Comparative studies on analytical, antioxidant, and antimicrobial activities of a series of vegetal extracts prepared from eight plant species growing in Romania

Abstract

Given the large applicability in both pharmaceutical and cosmetic field, this work was aimed at analytical (high-performance thin-layer chromatography [HPTLC] method), antioxidant (2,2-diphenyl- 1-picrylhydrazyl [DPPH] method), and antimicrobial (diffusion method on Staphylococcus aureus ATCC 6538, Escherichia coli ATCC 8739, and Candida albicans ATCC 10231) studies on a series of whole vegetal extracts and corresponding aqueous, ethyl acetate and chloroform fractions (selective extracts) prepared from eight plant species growing in Romania. Briefly, it was revealed moderate to certain activity against S. aureus ATCC 6538 and E. coli ATCC 8739 in the case of greater burdock leaves (Arctium lappa), beech leaves (Fagus sylvatica) and great willowherb aerial part (Epilobium hirsutum) whole extracts. Purple loosestrife aerial part (Lythrum salicaria) and sea-buckthorn leaves (Hippophae rhamnoides) whole extracts showed only weak activity against these bacteria, while tarragon aerial part (Artemisia dracunculoides), chokeberries leaves (Aronia melanocarpa) and quince fruit (Cydonia oblonga) whole extracts have not shown activity. Subsequently studies on the selective extracts have revealed that combinations of glycosides of the same aglycones lead to very different antimicrobial properties indicating synergistic effects between polyphenols (demonstrated in the case of Fagus sylvatica extracts) or the contribution of other phytocompounds to the final effect (demonstrated in the case of Arctium lappa extracts) and, secondly, that the glycosyl chain in which they occur may also contribute to the final antimicrobial effect (demonstrated by the fact that the most active vegetal extracts emphasized the dominance of flavonoid monoglycosides). Moreover, inhibitory antimicrobial effects were revealed (Arctium lappa extracts). Finally, none of the studied extracts acted against C. albicans ATCC 10231. Concerning antioxidant activity, DPPH tests indicated high potency of all tested extracts (IC50 measuring from 2.66 to 4.80). Further studies on the most active vegetal extracts which aim to reveal MICs values and potential inhibitory or activatory effects in combination with chemical antibiotics are ongoing.