Vacuum dried mulberry leaf powder: A promising functional ingredient and its application in alginate beads

Background and objectives: Mulberry (Morus alba L.) leaf has been consumed as tea and seasoning powder in many Asian countries. Additionally, it is a well-known folk medicinal plant which have various pharmacological activities. Mulberry 1-deoxynojirimycin (DNJ) is a biologically active natural compound that exhibits hypoglycemic effect. This study aims to compare the active compounds and biological activities of leaf powder after vacuum (VML) and sun (SML) drying process, and in food application. Methods: DNJ and total phenolics (TP), in vitro α-glucosidase inhibitory, and antioxidant (FRAP and ORAC assay) activities of VML and SML were evalutated. The selected powder with high amount of the active compounds and the biological activities was further evaluated the potential applications in food by addition in alginate beads, and reduced the harmful microorganism using high pressure processing (HPP) at 100 and 300 MPa for 5 min. The final products were compared those parameters with non-treatment sample. Results: Our results showed the vacuum drying process had overcome sun dry method. The content of active compounds and the in vitro health benefits of VML were greater than that of SML (DNJ 614.05 ± 40.82 921.88 ± 33.14 µg/g; TP 14.93 ± 0.82 and 11.95 ± 0.10 mg gallic acid equivalent (GAE)/g; percent inhibition of α-glucosidase 77.34 ± 1.00 and 66.36 ± 1.07; FRAP value 60.86 ± 1.32 and 56.48 ± 0.96 µmol trolox equivalent (TE)/g; ORAC value 748.32 ± 35.11 and 604.80 ± 31.45 µmol TE/g in VMB and SMB, respectively). The VML was selected, and added in the alginate bead system. The HPP either 100 or 300 MPa did not reduce active components and in vitro health benefits (DNJ 8.31-8.79 µg/g; TP 9.21-9.64 mgGAE/g; percent inhibition of α-glucosidase 62.49-65.93; FRAP25.75-28.70 µmol TE/g; ORAC 158.76-162.63 µmol TE/g). Conclusion:s: In summary, vacuum dried mulberry leaf powder is a potent functional ingredient that can be applied in food for reduce blood glucose. Our result showed that the HPP prevents loss of the both active compounds and their function. For further study, the clinical trial of the products should be conducted in order to support the health benefit of final products.