Antioxidant and Anti-Inflammatory Activities in Relation to the Flavonoids Composition of Pepper (Capsicum annuum L.)

Abstract

The chili pepper (Capsicum annuum L.) is a food source that is rich in flavonoids such as luteolin and apigenin. Flavonoids are known to have anti-inflammatory and antioxidant activities; however, studies on the flavonoids composition identified and the anti-inflammatory and antioxidant effects in pepper leaves (PL) and fruits (PF) are insufficient. In the present study, we investigated the antioxidant and anti-inflammatory effects in vitro, and the flavonoids contents of the PL and PF. Pepper extracts showed radical scavenging activities and ameliorated the lipopolysaccharide (LPS)-stimulated inflammatory response by decreasing nitric oxide production and interluekin-6 and tumor necrosis factor alpha levels in RAW 264.7 cells, with more effective activities noted for PL than for PF. Furthermore, PL extracts markedly inhibited the LPS-induced production of reactive oxygen species accumulation. The flavonoid profile and content of pepper were dependent on the part, with PL showing higher total flavonoids than PF. In particular, the content of luteolin glycosides in PL was twice that in PF. Thus, PL may be useful to prevent oxidative stress and inflammation-related diseases.

Keywords: luteolin; pepper fruit; pepper leaf; reactive oxygen species.

Figure 1

Inhibition of nitric oxide (NO) production by the extracts of pepper leaves (PL) and pepper fruits (PF) in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. RAW 264.7 cells were treated with 100 (L), 200 (M), and 500 (H) µg/mL PL and PF extracts in the presence of 100 ng/mL LPS for 18 h. Statistical significance is based on the difference compared with CON(+) (* p < 0.05, *** p < 0.001).

Figure 2

Suppression of (A) interleukin (IL)-6 and (B) tumor necrosis factor (TNF)-α secretion by the extracts of pepper leaves (PL) and pepper fruits (PF) in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. RAW 264.7 cells were treated with 100 (L), 200 (M), and 500 (H) µg/mL PL and PF extracts in the presence of 100 ng/mL LPS for 18 h. Statistical significance is based on the difference compared with CON(+) (** p < 0.01, *** p < 0.001).

Figure 3

Pepper leaves (PL) extracts suppress reactive oxygen species (ROS) generation in lipopolysaccharide (LPS)-stimulated macrophages. (A) RAW 264.7 cells were treated with luteolin (LUT) 10 µM and various concentrations of PL extracts (100 and 500 µg/mL). Dichloro-dihydro-fluorescein diacetate (DCFH2-DA) was added to the culture medium at a final concentration of 50 µM. DCF fluorescence was imaged under a fluorescence microscope (100× magnification). (B) ROS inhibition rate, compared to control (+), was quantified by measuring the DCF fluorescence intensity. Statistical significance is based on the difference compared with CON (+) (*** p < 0.001).