Suppression of cytokine production by newly isolated flavonoids from pepper

New flavonoid glycoside, kaempferol 3-O-alpha-[(6-P-coumaroyl galactopyranosyl-O-beta-(-> 4)-O-alpha-rhamnopyranosyl(1 -> 4)]-O-alpha-rhamnopyranoside 1, in addition to five known flavonoid glycosides (2-6) kaempferol 3-O[alpha-rhamnopyranosyl-(1 -> 4)-O-alpha-rhamnopyranosyl-(1 -> 6)-O]-beta-galactopyranoside (kaempferol 3-O-beta-isorhamninoside) 2, quercetin 3-O-[(2,3,4-triacetyl-alpha-rhamnopyranosyl)-(1 -> 6)-beta-galactopyranoside 3, quercetin 3-O-[(2,4-diacetyl-alpha-rhamnopyranosyl)-(1 -> 6)]-3,4-diacetyl-beta-galactopyranoside 4, quercetin 3-O-[(2,4-diacetyl-alpha-rhamnopyranosyl)-(1 -> 6)]-2,4-diacetyl-beta-galactopyranoside 5, quercetin 3-O-[(2,3,4-triacetyl-alpha-rhamnopyranosyl)-(1 -> 6)-3-acetyl-beta-galactopyranoside 6 were isolated from bell pepper (Capsicum annum L.) fruits and tested for both anti-inflammatory activity through cytokine production (TNF-alpha and IL-1 beta) and antioxidant activity through scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. Compounds 1-3 significantly suppressed production of TNF-alpha / IL-1 beta in cultured THP-1 cells previously co-stimulated by LPS in a dosedependent manner (10.2/49.1, 28.1/55.7, and 35.2/57.5 mu M respectively) whereas compounds 4-6 have relatively weaker inhibitory activity. (45.3/73.5, 48.2/65.6, and 42.2/67.4 mu M respectively). All compounds 1-6 showed no cytotoxic activity against the growth of THP-1where the percentage of cell viability was (127.4, 108.5, 105.4, 103.9, 103.4, and 104.2 mu M respectively). All isolated compounds exhibited higher radical scavenging activity than ascorbic acid in (DPPH) assay. These results indicated that bell pepper fruits could be an effective candidate for ameliorating inflammatory-associated complications.

Automated summary

A new flavonoid glycoside, along with five known compounds, were isolated from bell pepper fruits and tested for anti-inflammatory and antioxidant activities. The study showed that compounds 1-3 had significant inhibitory effects on cytokine production, while compounds 4-6 exhibited weaker activity. All compounds showed no cytotoxicity and higher radical scavenging activity compared to ascorbic acid. Bell pepper fruits could be a potential candidate for treating inflammatory-associated complications.