Statistical optimization of microwave-assisted extraction of phytochemicals from Retama raetam (White Weeping Broom) twigs and their biological properties

Abstract

Background: Several phytochemicals from the genus Retama genus are claimed to have multiple biological activities, including antioxidant, anti-inflammatory, and antibacterial activities.

Aims: The aim of this study was to optimize microwave-assisted extraction (MAE) of polyphenols from Retama raetam twigs using response surface methodology.

Material and Methods: The Box-Behnken design was utilized for determining the effect of MAE factors on total polyphenol content (TPC), including ethanol concentration (50–70%), irradiation time (4–6 min), power (400–600 W), and solvent-to-sample ratio (15–25 mL/g). Additional assessment was performed for the optimal extract (OE) to assess its total flavonoid content (TFC), condensed tannin content (TTC), and antioxidant activity (DPPH• scavenging and FRAP). The in vitro anti-inflammatory activity assessment of the OE was evaluated using two complementary assays (albumin denaturation and membrane stabilization).

Results: The following conditions: ethanol concentration of 64.73%, irradiation time of 5.57 min, power of 569.16 W, and solvent-to-sample ratio of 22.91 mL/g, resulted in the highest TPC (181.48 ±1.59 mg GAE/g DR). The effectiveness and statistical validity of the derived quadratic model indicated no significant discrepancy between the experimental and predicted results, demonstrating its high accuracy. In addition, the obtained OE presented a TFC of 31.25 ±1.5 mg EC/g DR and a TTC of 15.17 ±1.56 mg EC/g DR. The OE showed a significant capacity to scavenge DPPH• and an appreciable ferric-reducing power, where the IC₅₀ and EC₅₀ values were respectively 0.44 ±0.08 and 0.61 ±0.03 mg/mL. The OE at a concentration of 1.5 mg/mL showed moderate anti-inflammatory activity by red blood cell membrane stabilization (72.72 ±0.73%) and reducing heat-induced albumin denaturation (50.89 ±0.66%).

Conclusion: The MAE of TPC was mainly influenced by EtOH concentration, irradiation time, and power. The OE exhibited moderate antioxidant and anti-inflammatory properties, suggesting that it may be a good source of phytopharmaceuticals.

Keywords: Retama raetam, microwave-assisted extraction, optimization, antioxidant, anti-inflammatory.