Optimization for ultrasound combined with flash extraction of polysaccharides from Phyllanthus emblica L. with...

Ultrasound-assisted flash extraction was used to rapidly extract polysaccharides from Phyllanthus emblica L. fruits (PEPs) with a good yield of 9.73 % ± 0.75 %. Furthermore, the PEPs were fractionated by graded precipitation of 30 %, 60 %, and 90 % (v/v) ethanol solution, and the respective molecular weight polysaccharide fractions, namely PEP-30 (166.88 kDa), PEP-60 (109.14 kDa), and PEP-90 (34.59 kDa) were obtained. The three fractions were composed of similar monosaccharides with galacturonic acid as the main constituent. The slope of R.M.S. radius-Mw curve showed that the three polysaccharide fractions were high-branched molecules with solid spherical conformation, and PEP-90 adopted a more compact conformation in aqueous solution. The three polysaccharide fractions had strong antioxidant activity, with PEP-60 showing the strongest antioxidant effect in vitro. PEP-30 (IC₅₀ = 1.56 ± 0.14 mg/mL), PEP-60 (IC₅₀ = 0.99 ± 0.09 mg/mL), and PEP-90 (IC₅₀ = 0.63 ± 0.09 mg/mL) all exhibited mixed-type inhibition of α-glucosidase. Notably, PEP-90 showed the strongest inhibitory effect on α-glucosidase with the strongest binding ability to α-glucosidase and α-glucosidase-substrate complex, which are mainly related to different molecular weight. The results suggest the molecular weight of PEPs had great impact on their biological activities, providing important theoretical guiding for developing Phyllanthus emblica L. food products with the functional activity.