Preparation And Protective Effect Of Pectin From Premna Microphylla Turcz On UVB-Induced Skin Damage

Premna microphylla Turcz,which is a plant with high edible and medicinal value,is widely distributed in our country.Premna microphylla Turcz can bring high economic benefits with a long harvest period and strong regeneration ability.Leaves of Premna microphylla Turcz are an ideal source of commercial pectin with rich pectin,which can increase added value of Premna microphylla Turcz and has great development and utilization value.Ultrasonic disruption technology can effectively increase the yield of target substance and shorten the extraction time with cavitation effect,which is a green and economic method for extracting pectin from Premna microphylla Turcz.In recent years,skin diseases induced by ultraviolet have aroused people’s attention to skin health.According to the wavelength difference,UV can be classified as UVA,UVB,and UVC.Among them,UVB,which has high energy and strong genotoxicity,is the main source of skin damage.As a soluble polysaccharide,pectin has good antioxidant properties and moisturizing effects,which means it has the potential protective effect on UVB-induced skin damage.Therefore,pectin was extracted from Premna microphylla Turcz with ultrasonic disruption technology,and extraction condition parameters were optimized.Different properties of four pectins obtained by ultrasonic disruption and the other three methods were compared.In addition,protective effect of pectin from Premna microphylla Turcz on UVB-induced skin damage and possible mechanisms were explored through animal experimental model.The aim of this study is to provide theoretical support for development of Premna microphylla Turcz resources and application of pectin from Premna microphylla Turcz.The main conclusions are as follows:（1）Parameters of ultrasonic disruption technology to extract pectin from Premna microphylla Turcz were optimized through single-factor and response surface method.The results showed that the order of the influence of each factor on the response value is:liquid-to-material ratio>ultrasound power>ultrasound time.After comprehensively considering extraction efficiency and cost of pectin from Premna microphylla Turcz,it was determined that the liquid-to-material ratio was 60 m L/g,the ultrasonic power was525 W,the ultrasonic time was 8 min,and the final yield was 25.58±0.81%.（2）Physicochemical properties,structural and functional characteristics of pectins from Premna microphylla Turcz obtained by ultrasound,enzyme,ultrasound-enzyme and enzyme-ultrasound respectively were measured.Pectin extracted by ultrasonic disruption technology（U-P）was quite different from the pectin extracted by the other three methods.The results showed that extraction rate of the pectins obtained by four extraction methods were 19～40%,the appearance were light yellow,and the purity reached more than 60%,the purity of U-P was the highest,reaching 84.38%.Degree of esterification of the pectins were less than 50%,which means they were low-ester pectin.DE of U-P was 45.94%,which was significantly higher than the other three pectins.Rhamnose,D-galacturonic acid,galactose and fucose were their main monosaccharides.RG-I type were their main structure.Structure of U-P had the shortest side chains,the highest linearity,and the smallest molecular weight.Absorption peak of pectins was detected at 200～300 nm,infrared spectrum showed that the four pectins have characteristic peaks of carbohydrates.X-ray diffraction analysis results showed that U-P had the highest crystallinity.The thermal stability results showed that pectins obviously changed at around 50～100℃and200～300℃,which maybe caused by water evaporation,monosaccharide decarboxylation or glycosidic bond breakage.Moreover,the peak of U-P appeared in thermal stability tests were more to the right,enthalpy value and weight change were lower,which means it had better stability at high temperatures.Rheological results showed that pectins from Premna microphylla Turcz had obvious shear thinning phenomenon,which means they were a non-Newtonian fluid,and viscosity of the pectins were concentration-dependent.Fluid of pectins were gel-like with good elasticity.Besides,U-P had the lowest apparent viscosity,G′and G″,which means its fluid properties is more obvious.Anti-oxidation results showed that DPPH·,ABTS⁺·clearance rate and iron reducing power of the four pectins increased with the increase of the concentration.IC₅₀ value of DPPH·and ABTS⁺·of U-P were the lowest,and the iron reducing power effect was the highest,which showed that U-P had the best oxidation resistance.（3）Protective effect of pectin from Premna microphylla Turcz on skin damage of Balb/c mice induced by UVB was explored,and results showed that the application of high-dose pectin cream（H-P）can relieve symptoms like skin redness,peeling,and ulceration caused by UVB,and effectively inhibit thickenging of epidermis and disordered arrangement of collagen fibers caused by UVB.H-P can reduce adverse effects of UVB on the growth of mice.H-P promoted the increase of antioxidant enzymes content in mice and improved antioxidant capacity of mice to reduce oxidative damage caused by UVB.H-P inhibited the increase of matrix metalloproteinases-1 and boosted the increase of typeⅠ,III collagen in mice,which has a good effect on maintaining normal content of collagen in mice skin.H-P has an inhibitory effect on the increase of pro-inflammatory factors induced by UVB,promoted the expression of anti-inflammatory factors,and inhibited UVB-induced skin inflammation.The above phenomena proved that H-P has a positive significance in avoiding a series of adverse skin symptoms such as epidermal thickening,oxidative stress,collagen loss and inflammation caused by UVB,which can prevent UVB-induced skin damage.（4）The possible mechanism of the protective effect of pectin from Premna microphylla Turcz on UVB-induced skin damage was explored,and the results showed that the pectin from Premna microphylla Turcz can promote the expression of Nrf2 and HO-1 protein and the activation of Nrf2 signaling pathway,and this phenomenon is dose-dependent.The concentration of pectin from Premna microphylla Turcz in the cream is negatively correlated with the content of IKKβ,NF-κB,COX-2 protein in mice skin.Pectin from Premna microphylla Turcz can inhibit the increase of UVB-induced activation of NF-κB signaling pathway.It is speculated that pectin from Premna microphylla Turcz may protect mice skin from oxidative damage,inflammation and collagen degradation caused by UVB through NF-κB and Nrf2 signaling pathway.