RSM-Optimized Extraction and Evaluation of Bioactivities of Polyphenols From Syzygium jambos (L.) Alston Fruits

Syzygium jambos (L.) Alston fruits, a traditional medicinal species in the Myrtaceae family, are rich in polyphenolic compounds. This study optimized polyphenol extraction from S. jambos fruits using ultrasonic-assisted extraction combined with response surface methodology, achieving a total polyphenol content (TPC) of 31.24 mg/g. To further enrich polyphenols, crude extracts (CEs) were fractionated using solvents of increasing polarity (petroleum ether, dichloromethane, and ethyl acetate). Results showed that the ethyl acetate phase (EAP) had the highest TPC (96.25 mg/g, threefold higher TPC than CE) and strongest antioxidant activity. In addition, polyphenol extracts demonstrated excellent biocompatibility, significant tyrosinase inhibition, and antibacterial activity against Escherichia coli and Staphylococcus aureus, with inhibition zones of 16.2 ± 0.5 and 14.3 ± 0.6 mm at 100 mg/mL. Finally, 41 polyphenolic compounds were identified by liquid chromatography-mass spectrometry (LC-MS) in EAP, including flavonoids (quercetin, isorhamnetin, and rutin), phenolic acids (caffeic acid and ferulic acid), and tannins (corilagin). These results demonstrate the potential of S. jambos polyphenols as natural additives for antioxidant, skin-whitening, and antimicrobial applications.