Abstract
Evaluation of native plant resources and their efficient use is one of the current trends in phytochemistry. The main aim of the present study was to investigate the biological activities of different Rhododendron luteum Sweet leaf extracts obtained with the use of accelerated solvent extraction using different solvents and extraction temperatures. All extracts were subjected to bioactivity assays, which revealed considerable anti-lipoxygenase (23.07–90.13% lipoxygenase inhibition) and antiradical potential. All samples exhibited high 2,2-diphenyl-1-picrylhydrazyl (DPPH•) (234.18–621.90 mg Trolox equivalents (TE)/g) and 2,2′-azino-bis-3(ethylbenzthiazoline-6-sulphonic acid) (ABTS•+) (88.79–349.41 mg TE/g) scavenging activity, high antioxidant potential in the Oxygen Radical Absorbance Capacity (ORAC) assay (495.77–1011.59 mg TE/g), and moderate ion chelating (Fe2+) capacity. The chemical profile of each sample was determined using liquid chromatography/electrospray ionization triple quadrupole mass spectrometry (LC-ESI-MS/MS) and spectrophotometric procedures. Twenty-three compounds representing seven polyphenol subclasses were detected and quantified, including some phenolic acids and flavonoids that had not been previously reported for this plant material. It was shown that 5-O-caffeoylquinic acid, protocatechuic acid, catechin, quercetin and its glycosides (hyperoside, isoquercetin, quercitrin), and pentacyclic triterpenes were the dominant secondary metabolites in R. luteum leaves. The antioxidant activity was found to be strongly related to different polyphenol groups and total triterpene content, while the anti-lipoxygenase potential was highly dependent on catechin.
Highlights
Chronic inflammation and oxidative stress contribute to the emergence and development of many diseases, for example, cancer, cognitive dysfunctions, rheumatoid arthritis, or heart diseases
It was shown that 5-O-caffeoylquinic acid, protocatechuic acid, catechin, quercetin and its glycosides, and pentacyclic triterpenes were the dominant secondary metabolites in R. luteum leaves
Since antioxidant and anti-inflammatory activity are attributed to the presence of polyphenols [1,4,29] and triterpenes [7,8,9,10], total phenolic (TPC), total flavonoid (TFC), and total triterpene content (TTC) were determined in all the examined extracts
Summary
Chronic inflammation and oxidative stress contribute to the emergence and development of many diseases, for example, cancer, cognitive dysfunctions, rheumatoid arthritis, or heart diseases. Plant secondary metabolites may exhibit direct and indirect anti-inflammatory and antioxidant potential, without showing severe adverse effects [1,2]. Many popular anti-inflammatory drugs may cause nagging or painful side effects, e.g., damage to gastric mucosa, reduced production of gastric acid, diarrhea, or nausea [3]. Searching for new natural and safe agents seems to be a promising alternative. Many studies suggest that polyphenols, including flavonoids, possess significant antioxidant and anti-inflammatory potential. They can present many mechanisms of action, such as inhibition
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