Morphological Characterization and Antioxidant Activity of Actinobacteria from Xylocarpus granatum Growing in Mangrove Habitat

Abstract

Xylocarpus granatum produces various bioactive compounds with diverse biological activities, one of them as an antioxidant. Endophytic actinobacteria can also produce bioactive compounds. This study aimed to explore the existence of the endophytic actinobacteria of X. granatum fruit and determine its antioxidant activity. The research method was carried out by isolating the endophytic actinobacteria from the fruit using selective media Humic Acid (HV). Furthermore, characterizing the obtained isolates using four different media, namely YSA, ISP2, ISP3, and ISP4, measured antioxidant activity for actinobacterial supernatants and actinobacterial ethyl acetate extracts using the DPPH method. The results showed that from X. granatum, 15 isolates of endophytic actinobacteria were obtained from fruit, seeds, and leaves. Endophytic actinobacteria isolates from X. granatum showed different colors of aerial mycelium, substrate mycelium, and spore chain type. XGF11, XGF12, and XGF4 isolates produced high antioxidant activity of the supernatant; 57.30%, 49.77%, and 41.90% inhibition, respectively. The antioxidant capacity of XGF12 ethyl acetate extract was 501.60 μg AEAC/mg extract and 465.47 μg AEAC/mg extract for XGF11 ethyl acetate extract. Based on 16S rRNA gene analysis, isolates XGF12 and XGF11 showed similarities with Streptomyces xylanilyticus, and isolated XGF4 showed similarities with Brevibacterium sediminis.