Bioactivities of Flavonoids from Lopezia racemosa

Abstract

Lopezia racemosa Cav. (Onagraceae) has been used in Mexican traditional medicine to alleviate stomachache, biliary colic, urine retention, stomach cancer, and skin, dental, buccal, and urinary infections. The objective of this study was to determine the bioactivities of specific parts of the plant to scientifically confirm its traditional use. Aerial parts and flowers were macerated and subsequently extracted with hexane, chloroform, and methanol. This study was focused on the analysis of polar components, and thus the methanolic fractions were selected for further investigations. These fractions were evaluated for their antimicrobial activity using a panel of bacterial Gram-positive and -negative strains, as well as fungal strains, including filamentous fungi and yeasts. In addition, the cytotoxic activity of the extract was assessed by MTT using the human-derived monocytic THP-1 and the normal human fibroblast cell lines. Various fractions showed antimicrobial activity against various pathogens, although the most relevant were against Pseudomonas aeruginosa and Trichophyton mentagrophytes. No inhibition of yeasts was recorded. Only four fractions showed cytotoxic effects when the human-derived THP-1 and fibroblast cells were assessed. The four flavonoids isolated from the extract were luteolin, luteolin-6-C-hexoside, luteolin-8-C-hexoside, and hyperoside. The biological activities presented in this study validate some traditional uses of the plant.

Figure 1

UV absorption spectra of the methanolic fractions 216 – 229 in MeOH and shift observed after the addition of displacement reagents.

Figure 2

UV absorption spectra of the methanolic fractions 274 – 278 in MeOH and shift observed after the addition of displacement reagents.

Figure 3

UV absorption spectra of the methanolic fractions 279 – 293 in MeOH and shift observed after the addition of displacement reagents.

Figure 4

(a) FAB⁺ mass spectrum of 4, showing the [M+Na]⁺ (m/z 487), the [M+H]⁺ (m/z 465), [quercetin+H]⁺ (m/z 303), and the base peak [quercetin+Na-H₂O]⁺. (b) UV absorption spectra of 4 in MeOH and shift observed after the addition of displacement reagents.

Figure 5

Elution of the methanol extract from flowers separated on a Diaion HP-20.

Figure 6

FTIR spectrum of fractions 22 – 26 obtained from the methanolic extract of flowers separated on a Diaion HP-20 (top image) and FTIR spectrum of tannic acid (bottom image).

Figure 7

Cytotoxic activity of the methanolic fractions in (a) normal fibroblast and (b) THP-1 cells. PC = positive control. The dash line represents the untreated cells (negative control. Experiments were performed in triplicate. Data are presented as the mean ± SE. ∗ represents the significance level (P<0.05).