Preparation Inclusion Compound Of Fermentation Psidium Guajava L. Extract And In Vitro Digestion Simulation

As a natural tree tea,Psidium guajava L.leaves have been confirmed by a number of pharmacological experiments to help regulate blood sugar,antioxidant damage and other activities.It has a long history of drinking in Asia,Mexico,Peru and other places.Studies have confirmed that polyphenols and flavonoids in guava leaves play an important active role.However,there are only crude guava leaf tea products on the market,and the problems such as unstable quality of the functional ingredients,low utilization rate of active substances and poor mouthfeel,which seriously hinders the development of the natural resources.In this study,the content of polyphenols and flavonoids in guava leaves was improved by optimizing the fermentation condition.And the optimal extraction process of water/alcohol extracts was explored.Using β-cyclodextrin to encapsulated guava leaf extract,effectively improve the physicochemical properties of fermented guava leaf extract.Through the in vitro digestion simulation and antioxidant analysis,the bioavailability and stability of the fermented guava leaf extract inclusion complex(FGIC)were explored,which provided a theoretical basis for the promotion of guava leaf products.The specific results are as follows:In order to further improve the content of active substances in the fermented guava leaf extract,the fermentation times and water extraction/alcohol extraction process of guava leaves fermented by Monascus and Bacillus sp.was explored.The results showed that the total polyphenols and total flavonoids content of guava leaves reached the highest when the fermentation time was kept for 7 days,which were 45.37 mg GAE /g DM and 21.5 mg RE/g DM,respectively.The total polyphenol content increased by 2.24 and the total flavonoid content was increased by 1.61 times.The optimal process for water extracting is to control the temperature of 100 °C and time for 40 min,which can make the fermented guava leaf extract reach the highest content of polyphenols.The best ethanolic extraction process is to extract at a temperature of 55 ° C and an ultrasonic power of 240 W for 30 min.HPLC analysis showed that the content of rutin,isoquercitrin,quercetin,saponin,quercetin,quercetin-3-O-β-D-xylopyranoside,quercetin-3-O-α-L-arabinopyranoside and kaempferol in fermented guava leaves have been increased by fermentation.Among them,the growth of the core hypoglycemic substance quercetin reached 171.6%,and kaempferol increased by 162.5%.The growth rate also reached 111.2%.The fermented guava leaf extract was encapsulated by HP-β-cyclodextrin to obtain the inclusion complex(FGIC),and the preparation process of the inclusion complex was optimized.The entrapment rate of the FGIC reached 57.26% when the feed ratio was 1:5,the embedding temperature 50 ° C,the embedding time 2 h,and the stirring rate was 140 rpm.The obtained inclusion complex FGIC was characterized by ultraviolet spectroscopy(UV-vis),Fourier transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM)and thermogravimetric analysis(TGA),and the encapsulation offermented guava leaf ethanolic extract with HP-β-cyclodextrin was proved.The entrapment of the cyclodextrin limits the contact of the active substance functional groups of the extract with the free radicals,resulting in a slightly lower antioxidant capacity of the clathrate FGIC compared to the extract.The results showed that the DPPH free radical scavenging activity of guava leaf extract(IC50=105.2 ± 0.05 μg/ml)was slightly higher than that of FGIC(IC50=113.1±0.12 μg/ml).The ABTS+ radical scavenging test results showed slightly lower ABTS+ radical scavenging activity(IC50=70.26 ± 0.56 μg/ml)of FGIC compared to the extract(IC50=64.20 ± 0.14 μg/ml).The inhibition rate of α-glucosidase by fermented guava leaf extract(IC50=0.169±0.02 mg/ml)was also slightly higher than that of inclusion complex(IC50=0.197±0.01 mg/ml).Nevertheless,the experimental results of stability also confirmed that hydroxypropyl-β-cyclodextrin can protect the encapsulated fermented guava leaf extract and avoide the influence of the external environment on the active substance to enhance the stability of the active substance.Through in vitro digestion simulation,the changes of polyphenol flavonoids content and antioxidant capacity of fermented guava leaf extract and FGIC before and after digestion were explored,and the sustained release of cyclodextrin was confirmed.The results showed that the total polyphenols,total flavonoids and antioxidant capacity of extracts and inclusion complexes were significantly reduced after gastrointestinal digestion.Among them,the total polyphenols and total flavonoids contained in the inclusion compound are more released in the intestinal digestion.It was confirmed that cyclodextrin can protect the encapsulatedextract and reduce the effects of pH and enzymes.The change of the active substance in the digestion process is not completely consistent,and the degree of release of the inclusion compound in the stomach and intestinal medium depends on the influence of the pH environment on the compound and the embedding material.In this paper,the fermentation conditions of guava leaves was optimized,and the optimal process for extracting guava leaves was established,which provided a reference for the extraction of active ingredients from guava leaves.The preparation of FGIC provided a new idea for broadening the use of guava leaves and other traditional Chinese medicine resources.At the same time,the in vitro digestion model is estalished to simulate the digestion of the extract and inclusion complex in vivo.The sustained release of cyclodextrin on the extract laid the foundation for the development of fermented guava leaves into high value-added functional products.