EXAMINATION OF THE ANTIOXIDANT ACTIVITY OFHABERLEA RHODOPENSISLEAF EXTRACTS AND THEIR PHENOLIC CONSTITUENTS

Abstract

ABSTRACT The present study investigated Haberlea rhodopensis Friv. – a less-explored Balkan endemic plant. The purpose was to determine the total phenolic content and antioxidant activity of alcohol extracts derived from the leaves of H. rhodopensis Friv. by applying reliable methods. The phenolic concentration in the examined extracts, calculated as mg gallic acid equivalent (GAE)/g leaf dry weight (DW), ranged from 99.03 to 151.24 mg GAE/g DW. The results from the total phenolics assay and the antioxidant activity tests were significantly correlated. The methanol and 70% ethanol extracts, which had the highest total phenolic content values (151.24 and 150.67 mg GAE/g DW, respectively), ranked the highest radical scavenging activity according to the 2,2′-azino-bis-3- ethylbenzothiazoline-6-sulfonic acid assay (1.451 and 1.343 mMTE/g DW, respectively). The major phenolic acids and some flavonoid aglycones and glycosides were analyzed by high-performance liquid chromatography. Luteolin (2,706.20 µg/g DW), hesperidin (2,641.46 µg/g DW), sinapic acid (1,296.78 µg/g DW) and ferulic acid (619.80 µg/g DW) were predominant in the H. rhodopensis 70% alcohol extract. PRACTICAL APPLICATIONS The research yielded novel information about Haberlea rhodopensis, a less-explored endemic plant. The aim of the present study was to determine the antioxidant capacity of this resurrection plant with a focus on phenolic antioxidants rather than enzymes. High-performance liquid chromatography analysis was performed to quantify the major phenolic acids and flavonoids. The antioxidant potential of the extracts obtained was estimated using different approved methods. The results suggested the possibility of practical application of H. rhodopensis leaf extracts because of the established free radical-scavenging activity.