Bioactive secondary metabolites from two sponge-derived actinomycetes

Actinomycetes residing in marine habitat are an excellent treasure house of structurally novel and Received: 2022-01-10; Accepted: 2022-06-06; Online (CNKI): 2022-08-09 Foundation: Hainan Provincial Basic and Applied Basic Research Fund for High-Level Talents in Natural Science (2019RC306, 2019RC352); Central Public-Interest Scientific Institution Basal Research Fund for CATAS-ITBB (1630052022028, 1630052022016, 1630052019011); Financial Fund of the Ministry of Agriculture and Rural Affairs of China (NFZX2021) Corresponding author: Associate professor GUO Zhikai. E-mail: guozhikai@itbb.org.cn Associate professor LI Ming. E-mail: liming0898@163.com Citation: GUO Zhikai, WANG Rong, WU Weicheng, et al. Bioactive secondary metabolites from two sponge-derived actinomycetes [J]. Journal of Shenzhen University Science and Engineering, 2022, 39(5): 550-558. (in Chinese) 第 5期 郭志凯,等:两株海绵放线菌产生的抗菌活性产物研究 http://journal.szu.edu.cn bioactive natural products with potent medicinal values. To exploit chemically diverse and bioactive natural products from actinomycetes living in underexplored ecological niche, we isolate a large number of marine actinomycetes from marine sponges, corals, algae, mollusks, sea grasses, and sediments collected from the South China Sea. In order to assess the values of these special marine actinomycetes in the green development of tropical agriculture, we screen the activity of marine actinomycetes against phytopathogenic fungi and bacteria. As a result, we identify two strains of sponge-derived actinobacteria Streptomyces sp. HMH1 and HML1 possessing antagonism effect against tested phytopathogenic microbes. The secondary metabolites produced by these two actinomycete strains and their antiphytopathogenic fungi activity are investigated. The secondary metabolites from the fermentation extract of Streptomyces sp. HMH1 and HML1 are isolated and purified using various chromatography methods including silica gel column, reverse gel column and Sephadex LH-20 column chromatography. The structures of the isolated compounds are characterized by NMR, HR-ESI-MS spectroscopic data analyses and comparison with previously reported data. Three major compounds belonging to the family of actinomycin are purified from the solid fermentation extract of the sponge-derived actinobacterium Streptomyces sp. HMH1. They actinomycin D, actinomycin X2, and actinomycin Xoβ. A compound identified as K-252d belonging to the family of indolocarbazole alkaloid is isolated from the solid fermentation extract of another sponge-derived actinobacterium Streptomyces sp. HML1. The antiphytopathogenic fungi and bacteria activities of these compounds are evaluated against ten species of plant pathogenic fungi including Fusarium oxysporum FOC4, Lasiodiplodia theobromae, Phomopsis caricae-papayae Fetrak&Cif., Corynespora cassiicola, Phytophthora capsica, Pythium aphanidermatum (Edson) Fitzp, Corynespora sp., Fusarium graminearum, Verticillium dahlia, Pestalotiopsis microspora, and two species of plant pathogenic bacteria including Xanthomonas oryzae pv. oryzae and Ralstonia solanacearum. The bioactivity test results of the compound against agricultural pathogens show that actinomycin D possesses inhibitory activity against the growth of these tested phytopathogenic fungi and bacteria. among which, actinomycin D has the most potent inhibitory activity against the plant pathogenic fungi Lasiodiplodia theobromae, Phomopsis caricae-papayae Fetrak&Cif., Fusarium graminearum and Phytophthora capsica, with inhibitory rate of (60.09 ± 0.66)%, (48.82 ± 0.66)%, (46.47 ± 1.14)% and (44.13 ± 0.66)% , respectively. In addition, actinomycin D displays strong antibacterial activity on the plant pathogenic bacteria Xanthomonas oryzae pv. oryzae and Ralstonia solanacearum with bacteriostatic diameter at (36.00 ± 0.82) mm and (15.00 ± 0.47) mm, respectively. These results provide new compounds and bacteria resources for the development of high-efficiency biocontrol agents for agricultural disease control.