Exploring Phlomis crinita extracts: HPLC analysis, phenolic content, antioxidant and antimicrobial potentials

Phlomis crinita Cav. (P. crinita), known as " Khayat el-djerah " in Algerian folk medicine, is used for wound healing and abdominal pain relief. This study assessed the phytochemical profile, phenolic content, antimicrobial activity against five Gram-negative and three Gram-positive clinical bacterial strains, as well as in vitro antioxidant activity of hydroethanolic extracts from leaves (HLE), flowers (HFE), and rhizomes (HRE) of P. crinita. Fifteen phenolic compounds such as four flavonoids, trans-cinnamic acid, six cinnamic acid derivatives, and four benzoic acid derivatives were identified for the first time in P. crinita by HPLC-DAD, with quantitative differences among the analyzed parts. HRE exhibited high levels of total phenolics (262.97 ± 16.2 μg GAE/mg DW) and flavonoids (71.87 ± 3.25 μg QE/mg DW), while HLE had the highest flavonols content (18.89 ± 5.12 μg QE/mg DW). All extracts demonstrated strong antioxidant properties. HLE exhibited the highest potency, with IC50 values of 15.46 ± 0.45 µg/mL (DPPH) and 11.71 ± 0.50 µg/mL (ABTS). HLE exhibited good reducing power (FRAP A0.5 = 40.07 ± 2.82 µg/mL), while HRE showed the best reducing power (Phenanthroline A0.5 = 7.88 ± 1.63 µg/mL). All extracts revealed broad-spectrum antibacterial effects, and HRE exhibited the most potent activity against Enterococcus faecalis, with a minimum inhibitory concentration (MIC) value of 1.25 mg/mL. These results showed that P. crinita could be useful as source of bioactive compounds for pharmaceutical and food industry.