Optimization of Ultrasound-Assisted Deep Eutectic Solvent Extraction, Characterization, and Antioxidant, Hypoglycemic, and Immunoregulatory Activities of Polysaccharide from the Ficus pumila Linn.

This study focuses on the resource utilization of Ficus pumila Linn. (FPL) by valorizing its often-discarded hulls, aiming to reduce waste and enhance material value. An ultrasonic-assisted deep eutectic solvent (DES) extraction method was optimized using response surface methodology to obtain polysaccharides (FPLP). The optimal DES system was choline chloride:oxalic acid at a molar ratio of 1.5:1, DES water content of 54%, ultrasonication time of 55 min, extraction temperature of 69°C, liquid-to-solid ratio of 21:1 mL/g, and ultrasonic power of 240 W. Under these conditions, the extraction yield of FPLP reached 0.9524%. This yield was 4.44- and 1.45-fold higher than those achieved by conventional hot-water and ultrasonic-water extraction, respectively. The crude FPLP was further purified by DEAE and Sephadex G-75 chromatography to obtain a refined polysaccharide, FPLP-1. Bioactivity evaluations demonstrated that FPLP-1 exhibits in vitro antioxidant activity (ABTS·+ scavenging IC50 = 2.587 mg/mL) and hypoglycemic potential (α-amylase inhibition IC50 = 1.560 mg/mL). Moreover, FPLP-1 showed potent in vivo antioxidant effects by protecting zebrafish keratinocytes from metronidazole-induced apoptosis, along with broad in vitro immunomodulatory functions, including promoting splenocyte proliferation, enhancing macrophage phagocytosis, and stimulating the secretion of NO, TNF-α, and IL-6 in a concentration-dependent manner. These findings highlight the promising potential of FPLP-1 as a multifunctional bioactive compound.