Abstract:In this work, the release of essential oil from guava leaves during the solid-state fermentation of guava leaf substrate with mixed strains, Monascus anka and Bacillus megaterium, were investigated. The results showed that the 20 main components in the guava leaf essential oil remained unchanged after fermentation, but the rate of essential oil extraction increased significantly and reached 6.53 times that of the unfermented group after 10 days of fermentation. Tissue structure analysis combined with enzymatic analysis inferred that glycosidases destroyed the cell walls, glandular trichomes, and vacuoles of guava leaves, and cleaved the intersugar linkages and glycosidic bonds, to promote the release of aromatic compounds from guava leaves. After fermentation, the DPPH radical scavenging ability of 2,2-diphenyl-1-picrylhydrazyl in guava leaf essential oil decreased by 26.15%, but the ABTS+ radical scavenging ability and 5-lipoxygenase inhibitory capacity and tyrosinase inhibitory capacity of 2,2'-azino-bis(3-ethylbenzothiazoline-6- sulfonic acid) diammonium salt increased by 32.66%, 18.73% and 7.87%, respectively (with the corresponding IC50 values reaching 20.47±2.49 mg/mL, 23.21±1.92 μg/mL and 107.41±3.48 μg/mL, respectively). Overall, fermentation can improve the antioxidant and biological activities of the guava leaf essential oil. The results may provide a new insight into the efficient extraction of fruit leaf essential oils and a pathway for the development of novel natural health products.
