Advances in Endophytic Fungi Diversity and Secondary Metabolites in Rhizophora Plants

Mangroves are composed of a large group of salt-tolerant plant communities growing in tropical and subtropical intertidal estuarine zones, which are distributed approximately in the area between 30° N and 30° S latitude. Rhizophora genus is a kind of mangroves,and all woody plants located in tropical and subtropical intertidal coastal regions, and comprises of 8 species, including R. stylosa, R. apiculata, R. mucronata, R. mangle, R. harrisonii, R. racemosa, R. annamalayana and R. samoensis. Those plants have the characteristics of salt stress, high mineral composition, strong reducibility and frequent tides, which make plants extremely competitive for nutrition and space. The special growth environment entriches the diversity of endophytic fungi in Rhizophora, and it is bound to produce active molecules with biological activity and unique chemical structure different from other ecosystems. So far, the endophytic fungi isolated from Rhizophora genera are reported with 23 orders, 41 families and 64 genera. Amongst, Pestalotiopsis, Penicillium and Mucor have been widely studied. Meanwhile, 195 secondary metabolites have been identified from the Rhizophora endophytic fungi, including alkaloids, terpenoids, coumarins, ketones, quinones, anthraquinones, peptides, phenolic acids, lactones and other compounds. Some secondary metabolites with unusual structures are identified in Rhizophora endophytic fungi. Novel hybrid sesquiterpene-cyclopaldic acid metabolites with unusual carbon skeletons, pestalotiopens A and B (83, 84), pestalotiopsones A-F (107-112)are obtained from the endophytic fungus Pestalotiopsis sp. JCM2A4 is isolated from the leaves of the Chinese mangrove, R. mucronata. Most of them show antitumor, antibacterial, antioxidant activities. Some compounds have significant bioactivities, as exemplified by pestalpolyol 1 (119), a novel polyketone derivative isolated from P. clavispora. Compound 119 has a strong inhibitory effect on mouse lymphoma cell line L5178Y with an IC50 value of 4.10 μmol•L-1. The indole diterpene alkaloids, rhizovrin A, B and F (46, 47, 50), isolated from endophytic fungi Mucor irregularis QEN-189, have strong inhibitory effects on lung cancer cells A549, with IC50 values of 11.5, 6.3 and 9.2 μmol•L-1, respectively, as well as inhibitory effects on leukemia myeloid cells HL-60, with IC50 values of 9.6, 5.0 and 7.0 μmol•L-1, respectively. © 2019, Editorial Department of Scientia Silvae Sinicae. All right reserved.