Molecular Identification, Metabolites profiling, Anti-breast cancer, Anti-colorectal cancer, and antioxidant potentials of Streptomyces zaomyceticus AA1 isolated from a remote bat cave in Egypt

Abstract

Cancer is one of the leading causes of death all over the world. Colorectal cancer, and breast cancer are responsible for about 1.5 million deaths in 2018 only. Searching for promising sources of anticancer compounds is a matter of life and death. Actinomycetes are attracting continuous attention due to their ability to produce variety of natural bioactive metabolites. Hence, screening for new actinomycetes isolates was conducted from soil containing bat faeces collected from a remote cave located near Asyut Governorate, Egypt. Isolation plates from the referred locality showed special remarkable predominance of a Streptomycete strain that was assigned as strain AA1. Ethyl acetate extracts of AA1 cultures grown on two different media, ISP2 and starch casein broth, were comparatively evaluated for their in vitro anti-breast cancer, anti-colorectal cancer, as well as antioxidant activities. The results showed an impressive potency of AA1 extracts against colorectal and breast cancers. The extract (200μg/ml) developed from starch casein culture medium of AA1 showed the highest potency (94.0±0.1% cytotoxicity) against HCT116 cell lines of colorectal cancer compared with ISP2 extract (91.98±0.9% cytotoxicity). However, the two extracts showed comparable strong anti-breast cancer activity against MCF7 cell lines where they exerted cytotoxicity of 97.01±0.8% and 96.27±0.2% for extracts developed from ISP2 and starch casein broth media respectively. On the other hand, significant difference in potentialities of the two medium in antioxidant activities was shown. Superiority of ISP2 over starch casein was clearly revealed where they recorded DPPH scavenging percentage of 53.5±3.4% and 36.5±4.4% respectively. GC-MS analysis of both extracts revealed the presence of 36 different compounds and emphasized the effect of culture medium on qualitative and quantitative distribution of metabolites. This promising isolate was molecularly identified using 16S rRNA gene sequencing and was deposited in NCBI GenBank as MN567306 under the name Streptomyces zaomyceticus strain AA1.