Phytochemicals, Antioxidant and Antimicrobial Potentials and LC-MS Analysis of Centaurea parviflora Desf. Extracts

Abstract

Centaurea parviflora (C. parviflora), belonging to the family Asteraceae, is an Algerian medicinal plant used in folk medicine to treat different diseases related to hyperglycemic and inflammatory disorders, as well as in food. The present study aimed to assess the total phenolic content, in vitro antioxidant and antimicrobial activity and phytochemical profile of the extracts of C. parviflora. The extraction of phenolic compounds from aerial parts was conducted using solvents of increasing polarity starting from methanol, resulting in crude extract (CE), to chloroform extract (CHE), ethyl acetate extract (EAE) and butanol extract (BUE). The total phenolic, flavonoid and flavonol contents of the extracts were determined using the Folin-Ciocalteu and AlCl₃ methods, respectively. The antioxidant activity was measured with seven methods: 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, galvinoxyl free-radical-scavenging test, 2,2'-Azino-Bis(3-Ethylbenzothiazoline-6-Sulfonic Acid) (ABTS) assay, cupric reducing antioxidant capacity (CUPRAC), reducing power, Fe⁺²-phenanthroline reduction assay and superoxide-scavenging test. The disc-diffusion method aimed at testing the sensitivity of bacterial strains toward our extracts. A qualitative analysis with thin-layer chromatography of the methanolic extract was performed. Moreover, HPLC-DAD-MS was used to establish the phytochemical profile of the BUE. The BUE was found to contain high amounts of total phenolics (175.27 ± 2.79 µg GAE/mg E), flavonoids (59.89 ± 0.91 µg QE/mg E) and flavonols (47.30 ± 0.51 µg RE/mg E). Using TLC, different components such as flavonoids and polyphenols were noted. The highest radical-scavenging ability was recorded for the BUE against DPPH (IC₅₀ = 59.38 ± 0.72 µg/mL), galvinoxyl (IC₅₀ = 36.25 ± 0.42 µg/mL), ABTS (IC₅₀ = 49.52 ± 1.54 µg/mL) and superoxide (IC₅₀ = 13.61 ± 0.38 µg/mL). The BUE had the best reducing power according to the CUPRAC (A_0.5 = 71.80 ± 1.22 μg/mL), phenanthroline test (A_0.5 = 20.29 ± 1.16 μg/mL) and FRAP (A_0.5 = 119.17 ± 0.29 μg/mL). The LC-MS analysis of BUE allowed us to identify eight compounds including six phenolic acids and two flavonoids: quinic acid, five chlorogenic acid derivatives, rutin and quercetin 3-o-glucoside. This preliminary investigation revealed that the extracts of C. parviflora have a good biopharmaceutical activity. The BUE possesses an interesting potential for pharmaceutical/nutraceutical applications.

Keywords: Centaurea parviflora; LC-MS; TLC; antimicrobial; antioxidant activity; flavonoids; polyphenols.

Figure 1

Photos of TLC results of methanolic extract of C. parviflora. (A) Toluene/Chloroform/Methanol; (B) Chloroform/Methanol; (C) Ethyl Acetate/Methanol/Water; (D) Methanol/Water; (E) Butanol/Acetic acid/Water.

Figure 2

Chromatogram of the positive ionization of the butanol extract of C. parviflora.

Figure 3

Chromatogram of the negative ionization of the butanol extract of C. parviflora.

Figure 4

Chromatogram of quinic acid (compound 1).

Figure 5

Mass spectrum of quinic acid (compound 1).

Figure 6

Chromatogram of chlorogenic acid (compounds 2, 3, 4 and 5).

Figure 7

Mass spectrum of chlorogenic acid (compounds 2, 3, 4 and 5).

Figure 8

Chromatogram of rutin (compound 6).

Figure 9

Mass spectrum of rutin (compound 6).

Figure 10

Chromatogram of quercetin 3-O-glucoside (compound 7).

Figure 11

Mass spectrum of quercetin 3-O-glucoside (compound 7).

Figure 12

Chromatogram of chlorogenic acid derivative (compound 8).

Figure 13

Mass spectrum of chlorogenic acid derivative (compound 8).

Figure 14

Photographs of the antibacterial activity results according to the agar disk-diffusion method of C. parviflora. 1. Standard (solvent), 2. 20 mg/mL, 3. 30 mg/mL.

Figure 14

Photographs of the antibacterial activity results according to the agar disk-diffusion method of C. parviflora. 1. Standard (solvent), 2. 20 mg/mL, 3. 30 mg/mL.