Extraction, Characterization, and Efficacy of Rosmarinic and Carnosic Acids as Natural Preservatives in Enhancing the Shelf Life of Food Models and Nephroprotective Potential

The demand for natural alternatives to synthetic preservatives has intensified owing to health concerns and consumer preference for clean-label products. Rosmarinic acid (RA) and carnosic acid (CA), prominent phenolic compounds found in Melissa officinalis (lemon balm) and Rosmarinus officinalis (rosemary), respectively, are promising candidates owing to their potent antioxidant and antimicrobial properties. This study aimed to develop optimized extraction protocols for high-purity RA and CA, evaluate their efficacy as natural preservatives in various food models, and investigate the nutraceutical potential of RA. Sequential extraction and purification protocols utilizing aqueous and ethanol-water solvents, acidification, and solvent partitioning were employed. The identity and purity of the isolated compounds were confirmed using HPLC, LC-MS, NMR, and ATR-FTIR. Antioxidant activity was assessed using the DPPH assay. The preservative efficacy was evaluated in cookies, granules, and a cocoa beverage through microbiological analysis (NIS 554:2015) and accelerated shelf-life testing. The nephroprotective effect of RA was investigated using a gentamicin-induced rat model of kidney toxicity. The optimized methods yielded high-purity RA (75 ± 2.1% yield, 85 ± 3.2% purity) and CA (86 ± 1.8% yield, 97 ± 2.7% purity) extracts. CA demonstrated superior antimicrobial activity, reducing total viable bacterial counts in food models to 10 CFU/g, which is a tenfold greater reduction than that of RA (100 CFU/g). Both compounds significantly extended the product shelf life, with CA-fortified granules achieving a predicted shelf life of 5 years compared to 3 months for the controls. In vivo, RA exhibited significant nephroprotection, reducing oxidative stress biomarkers and histopathological damage without toxicity at doses ≤100 mg/kg. RA and CA are effective, safe, and scalable natural preservatives. Carnosic acid, in particular, demonstrates superior yield, purity, antimicrobial efficacy, and shelf-life extension, making it a highly promising candidate for industrial applications in food preservation and nutraceuticals.