Cistus incanus L. commercial products as a good source of polyphenols in human diet

- Higher levels of phenolic compounds were found in aqueous extracts of C. incanus.
- Aqueous extracts of C. incanus demonstrate stronger antioxidant activities.
- C. incanus is characterised especially against Gram-positive bacteria.
- Aqueous extracts of C. incanus inhibit growth of C. albicans and C. glabrata.
- The place of origin is a factor in differentiating C. incanus samples.

Recently numerous manufacturers promote herbal infusions and dietary supplements based on the plant Cistus incanus because of its high content of phenolic compounds and strong antioxidant activity. Thus, the aim of this study was to assess the phenolic profile and antioxidant capacity of hydromethanolic and aqueous extracts of commercial C. incanus products. Individual phenolic acids and flavonoids were determined using HPLC, while antioxidant capacities were evaluated by use of scavenging assays of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) and ferric reducing/antioxidant power (FRAP). Total phenolic, flavonoid, phenolic acid and L(+)-ascorbic acid contents were quantified using UV-vis spectrometry, whereas in vitro antimicrobial activities of aqueous extracts of C. incanus were investigated by the broth microdilution technique using 96-well plates. The place of origin was the main factor in differentiating C. incanus samples. The results revealed that aqueous extracts of C. incanus are richer in phenolic compounds and have stronger antioxidant activities than hydromethanolic extracts. Moreover, aqueous extracts revealed antibacterial activities more effective against Gram-positive bacteria, particularly S. aureus (MIC values from 0.5 to 32 mg/mL) and S. epidermidis (MIC values from 0.25 to 8 mg/mL) than Gram-negative bacteria. They were also weak inhibitors of C. albicans and C. glabrata growth (MIC values over 8 mg/mL).