Abstract
The present study aimed to assess the phenolic content of eight ethanolic propolis samples (P1–P8) harvested from different regions of Western Romania and their antioxidant activity. The mean value of total phenolic content was 214 ± 48 mg gallic acid equivalents (GAE)/g propolis. All extracts contained kaempferol (514.02 ± 114.80 μg/mL), quercetin (124.64 ± 95.86 μg/mL), rosmarinic acid (58.03 ± 20.08 μg/mL), and resveratrol (48.59 ± 59.52 μg/mL) assessed by LC-MS. The antioxidant activity was evaluated using 2 methods: (i) DPPH (2,2-diphenyl-1-picrylhydrazyl) assay using ascorbic acid as standard antioxidant and (ii) FOX (Ferrous iron xylenol orange OXidation) assay using catalase as hydrogen peroxide (H2O2) scavenger. The DPPH radical scavenging activity was determined for all samples applied in 6 concentrations (10, 5, 3, 1.5, 0.5 and 0.3 mg/mL). IC50 varied from 0.0700 to 0.9320 mg/mL (IC50 of ascorbic acid = 0.0757 mg/mL). The % of H2O2 inhibition in FOX assay was assessed for P1, P2, P3, P4 and P8 applied in 2 concentrations (5 and 0.5 mg/mL). A significant H2O2% inhibition was obtained for these samples for the lowest concentration. We firstly report the presence of resveratrol as bioactive compound in Western Romanian propolis. The principal component analysis revealed clustering of the propolis samples according to the polyphenolic profile similarity.
Highlights
AAbbssttrraacctt:: The present study aimed to assess the phenolic content of eight ethanolic propoolliiss sammpplleess ((PP11–-P8) hhaarrvveesstteeddfrforommdidffieffrernetnrtegreiogniosnosf WofeWsteersnteRronmRaonmiaaanniad athnedirtahnetiiroxaindtaionxtiadcatnivtitayc.tTivhietym
The antioxidant capacity of propolis strongly depends on its chemical composition, which in turn is influenced by the extraction 019; Published: datme ethods [10]
As regarding the principal component analysis (PCA) analysis of the 8 propolis samples, we report a clusterization as follows: P3, P5; P6, P8; P1, P7 and P2, P4
Summary
The percentage of DPPH free radical inhibition along with IC50 were determined. The IC50 varied from 0.0700 mg/mL for the P2 sample to 0.9945 mg/mL for P6 sample. Water extracts of Brazilian propolis were reported to exert antioxidant activity; the DPPH scavenging activity dose-dependently varied between 23.7% to 43.5% with ascorbic acid being used as positive control [42]. Of note, these studies used at least two techniques for the in vitro assessment of the antioxidant activity, one of them being the DPPH assay. We thought to use a second technique, FOX assay for the assessment of the % of H2O2 inhibition for the samples reported to have the highest and lowest DPPH scavenging activity, respectively While both concentrations act as H2O2 scavengers ( to catalase) a superior antioxidant effect was found for the low dose as compared to the high one. There is an unmet need for the standardization of the phenolic profile assessment in terms of both total content and individual specific compounds since the former and the latter might contribute to the antioxidant role [50]
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