Huoshanmycins A‒C, New Polyketide Dimers Produced by Endophytic Streptomyces sp. HS-3-L-1 From Dendrobium huoshanense.

Youjuan Zhu,Tian Xie,Simin Li,Yichao Kong,Yu Hong,Ling Zhang,Yang Hu,Xiachang Wang,Xiabin Chen,Shurong Hou

doi:10.3389/fchem.2021.807508

Youjuan Zhu, Tian Xie + Show 8 more

Open Access

https://doi.org/10.3389/fchem.2021.807508

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Abstract

Three new polyketide dimers named huoshanmycins A‒C (1–3) were isolated from a plant endophytic Streptomyces sp. HS-3-L-1 in the leaf of Dendrobium huoshanense, which was collected from the Cultivation base in Jiuxianzun Huoshanshihu Co., Ltd. The dimeric structures of huoshanmycins were composed of unusual polyketides SEK43, SEK15, or UWM4, with a unique methylene linkage. Their structures were elucidated through comprehensive 1D-/2D-NMR and HRESIMS spectroscopic data analysis. The cytotoxicity against MV4-11 human leukemia cell by the Cell Counting Kit-8 (CCK8) method was evaluated using isolated compounds with triptolide as positive control (IC50: 1.1 ± 0.4 μM). Huoshanmycins A and B (1, 2) displayed moderate cytotoxicity with IC50 values of 32.9 ± 7.2 and 33.2 ± 6.1 μM, respectively.

Highlights

Dendrobium huoshanense is a perennial epiphytic Orchidaceae herb with important medicinal and ornamental value
Research on D. huoshanense endophytes mainly focuses on the diversity and functions, while not much is known about their secondary metabolites, especially for bacteria
The last four compounds all belong to polyketides, which are derived from a Polyketide Dimers from Endophytic Streptomyces precursor molecule consisting of a chain of alternating ketone and methylene groups

Summary

INTRODUCTION

Dendrobium huoshanense is a perennial epiphytic Orchidaceae herb with important medicinal and ornamental value. Streptomyces is the largest genus of Actinobacteria and characterized by producing complex secondary metabolites. They produce over two-thirds of the clinically useful antibiotics of natural origin (e.g., chloramphenicol, streptomycin, tetracycline, erythromycin, ivermectin, and rifamycin) (Raja and Prabakarana, 2011). As part of an effort to characterize novel natural products from medicinal plants (Wang et al, 2009; Ding et al, 2021; Hu et al, 2021) and their endophytes (Zhao et al, 2020b; Zhao et al, 2020a; Zhu et al, 2021), we report the isolation and characterization of three new polyketide dimers from an endophyte Streptomyces sp. We report the fermentation, extraction, isolation, structural elucidation, and cytotoxic activity of these secondary metabolites

MATERIALS AND METHODS

RESULTS AND DISCUSSION

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