Chemical characterization, antioxidant, antimicrobial and cytotoxic potential of Cistus creticus subsp. creticus and C. creticus subsp. eriocephalus (Cistaceae) extracts

The traditional medicinal use of Cistus (Cistaceae) mainly involves an aromatic oleoresin known as labdanum, primarily used for treating infections and promoting wound healing. This study aimed to investigate the chemical composition, antioxidant, antimicrobial, and cytotoxic activities of ethanol and ethyl acetate extracts from the aerial parts of two Cistus creticus subspecies (C. creticus subsp. creticus and C. creticus subsp. eriocephalus).

Phytochemical profiling was conducted using UHPLC-MS/MS. Antioxidant activity was evaluated by DPPH, ABTS, and β-carotene bleaching assays, antimicrobial activity by a microdilution method against twelve bacterial and one yeast species, and cytotoxicity by the MTT assay. In addition, selectivity of the antimicrobial and anticancer effect was calculated.

A total of 23 phytochemicals, mainly phenolic acids and flavonoids, were identified and quantified. Ethanol extracts yielded higher amounts, with gallocatechin as the major compound, while the main constituents in ethyl acetate extracts were isorhamnetin and gallic acid. All extracts showed significant antioxidant activity, with IC₅₀ values ranging from 0.12 to 1.89 mg/mL for DPPH, 0.15 to 2.17 mg/mL for ABTS, and 0.30 to 5.04 mg/mL for β-carotene bleaching, with ethanol extracts consistently more active. A microdilution assay revealed promising antimicrobial activity, with Streptococcus pyogenes (MIC 0.10–10.00 mg/mL) and Staphylococcus aureus (MIC 0.15–5.00 mg/mL) among the most sensitive strains. The MTT assay showed that the survival rates of normal fetal lung fibroblasts (MRC-5) and melanoma cells (Hs294T) treated with the extracts (at concentrations of 0.0625–0.25 mg/mL) ranged from 10.83% to 100.85% and from 6.51% to 100.33%, respectively.

Overall, these findings provide a solid basis for further research on the pharmaceutical potential of C. creticus as an underutilised source of phenolic compounds.