Protective Effects of Wild Sulla coronaria (Fabaceae) Flowers Phytocomplex in Human Dermal Fibroblasts Stimulated with Interleukin-1β

Abstract

Sulla coronaria is indigenous to the Mediterranean region. It is grown as fodder in southern Italy because it contains various secondary metabolites with beneficial activities on animals. Recently, its potential use in cosmeceutical treatments for skin problems was reported. In this scenario, to contribute to a possible cosmeceutical application, we characterized the phytochemical profile of Sulla coronaria flowers' hydroalcoholic extract by HPLC-DAD, Folin-Ciocalteu, Aluminum Chloride methods, DPPH assay, and, for the first time, we evaluated the antioxidant and anti-inflammatory activities on dermal fibroblasts. The phytochemical analysis confirmed the significant content of phenolic compounds (TPC 69.8 ± 0.6 mg GAE/g extract, TFC 15.07 mg CE/g extract) and the remarkable presence of rutin, quercetin, and isorhamnetin derivatives that give to the phytocomplex a good antioxidant activity as highlighted by the DPPH assay (IC₅₀ of 8.04 ± 0.5 µg/mL). Through the reduction in NO• and ROS levels in human dermal fibroblasts, the biological tests demonstrated both the safety of the extract and its ability to counteract the inflammatory state generated by Interleukin-1β exposure. Our findings indicate that the antioxidant activities of the phytocomplex are strictly related to the anti-inflammatory action of the Sulla coronaria flowers extract, confirming that this plant could be a valuable source of bioactive molecules for cosmeceutical and nutraceutical applications.

Keywords: Hedysarum coronarium; NO•; ROS; Sicilian vascular flora; flavonols; nitrites/nitrates; polyphenols; quercetin.

Figure 1

Blooming of wild Sulla coronaria plant at the collection site (Corleone, Palermo, Italy).

Figure 2

HPLC-DAD phytochemical fingerprint of Sulla coronaria flower hydroalcoholic extract. Column: Ascentis Express C18, 15 cm × 4.6 mm, 2.7 µm d.p. The numbers indicating peaks refer to the identified compounds reported in Table 2.

Figure 3

Aglycone chemical structures of the identified compounds in Sulla coronaria flower hydroalcoholic extract.

Figure 4

Cytotoxic effect of Sulla coronaria flower hydroalcoholic extract on HDF cells. An MTT test was performed on HDFs treated with different concentrations of extract (from 10 to 1000 µg/mL) for 24 h. Data are represented as the means ± S.D. of three independent experiments. Confidence intervals calculated by one-way ANOVA test: * Significant vs. untreated control cells.

Figure 5

ROS production in HDF untreated cells (Ctr), treated for 12 h with IL-1β (10 ng/mL), and pre-treated for 24 h with the extract (50–100–200 μg/mL). Results are expressed as the percentage of the intensity of fluorescence (I.F.) vs Ctr. Values are the mean ± S.D. of three experiments in triplicate. Confidence intervals calculated by one-way ANOVA test: * Significant vs. untreated control cells: p < 0.05; # Significant vs. IL-1β-Stimulated cells: p < 0.05.

Figure 6

Effect of Sulla coronaria flower extract on NO• production in HDF cells. A Griess assay was performed on the supernatant of IL-1β-stimulated cells non-treated and treated with the extract (50, 100, and 200 µg/mL) for 24 h. Data are represented as the means ± SD of three independent experiments. Confidence intervals calculated by one-way ANOVA test: * Significant vs. untreated control cells: p < 0.05; # Significant vs. IL-1β-Stimulated cells: p < 0.05.