Insecticidal Endostemonines A-J Produced by Endophytic Streptomyces from Stemona sessilifolia.

The discovery of new, safe, and effective pesticides is one of the main means for modern crop protection and parasitic disease control. During the search for new insecticidal secondary metabolites from endophytes in Stemona sessilifolia (a traditional Chinese medicine with a long history as an insecticide), 10 new insecticidal endostemonines A-J (1-10) were identified from an endophytic Streptomyces sp. BS-1. Their structures were determined by comprehensive spectroscopic analysis. Endostemonines A-J represent the first reported naturally occurring pyrrole-2-carboxylic ester derivatives, which consisted of different fatty acid chains at the C-2 of pyrrole ring were produced by traditional Chinese medicine endophytic microbes. All new tested compounds exhibited strong lethal activity against Aphis gossypii (LC50 value range of 3.55-32.00 mg/L after 72 h). This research highlighted the discovery of pesticide natural products from insecticidal medicinal plant endophytes for the first time, paving a new pathway for the development of pest control.

[Isolation, classification and biosynthetic potential of endophytic actinomycetes from Stemona].

OBJECTIVE: To isolate endophytic actinomycetes from earthnut samples of Stemona tuberosa Lour. collected from Xishuangbanna, Yunnan Province, and to study the classification, antimicrobial activity and secondary metabolic potential of the isolates. METHODS: Samples were treated by a well-established surface-sterilized procedure, and plated on four selective media. The isolates were identified by morphology and 16S rRNA gene sequence analysis. Antimicrobial activity of the isolates was tested using agar diffusion method. Secondary metabolite genes of PKS/NRPS and halogense were detected by PCR amplification. HPLC-UV and VIS-ESI-MS/MS were used to analyze the fermentation product. RESULTS: We obtained 18 actinomycete isolates from 6 Stemona earthnut samples. The isolates belonged to 4 genera, Streptomyces, Pseudonocardia, Micromonospora and Methylobacterium, and 10 of them were streptomycetes. The isolates also showed distinguish positive rates of antibacterial activity and secondary metabolite genes. Of them 13 strains showed antimicrobial activity against Staphlococcus aureus and/or Pseudomonas aeruginosa. Of them 17 isolates were positive for PKS/NRPS genes, and 8 strains were positive for halogenase gene. Moreover, the representative halogenase gene- positive strain produced metabolites that had typical MS peaks of halogen absorption. CONCLUSION: Based on the results of this study, the endophytic actinomycetes from Stemona, dominant by Streptomyces and Micromonospora, have good secondary metabolic potential and could serve as a promising resource for bioactive metabolite discovery in the future.

11-Hydroxymonocerin from the plant endophytic fungus Exserohilum rostratum.

A new analogue of monocerin, 11-hydroxymonocerin (2), along with monocerin (1) and 12-hydroxymonocerin (3) were isolated from cultures of Exserohilum rostratum, a fungal strain endophytic in Stemona sp. The structure of 2 was determined by analysis of NMR and MS data and by comparison of spectroscopic data to those of 1. Monocerin (1) and 11-hydroxymonocerin (2) displayed activity against Plasmodium falciparum (K1, multidrug-resistant strain) with IC50 values of 0.68 and 7.70 microM, respectively. None of the compounds were cytotoxic against any of the tumor cell lines tested.

Isolation and identification of an endophytic strain EJS-3 producing novel fibrinolytic enzymes.

An endophytic strain EJS-3, which produces a novel fibrinolytic enzyme, was screened from root tissue of Stemona japonica (Blume) Miq, a chinese traditional medicine. This strain was identified as Paenibacillus polymyxa (DQ120522) by morphological, physiological, and biochemical tests and 16S rRNA gene sequence analysis. Two serine-type fibrinolytic enzymes with a relative molecular weight about 118 and 49 kDa, respectively, which are larger than known fibrinolytic enzymes, were found by the SDS-fibrin zymogram or by fibrin-inhibitor zymography gels. No work on P. polymyxa-producing fibrinolytic enzymes has been reported.