Objective This study aimed to evaluate the phenolic and flavonoid composition of the hydro-ethanolic extract of Psidium guajava L. leaves harvested from the El Oued region (southeastern Algeria) and to investigate its various biological activities. Methods Dried P. guajava leaves were defatted with petroleum ether and then extracted with ethanol by cold maceration using 50% aqueous. Total phenolic content (TPC) and total flavonoid content (TFC) were quantified using standard spectrophotometric methods, phenolic compounds were identified using high-performance liquid chromatography coupled with diode-array detection (HPLC-DAD). The extract's antioxidant activity was determined by DPPH radical scavenging assay. In vitro assays were also conducted to evaluate anti-hemolytic, antibacterial (against Pseudomonas aeruginosa , Escherichia coli , Staphylococcus aureus , and Bacillus subtilis ), anti-inflammatory (based on bovine serum albumin BSA denaturation), and α-amylase inhibitory activities. Results The results that the extract contained high levels of total phenolics and flavonoids, HPLC-DAD identified major compounds such as gallic acid and quercetin. The extract demonstrated potent antioxidant activity (IC 50 = 17.24 ± 0.01 µg/mL), which was less effective than that of standard ascorbic acid. However, it showed superior α-amylase inhibitory activity compared to acarbose (IC 50 = 168.32 ± 1.12 vs 299.26 ± 17.81 µg/mL). Additionally, the extract exhibited moderate anti-inflammatory activity (IC 50 = 459.14 ± 27.49 µg/ml) compared to aspirin and moderate anti-hemolytic activity compared to vitamin E, antibacterial activity was more pronounced against Gram-positive strains. Conclusion The findings highlight the therapeutic potential of P. guajava leaves as a natural source of bioactive compounds with antioxidant, anti-inflammatory, antibacterial, and antihyperglycemic properties.
Seghieri et al. (Wed,) studied this question.