Abstract
BackgroundCytinus is small genus of endophytic parasitic plants distributed in South Africa, Madagascar, and in the Mediterranean region. In the latter area, two species occur, Cytinus hypocistis and C. ruber, distinguished by both morphological characters and ecological traits. We characterized the ethanolic and aqueous extracts obtained from the inflorescences of C. hypocistis and C. ruber collected in Sardinia, Italy, and explored their tannin content, antioxidant properties and antimicrobial activities.MethodsTotal phenolic contents were determined by Folin-Ciocalteu spectrophotometric method. Tannin content was determined by HPLC. Antioxidant activity of the extracts was tested with both electron transfer-based (FRAP, TEAC, DPPH) and spectrophotometric HAT methods (ORAC-PYR). The antimicrobial activities of extracts/compounds were evaluated using the broth microdilution method. The bactericidal activity was evaluated using the time-kill method. Biofilm formation was evaluated by crystal violet (CV) staining assay.ResultsCharacterization of the tannin profile of C. hypocistis and C. ruber revealed a significant amount of gallotannins, in particular 1-O-galloyl-β-D-glucose. In addition, pentagalloyl-O-β-D-glucose was present in all extracts, reaching the concentration of 0.117 g/kg in the ethanolic extract of C. hypocistis. C. hypocistis extracts displayed a strongest antioxidant activity than C. ruber extracts. Three Gram-positive bacterial species tested (Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecium) resulted sensitive to both Cytinus extracts, with MICs ranging from 125 to 500 μg/ml for aqueous extracts and from 31.25 to 250 μg/ml for ethanolic extracts; on the contrary, Gram-negative strains (Pseudomonas aeruginosa and Klebsiella pneumoniae) were not affected by Cytinus extracts. Intriguingly, we observed the suppressive activity of ethanolic extracts of C. hypocistis and C. ruber on biofilm formation of S. epidermidis. Experiments performed with synthetic compounds indicated that pentagalloyl-O-β-D-glucose is likely to be one of the active antimicrobial components of Cytinus extracts.ConclusionsThese findings show that Cytinus extracts have antimicrobial and antioxidant activities, suggesting a possible application of Cytinus as sources of natural antimicrobials and antioxidants.
Highlights
Cytinus is small genus of endophytic parasitic plants distributed in South Africa, Madagascar, and in the Mediterranean region
C. hypocistis extracts displayed a strongest antioxidant activity than C. ruber extracts, both when results were expressed as Trolox Equivalents and as IC50 (Table 1)
Anti-biofilm activity of Cytinus extracts against S. epidermidis we investigated the ability of C. hypocistis and C. ruber extracts as well as of the two synthetic phytochemicals 1-O-galloyl-β-D-glucose and penta-O-galloylβ-D-glucose to inhibit the formation of biofilms of S. epidermidis, one of the major nosocomial pathogens, often involved in medical device-associated infections [27]
Summary
Cytinus is small genus of endophytic parasitic plants distributed in South Africa, Madagascar, and in the Mediterranean region. In the latter area, two species occur, Cytinus hypocistis and C. ruber, distinguished by both morphological characters and ecological traits. Cytinus (Cytinaceae) is a small genus of holoparasitic, nonchlorophyllic plants, with eight recognized species [4]. It grows endophytically, within the tissues of the host plant: flowers are the only visible part, when they emerge from host tissues during the reproductive period (Fig. 1). In the Mediterranean area, Cytinus parasitize the roots of two genera of shrub plants, Cistus and Halimium, both belonging to the family Cistaceae [7]
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