Extracellular Metabolites of Clove-Endophytic Bacteria, Niallia nealsonii DCL1, Exhibit Potential Cellular Antioxidant and Antiaging Activities

The clove plant, Syzygium aromaticum L., is a highly valued spice in Indonesia, recognized for its extensive applications in food preservation and medicinal uses. In a prior study, six endophytic bacteria were successfully isolated from clove leaves. One of these isolates, designated as DCL1, is a Gram-positive bacterium identified as Niallia nealsonii. This study aimed to determine the antioxidant and antiaging properties of the extracellular metabolite of DCL1. Extracellular metabolites were extracted with ethyl acetate and evaluated for antioxidant activity via the DPPH assay. Total phenolic and flavonoid compounds were also quantified with further metabolilte profiling using Liquid Chromatography Tandem-Mass Spectrometry (LC-MS/MS) analysis. Further study of antiaging activity was assayed using yeast model Schizosacchromyces pombe. The extract from N. nealsonii DCL1 cultures harvested at 28 and 40 hours yielded 0.01% and 0.009%, respectively. Our findings indicate that the 40-hour extract contains higher levels of phenolics (93.54 mg gallic acid equivalents/g extract) and flavonoids (12.09 mg quercetin equivalents/g extract) compared to the 28-hour extract. Additionally, the 40-hour extract exhibited greater antioxidant activity than the 28-hour extract, as demonstrated by DPPH (IC50 222 µg/mL) and ABTS (IC50 511.43 µg/mL) assays. Moreover, the 40-hour extract significantly prolonged the viability of S. pombe, suggesting its potential as an anti-aging agent. LC-MS/MS analysis identified several potential bioactive compounds, including gallic acid and N-carbamoyl-2,3-dihydroxybenzamide, which may contribute to its bioactivity. Ultimately, our study indicates that DCL1 40-h extract showed antiaging potential, which is promising as source and formulation of biopharmaceutical or cosmeceutical products.