BIODIVERSITAS ISSN: 1412-033X Volume 23, Number 9, September 2022 E-ISSN: 2085-4722 Pages: 4730-4737 DOI: 10.13057/biodiv/d230940 An orange pigment from the marine bacterium Paracoccus haeundaensis SAB E11 as a prospective source of natural antioxidants HERMAWATY ABUBAKAR 1 , RIKA INDRI ASTUTI 1 , SRI LISTYOWATI 1 , IRMANIDA BATUBARA 2,3 , ARIS TRI WAHYUDI 1, 1 Department of Biology, Faculty of Mathematics and Natural Sciences, Institut Pertanian Bogor. Jl. Raya Dramaga, Bogor 16680, West Java, Indonesia. Tel./Fax.: 62-251-8622833,  email: ariswa@apps.ipb.ac.id 2 Department of Chemistry, Faculty of Mathematics and Natural Sciences, Institut Pertanian Bogor. Jl. Raya Dramaga, Bogor 16680, West Java, Indonesia 3 Trophical Biopharmaca Research Centre, Science and Technology Park, Institut Pertanian Bogor. Jl. Taman Kencana no. 3, Bogor 16128, West Java, Indonesia Manuscript received: 11 July 2022. Revision accepted: 9 September 2022. Abstract. Abubakar H, Astuti RI, Listyowati S, Batubara I, Wahyudi AT. 2022. An orange pigment from the marine bacterium Paracoccus haeundaensis SAB E11 as a prospective source of natural antioxidants. Biodiversitas 23: 4730-4737. Bacterial pigment extracts are the source of many natural antioxidant substances. The present study aimed to assess the antioxidant activity of an orange pigment derived from a marine bacterium, identified as Paracoccus haeundaensis SAB E11, analyzed by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2-azino-bis(ethylbenzothiazoline-6-sulfonic acid) (ABTS). Methanol-pigmented crude extract of P. haeundaensis SAB E11 exhibited the best DPPH scavenging activity with an IC50 value of 54.7 g/mL, while the n-hexane crude pigment extract of the bacterium reduced ABTS optimally with an IC50 value of 24.46 g/mL. The analysis of antioxidant compounds in P. haeundaensis SAB E11 was identified by combining liquid chromatography with tandem mass spectrometry (LCMS/MS). The five antioxidant compounds from methanol and n-hexane crude pigment extract of P. haeundaensis SAB E11 have been detected. Polyphenols were found to be the major compound, such as 3,5,3’,4’-tetrahydroxystilbene, scopoletin, and liquiritigenin. The other compounds were dihydroactinidiolide (terpenes) and ricinoleic acid (a fatty acid compound). The orange-colored extract of marine bacterium P. haeundaensis SAB E11 could be promising pharmacological capabilities as an antioxidant. Keywords: ABTS, antioxidant, DPPH, marine bacterium, pigment extract INTRODUCTION Cell metabolism, poor lifestyle, and environmental condition are prominent aspects of presenting oxidants in the cells. Oxidants are free radicals raised from oxygen, nitrogen, and sulfur that generate molecules with unpaired electrons. Consequently, the molecules are unstable and chemically reactive with other molecules to form unwanted chain reactions. Reactive Oxygen Species (ROS) are typically produced as metabolic cells, including hydroxyl radicals, hydrogen peroxide, nitric acid, or superoxide anions. However, ROS molecules are reactive to other macromolecules such as protein, lipid, and nucleic acid, causing cell damage (Ali et al. 2020; Andrés et al. 2021). Antioxidants are produced in cells to prevent oxidation by neutralizing free radicals with donating electrons. Nevertheless, antioxidants are overpowered by the increased number of free radicals resulting in oxidative stress (di Meo and Venditti 2020). Several cases have shown that oxidative stress causes degenerative diseases such as diabetes mellitus, Alzheimer's, cancer, and hypertension (Nandi et al. 2019). Nowadays, plants are widely consumed as a source of natural antioxidants. However, many studies show that bacteria i.e. tiny organisms, produce antioxidant compounds. In addition, bacteria have a short life cycle, ease of culture, and easy subject to genetically engineering indicating that bacteria are potential sources of antioxidants. Bacteria produce antioxidant compounds such as phenolic, pigments, polysaccharides, and organic acids (Milke et al. 2018; Hamidi et al. 2019; Pérez-gálvez et al. 2020). Derivatives of polyphenolic and pigments are reported to have the highest antioxidant activity. Several polyphenolic compounds carry antioxidant activities. The compounds are simple phenols, phenolic acids, hydroxycinnamic acid, coumarins, naphthoquinones, xanthones, stilbenes, anthraquinones, flavonoids, and lignins. The intensity of antioxidant activity of the polyphenol complex is related to the degree of polymerization of the polyphenol. In general, lower levels of polymerization react with more excellent antioxidant activity and present other bioactive activities (Rudra et al. 2021). Another interesting antioxidant compound is pigment, a dye molecule that absorbs specific wavelengths of light and reflects the visible light spectrum in the wavelength range between 380-750 nm (Ramesh et al. 2019; Kusmita et al. 2021). The pigment colors of the bacterial cells play an essential role in physiological and molecular functions. In heterotrophic bacteria, the pigment plays a role in bacterial growth sustainability in the habitat. A pigment such as carotenoids can protect bacterial cell