**Dongbo Xu 1, Erli Tian 1, Fandong Kong <sup>2</sup> and Kui Hong 1,\***


Received: 17 April 2020; Accepted: 12 May 2020; Published: 13 May 2020

**Abstract:** Five new compounds 15*R*-17,18-dehydroxantholipin (**1**), (*3E*,*5E*,*7E*)-3-methyldeca-3,5,7 triene-2,9-dione (**2**) and qinlactone A–C (**3**–**5**) were identified from mangrove *Streptomyces qinglanensis* 172205 with "genetic dereplication," which deleted the highly expressed secondary metabolite-enterocin biosynthetic gene cluster. The chemical structures were established by spectroscopic methods, and the absolute configurations were determined by electronic circular dichroism (ECD). Compound **1** exhibited strong anti-microbial and antiproliferative bioactivities, while compounds **2**–**4** showed weak antiproliferative activities.

**Keywords:** mangrove *Streptomyces*; genetic dereplication; anti-microbial; antiproliferative
