Optimization and evaluation of rhein-rich Senna alata leaf extract incorporated shellac electrospun nanofibers using design of experiments

Abstract

Rhein, a key component of anthraquinones, is a crucial active compound in Senna alata leaves with a variety of pharmacological effects. Achieving high-quality herbal extracts necessitates selecting suitable extraction methods for each plant. In this study, a systematic approach involving single-factor analysis and Box-Behnken design was used to optimize ultrasound-assisted extraction (UAE) conditions for rhein-rich extracts. The rhein content was quantitatively determined using a validated high-performance liquid chromatography–diode array detection (HPLC–DAD) method. The optimal extraction conditions were identified as 95% v/v aqueous ethanol used as solvent, 59.52 ºC, and 18.4 min, with a solvent-to-solid ratio of 25.48:1 mL/g, yielding a predicted rhein content of 10.44 mg/g extract. The research aimed to incorporate these extracts into shellac electrospun fibers. Through fractional factorial design and Box–Behnken design, optimal electrospinning conditions was established as a voltage of 24 kV, a solution feed rate of 0.8 mL/h, and a shellac–extract ratio of 38.5:3.8 (% w/w) resulting in nanofibers with a diameter of 306 nm, low bead-to-fiber ratio (0.29), and 96% extract entrapment efficiency within nanofibers. The results revealed that the concentration of shellac significantly influenced both the diameter of the fibers and the formation of beads. In vitro release studies revealed a biphasic profile with an initial rapid release of 88% within the first hour, followed by a sustained release pattern exceeding 90% over the subsequent 12 hours, as anticipated based on zero-order release kinetics.The fiber mats incorporated with the extract remained stable for 60 days when subjected to 40°C temperature and 75% relative humidity during stability testing. The optimized extract and nanofibers displayed antimicrobial efficacy against various pathogens. These findings indicate that rhein-rich extracts and their incorporation into shellac electrospun fibers exhibit significant biological activities for potential therapeutic and cosmetic applications.

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