, iodine, acid, ester and peroxide values were 187.2 ± 0.11 mg KOH/g oil, 68.5 ± 0.08 g iodine/100 g oil, 7.54 ± 0.02 mg KOH/g oil, 179.6 ± 0.11 mg KOH/g oil and 5.42 ± 0.06 meq O2/kg oil, respectively. The oil exhibited concentration-dependent DPPH radical scavenging activity with an IC50 value of 29.9 ± 0.023 µg/ml. Conclusion: The study establishes preliminary physicochemical quality benchmarks and standardization parameters for Roghan-e-Iklil-ul-Malik and demonstrates its appreciable antioxidant activity. These findings support the scientific validation, quality assurance and future pharmacological exploration of this traditionally important Unani oil. The generated data may serve as a reference framework for regulatory standardization and formulation development of Unani fixed oils. Furthermore, the results encourage advanced phytochemical characterization and in vivo studies to scientifically validate the proposed therapeutic properties and ensure safe, reproducible therapeutic use.