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<p>Nine endophytic bacterial strains were isolated from the leaves of <i>Palaquium amboinense</i> to evaluate their bioactive potential. Among them, isolate DT16 exhibited the strongest antibacterial activity during preliminary screening. Ethyl acetate extracts of DT16 were fractionated into 23 fractions, with Fraction 5 (F5) showing the most consistent biological activity. F5 inhibited <i>Escherichia coli</i>, <i>Pseudomonas aeruginosa</i>, <i>Bacillus subtilis</i>, and <i>Staphylococcus aureus</i> with a minimum inhibitory concentration (MIC) of 625&#xa0;µg/mL. The fraction significantly (<i>p</i> &lt; 0.05) inhibited biofilm formation and reduced preformed biofilm cells, particularly in <i>B. subtilis</i>. Antioxidant activity was demonstrated with half maximal inhibitory concentration (IC₅₀) values of 89.31&#xa0;µg/mL in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and 71.51&#xa0;µg/mL in the 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay. Cytotoxicity assays showed selective reduction of MCF-7 breast cancer cell viability with an IC₅₀ of 57.19&#xa0;µg/mL. Liquid chromatography–tandem mass spectrometry (LC–MS/MS) profiling of F5 revealed two putative metabolites, including taurodeoxycholic acid and azedarachin C. Phylogenetic analysis of the 16&#xa0;S ribosomal ribonucleic acid (16&#xa0;S rRNA) gene identified DT16 as closely related to <i>Bacillus velezensis</i> (&gt; 99% similarity), and partial biosynthetic gene cluster analysis detected fragments of polyketide synthase I (PKS I) and non-ribosomal peptide synthetase (NRPS) genes. These findings indicate that <i>P. amboinense</i>-associated endophytic <i>B. velezensis</i> DT16 represents a promising source of bioactive metabolites with antibacterial, antibiofilm, antioxidant, and cytotoxic activities.</p>

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Bioactive potential of an active fraction from the endophytic Bacillus velezensis strain DT16 associated with Palaquium amboinense

  • 期刊论文

  • 发表日期：

    2026年6月15日

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  • Erma Suryanti,
  • Datu Muhammad Cordova,
  • Aliya Azkia Zahra,
  • Jepri Agung Priyanto,
  • Rose Malina Annuur,
  • Zetryana Puteri Tachrim,
  • Rizna Triana Dewi,
  • Vera Permatasari,
  • Gian Primahana,
  • Adi Yulandi,
  • Nur Fitriana,
  • Dedi Noviendri,
  • Bantari Wisynu Kusuma Wardhani,
  • Muhammad Eka Prastya

摘要

Nine endophytic bacterial strains were isolated from the leaves of Palaquium amboinense to evaluate their bioactive potential. Among them, isolate DT16 exhibited the strongest antibacterial activity during preliminary screening. Ethyl acetate extracts of DT16 were fractionated into 23 fractions, with Fraction 5 (F5) showing the most consistent biological activity. F5 inhibited Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Staphylococcus aureus with a minimum inhibitory concentration (MIC) of 625 µg/mL. The fraction significantly (p < 0.05) inhibited biofilm formation and reduced preformed biofilm cells, particularly in B. subtilis. Antioxidant activity was demonstrated with half maximal inhibitory concentration (IC₅₀) values of 89.31 µg/mL in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and 71.51 µg/mL in the 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay. Cytotoxicity assays showed selective reduction of MCF-7 breast cancer cell viability with an IC₅₀ of 57.19 µg/mL. Liquid chromatography–tandem mass spectrometry (LC–MS/MS) profiling of F5 revealed two putative metabolites, including taurodeoxycholic acid and azedarachin C. Phylogenetic analysis of the 16 S ribosomal ribonucleic acid (16 S rRNA) gene identified DT16 as closely related to Bacillus velezensis (> 99% similarity), and partial biosynthetic gene cluster analysis detected fragments of polyketide synthase I (PKS I) and non-ribosomal peptide synthetase (NRPS) genes. These findings indicate that P. amboinense-associated endophytic B. velezensis DT16 represents a promising source of bioactive metabolites with antibacterial, antibiofilm, antioxidant, and cytotoxic activities.