Optimization of alkaline extraction process and biological activity of polysaccharides from foxtail wood leaves using response surface methodology
Premna puberula Pamp, also known as Long stemmed Stinky Yellow Chestnut and Immortal Tofu Chai, belongs to the family Verbenaceae and the genus Tofu Chai. It is a medicinal and edible plant; Foxtail wood leaves contain abundant active substances such as flavonoids, polyphenols, volatile oils, and polysaccharides, which have antioxidant, antibacterial, anti-tumor, and anti-inflammatory effects. At present, research on the leaves of Eucommia ulmoides mainly focuses on the extraction of active ingredients, pharmacological effects, and applications in food processing. Polysaccharides are the main functional components in the leaves, and the pectin content is as high as 35.53%. The research on polysaccharides in the leaves of stinky wood mainly focuses on the extraction, antioxidant, and anti-inflammatory properties of acid soluble and water-soluble polysaccharides. Shi et al. compared the effects of acid extraction, alkali extraction, and ammonium oxalate ultrasound assisted extraction on the antioxidant activity of tofu wood pectin. The results showed that the alkali extraction method had the best DPPH free radical and hydroxyl free radical scavenging ability, and its antioxidant activity was superior to the other two extraction methods. The main research on alkali soluble polysaccharides in the leaves of Foxtail wood is focused on polysaccharide extraction, and the extraction process has not been systematically studied. However, there have been no reports on the anti-tumor activity of alkali soluble polysaccharides in China.
This article aims to fully develop and utilize the polysaccharide resources of Eucommia ulmoides, using the residue of polysaccharides extracted by the folic acid method of Eucommia ulmoides as raw material. Single factor and response surface experiments were conducted to optimize the extraction process of alkaline soluble polysaccharides (PLAP) from Premna puberula Pamp leaves, and to explore the in vitro antioxidant capacity and anti-tumor activity of PLAP. The aim is to provide theoretical support for maximizing the utilization of Eucommia ulmoides resources and its application in functional food research and pharmaceutical fields.

This experiment used the residue extracted from the leaves of Eucommia ulmoides by acid extraction method as the raw material, and NaOH solution as the extraction solution. The optimal extraction process for PLAP was obtained through single factor and response surface experiments: liquid to material ratio of 1:50g/mL, NaOH concentration of 0.25mmol/L, extraction time of 110min, and PLAP extraction rate of (11.80 ± 0.50)% under these conditions; PLAP has good antioxidant capacity, with IC50 values of 0.18, 3.22, and 12.38 mg/mL for ABTS radicals, hydroxyl radicals, and DPPH radicals, respectively; The anti-tumor activity experiment showed that PLAP has a certain inhibitory effect on the proliferation of A549 and HepG2 cells, both showing a significant dose effect (P<0.05). PLAP has a better inhibitory effect on the migration of A549 and HepG2 cells, and there is a significant difference compared with the blank group; This study maximizes the utilization of polysaccharides from the leaves of Eucommia ulmoides, and the PLAP extracted sequentially from Eucommia ulmoides has high biological activity, which can provide theoretical support for research in food processing and medicine.