Antioxidant Activity of Citrus Limonoids, Flavonoids, and Coumarins

Abstract

A variety of in vitro models such as beta-carotene-linoleic acid, 1,1-diphenyl-2-picryl hydrazyl (DPPH), superoxide, and hamster low-density lipoprotein (LDL) were used to measure the antioxidant activity of 11 citrus bioactive compounds. The compounds tested included two limonoids, limonin (Lim) and limonin 17-beta-D-glucopyranoside (LG); eight flavonoids, apigenin (Api), scutellarein (Scu), kaempferol (Kae), rutin trihydrate (Rut), neohesperidin (Neh), neoeriocitrin (Nee), naringenin (Ngn), and naringin(Ng); and a coumarin (bergapten). The above compounds were tested at concentration of 10 microM in all four methods. It was found that Lim, LG, and Ber inhibited <7%, whereas Scu, Kae, and Rut inhibited 51.3%, 47.0%, and 44.4%, respectively, using the beta-carotene-linoleate model system. Lim, LG, Rut, Scu, Nee, and Kae showed 0.5% 0.25%, 32.2%, 18.3%, 17.2%, and 12.2%, respectively, free radical scavenging activity using the DPPH method. In the superoxide model, Lim, LG, and Ber inhibited the production of superoxide radicals by 2.5-10%, while the flavonoids such as Rut, Scu, Nee, and Neh inhibited superoxide formation by 64.1%, 52.1%, 48.3%, and 37.7%, respectively. However, LG did not inhibit LDL oxidation in the hamster LDL model. But, Lim and Ber offered some protection against LDL oxidation, increasing lag time to 345 min (3-fold) and 160 min (33% increase), respectively, while both Rut and Nee increased lag time to 2800 min (23-fold). Scu and Kae increased lag time to 2140 min (18-fold) and 1879 min (15.7-fold), respectively. In general, it seems that flavonoids, which contain a chromanol ring system, had stronger antioxidant activity as compared to limonoids and bergapten, which lack the hydroxy groups. The present study confirmed that several structural features were linked to the strong antioxidant activity of flavonoids. This is the first report on the antioxidant activity of limonin, limonin glucoside, and neoeriocitrin.

Citrus medicaL. cv Diamante (Rutaceae) peel extract improves glycaemic status of Zucker diabetic fatty (ZDF) rats and protects against oxidative stress

“…Both mesocarp and endocarp of immature CD fruits were able to inhibit the discolouration of b-carotene with IC 50 values of 0.004 and 0.005 mg/ml, respectively at 60 min of incubation). As previously cited CD peel extract is a rich source of flavonoids that showed antioxidant activity by a different mechanism of action 35 . Both apigenin and hesperetin exhibited mild antioxidant potency.…”

Self-nanoemulsifying drug delivery system (SNEDDS) of the poorly water-soluble grapefruit flavonoid Naringenin: design, characterization,in vitroandin vivoevaluation

“…NRG has been reported to posses several effects on biological system such as antioxidant (Rice-Evans et al, 1996;Cao et al, 1997), anti-inflammatory (Manthey 2000), anticancer (Goldwasser, 2010), antifibrogenic (Lee et al, 2004) and antiatherogenic (Lee et al, 2001). The beneficial effects on human health are mainly due to their antioxidant activity and ability to chelate metals, to scavenge oxygen free-radical, to inhibit enzymes and to prevent oxidation of low-density lipoproteins (LDL) (Madsen et al, 2000;Yu et al, 2005). Even though NRG possesses a wide range of activities, clinical studies exploring different schedules of administration of this drug have been hampered by its extreme water insolubility and poor bioavailability.…”

Bergapten prevents lipopolysaccharide mediated osteoclast formation, bone resorption and osteoclast survival

“…Previous studies have shown that bergapten possesses anticarcinogenic, antiproliferative, vasorelaxation and antiallergic effects [5][6][7][8][9]. Moreover, it can enhance bone formation and possibly prevent osteoclastic bone resorption in vitro or in vivo [10,11], suggesting that bergapten may prevent or treat osteoporosis and other bone-destruction diseases.…”

“…1), a coumarin found in many medicinal plants, has been used for decades in combination with UV radiation in skin photochemotherapy. It has other biological functions, including anticancer [5,6], antioxidative [7,8] and anti-inflammatory [9] effects. Recently, Tang et al and Zhang et al reported that bergapten stimulates activity of osteoblastlike UMR106 cells and enhances bone morphogenetic protein-2 expression and bone formation via p38 and extracellular signal regulated kinase (ERK)-dependent pathway in osteoblasts of human osteosarcoma cell line (MG-63) and human fetal osteoblast (FOB) cell line [10,11].…”