Streptomyces sp. MUM273b: A mangrove-derived potential source for antioxidant and UVB radiation protectants

Abstract

Microbial natural products serve as a good source for antioxidants. The mangrove-derived Streptomyces bacteria have been evidenced to produce antioxidative compounds. This study reports the isolation of Streptomyces sp. MUM273b from mangrove soil that may serve as a promising source of antioxidants and UV-protective agents. Identification and characterization methods determine that strain MUM273b belongs to the genus Streptomyces. The MUM273b extract exhibits antioxidant activities, including DPPH, ABTS, and superoxide radical scavenging activities and also metal-chelating activity. The MUM273b extract was also shown to inhibit the production of malondialdehyde in metal-induced lipid peroxidation. Strong correlation between the antioxidant activities and the total phenolic content of MUM273b extract was shown. In addition, MUM273b extract exhibited cytoprotective effect on the UVB-induced cell death in HaCaT keratinocytes. Gas chromatography-mass spectrometry analysis detected phenolics, pyrrole, pyrazine, ester, and cyclic dipeptides in MUM273b extract. In summary, Streptomyces MUM273b extract portrays an exciting avenue for future antioxidative drugs and cosmeceuticals development.

Keywords: Streptomyces; UV-protective; antioxidant; cosmeceutical; mangrove.

Figure 1

Neighbor‐joining phylogenetic tree based on the almost complete 16S rRNA sequences that shows the evolutionary relationships between the strain MUM273b (1406 bp) and representatives of some other related taxa. Bootstrap values (>50%) based on 1,000 re‐sampled datasets are shown at branch nodes. Bar, 0.005 substitutions per site

Figure 2

The scanning electron micrographs of Streptomyces sp. MUM273b. It appears as smooth filaments and branch to form a network of filaments called mycelium

Figure 3

Effect of MUM273b extract against lipid peroxidation induced by Fe²⁺. MDA level was quantified using TBARS assay. All data are presented as mean ± SD (n = 3). *indicates p < 0.05 between control (without extract) and MUM273b extract added samples. MDA, malondialdehyde; TBARS, thiobarbituric acid reactive species

Figure 4

Protective effect of MUM273b extract against UVB‐induced cytotoxicity in HaCaT keratinocytes. (a) The HaCaT cells were exposed to UVB (50 mJ/cm²) in the presence of MUM273b extract at different concentrations. The cell viability was measured by MTT assay after 24 hr. All data are present as mean ± SD (n = 5). # indicates p < 0.05 between control (without UVB) and cells exposed to UVB (50 mJ/cm²). *indicates p < 0.05 between cells (without extract) and MUM273b extract‐treated cells after UVB exposure. (b) The morphological changes of HaCaT cells observed under phase‐contrast microscopy (×100)

Figure 5

Chemical structures of constituents detected in MUM273b extract