Antioxidant activity and polyphenol content of endemic plant species Centaurea ragusina L.
The genus of Centaurea (Asteraceae) represents an attractive source of bioactive substances . The goal of this work is to determine polyphenol content and antioxidant activity in endemic Croatian plant species Centaurea ragusina L. cultivated in vitro (½MS 2.9 µM GA3+0.5 µM BA and ½MS 2.5 µM IBA)  and collected at natural habitats (Katalinić brig – K and Sustipan – S). To clarify biological activity of C. ragusina, interactions of extracts with double stranded polynucleotides (poly A – poly U and ctDNA) were studied. The highest level of total phenols, flavonoids and flavonols was determined in calli ethanol/aqueous extracts cultivated in vitro (2.9 µM GA3 + 0.5 µM BA) while the highest value of hydroxycinnamic acids and proanthocyanidins was detected in ethanol/aqueous extracts of leaves after acclimatization from culture media (½MS 2.5 µM IBA). Significant antioxidant activity measured by DPPH and ABTS methods was observed in almost all extracts with respect to gallic acid as a standard. Extracts of leaves after acclimatization showed the highest stabilization on poly A – poly U (18.36) and ctDNA (5.75) evaluated by changing of melting temperature of the polynucleotide (ΔTm). Results of circular dichroism (CD spectroscopy) indicate significant impact of all tested extracts on the conformation of both polynucleotides. The results obtained suggest that the plant species C. ragusina grown in vitro can be efficiently used as a potential source of polyphenols and antioxidants in food, pharmacological and cosmetics industry as it is equally rich with phytochemicals as its wild grown counterparts.
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