Phlomis crinita Cav. From Algeria: A source of bioactive compounds possessing antioxidant and wound healing activities

Phlomis crinita Cav. (Lamiaceae), locally known as "El Khayata" or "Kayat El Adjarah", is traditionally used in Algeria for its wound-healing properties.

Investigate, for the first time, the phytochemical profile, safety, antioxidant and wound-healing activities of the flowering tops methanolic extract of P. crinita (PCME) collected from Bouira Province in the North of Algeria.

Preliminary phytochemical assays were carried out on PCME to quantify the main classes of bioactive compounds, such as total phenols, flavonoids, and tannins. An in-depth LC-DAD-ESI-MS analysis was carried out to elucidate the phytochemical profile of this plant species. Antioxidant activity was investigated by several colorimetric and fluorimetric assays (DPPH, TEAC, FRAP, ORAC, β-carotene bleaching and ferrozine assay). The acute oral toxicity of PCME (2000 mg/kg b.w.) was tested in vivo on Swiss albino mice, whereas the acute dermal toxicity and wound-healing properties of the PCME ointment (1-5% PCMO) were tested in vivo on Wistar albino rats. Biochemical and histological analyses were carried out on biological samples.

The phytochemical screening highlighted a high content of phenolic compounds (175.49 ± 0.8 mg of gallic acid equivalents/g of dry extract), mainly flavonoids (82.28 ± 0.44 mg of quercetin equivalents/g of dry extract). Fifty-seven compounds were identified by LC-DAD-ESI-MS analysis, belonging mainly to the class of flavones (32.27%), with luteolin 7-(6″-acetylglucoside) as the most abundant compound and phenolic acids (32.54%), with salvianolic acid C as the most abundant compound. A conspicuous presence of phenylethanoids (15.26%) was also found, of which the major constituent is forsythoside B. PCME showed a strong antioxidant activity with half-inhibitory activity (IC₅₀) ranging from 1.88 to 37.88 μg/mL and a moderate iron chelating activity (IC₅₀ 327.44 μg/mL). PCME appears to be safe with Lethal Dose 50 (LD₅₀) ≥ 2000 mg/kg b.w. No mortality or toxicity signs, including any statistically significant changes in body weight gain and relative organs' weight with respect to the control group, were recorded. A significant (p < 0.001) wound contraction was observed in the 5% PCMO-treated group with respect to the untreated and petroleum jelly groups between 8 and 20 days, whereas no statistically significant results were observed at the two lower doses (1 and 2% PCMO). In addition, the 5% PCMO-treated group showed a statistically significant (p < 0.05) wound healing activity with respect to the reference drug-treated group, showing, at the end of the study, the highest wound contraction percentage (88.00 ± 0.16%).

PCME was safe and showed strong antioxidant and wound-healing properties, suggesting new interesting pharmaceutical applications for P. crinita based on its traditional use.