A Novel Cytotoxic Secondary Metabolite from Streptomyces sp. CMDD20H95 through Bioactivity-Guided Fractionation: Its Isolation and Structure Elucidation

Abstract

Cancer is among the leading causes of death worldwide and characterized by spreading uncontrollably growing cells over each different part of the body. Natural products have been a great source of anti-cancer medicinal agents. Many anti-cancer drugs were originated from natural sources. Due to the wide range of structural diversity of natural products, we can discover innovative candidates for the therapeutic application of cancer. In this study, we mainly focused on the discovery of anti-cancer compounds from the secondary metabolites of Streptomyces cavourensis. The strain was isolated from the leaves of the plant Cinnamomum cassia in Hoa Binh province of northern Vietnam. Experiments including cultivation of S. cavourensis, and isolation, purification, structure elucidation of the compound were conducted and bioactive-guided fractionation was carried out according to MTT assay results which show cell viability. First, the crude extract was examined whether it contains anti-cancer compounds through MTT assay. Then, further separation and purification of the active compound using various chromatographic methods, and its biological activity investigation were performed. The structure of the compound was elucidated and confirmed using spectroscopic methods such as Nuclear Magnetic Resonance (NMR) spectroscopy (1H, 13C, COSY, HSQC, HMBC, and ROESY), mass spectrometry, and UV spectrometry. From these data, we obtained the full structure of the compound and named it cavomycin A. In the MTT assay, five cancer cell lines were tested including lung carcinoma cells (A549), prostate carcinoma cells (DU145), colorectal carcinoma cells (HCT116), breast carcinoma cells (MCF7), and pancreatic carcinoma cells (PANC-1). The cells were treated with cavomycin A at different doses (from 50 nM to 100 μM). As a result, cavomycin A showed potent inhibitory activity against the proliferation of all tested cancer cells with IC50 values of around 0.1 μM.

암은 전 세계 주요 사망 원인 중 하나로 신체의 각 부분에 걷잡을 수 없이 세포가 성장하는 것을 특징으로 하는 질병이다. 천연물은 오래전부터 암의 치료 약물의 주요자원으로 사용되었다. 천연물은 광범위한 구조적 다양성을 가지고 있어 이로부터 암 치료에 혁신적인 후보물질을 발견할 수 있다. 본 연구에서는 베트남의 호아빈 지역의 Cinnamomum cassia의 잎으로부터 분리한 Streptomyces cavourensis가 생산한 이차대사산물로부터 항암효과를 갖는 물질을 찾는 연구를 진행하였다. 다양한 크로마토그래피 기법과 화학적 방법으로 S. cavourensis의 배양 추출물을 분리 및 정제하였고 물질의 화학구조는 NMR 분석, 질량 분석, UV 분광법을 이용하여 결정하였다. 분리된 물질은 cavomycin A로 명명하였으며 세포 생존율을 나타내는 MTT assay를 통해 물질의 항암 활성을 확인하였다. MTT assay에는 5가지의 암세포(폐암, 전립선암, 대장암, 유방암, 췌장암)가 사용되었으며 각 세포에 cavomycin A을 다양한 농도 조건(50 nM 부터 100 μM)으로 처리해 물질의 활성을 확인하였다. 그 결과, 암세포에 대한 cavomycin A의 IC50 값이 0.1 μM 이하로 나타났으며 이를 통해 cavomycin A의 잠재적인 항암활성을 확인하였다.