The flavonoid naringin is the main source of the undesirable bitter taste in some citrus juices. In commercial debittering processes, the naringin is adsorbed on non-ionic polymeric resins. Organo-clays (OCs), which have been used as sorbents for organic pollutants, could also have affinity for the naringin molecule, and thus potentially could serve as a debittering agent. The objective of the present study was to characterize the sorption capacity of a prepared OC to evaluate its ability to remove naringin from aqueous solutions, investigating the effect of adsorbent dose, initial concentration of naringin, temperature, contact time, and pH. The OC was prepared by the intercalation of cationic surfactant hexadecyltrimethylammonium bromide in a Mexican bentonite. The host clay and the OC were characterized by X-ray diffraction, Fourier-transform infrared, and nitrogen gas adsorption. The OC showed a surface area of 9.3 m2 g-1, 11.35 nm average pore diameter, and a basal spacing, d001, of 2.01 nm. The adsorbent removed naringin at the rate of 60-72% at 25°C and pH 3. The sorption capacity increased with pH and temperature. Experimental data were well fitted by both Langmuir and Freundlich adsorption models. Most of the sorption took place during the first 10 min and the equilibrium time was reached within 720 min. The rate of sorption was adjusted to pseudo second-order kinetics.

Drynaria fortunei (Kunze) J. Sm. (DF), a Chinese herb commonly used for the treatment of bone fracture, was previously shown to exert anabolic effects on bone. However, its active ingredients as well as the mechanisms of action are far from clear. The present study aimed to characterise the bone anabolic effects of DF flavonoid fraction (DFTF) in ovariectomised (OVX) mice and to determine if DFTF and its isolated compounds exert oestrogen-like effects in rat osteoblast-like UMR-106 cells. Young OVX C57/BL6J mice were treated orally with DFTF (0·087, 0·173 or 0·346 mg/g per d), 17β-oestradiol (2 μg/g per d) or its vehicle for 6 weeks. Serum and urine samples were collected for biochemical marker analysis. Bones were collected for computed tomography analysis. UMR-106 cells were treated with DFTF and isolated compounds naringin, (2S)-5,7,3′,5′-tetrahydroxy-flavonone 7-O-neohesperidoside (compound 1) and 5,7-dihydroxychromone 7-O-neohesperidoside (compound 2). DFTF exerted dose-dependent effects in improving bone mineral densities as well as bone strength at the femur, tibia and lumbar spine L1 in OVX mice. DFTF and the three isolated compounds stimulated osteoblastic cell proliferation and alkaline phosphatase activities in a dose-dependent manner. In addition, they stimulated the ratio of osteoprotegrin and receptor-activator NF-κB ligand mRNA expression, suggesting their involvement in inhibiting osteoclastogenesis. These stimulatory effects on osteoblastic functions were abolished in the presence of oestrogen receptor (ER) antagonist, ICI 182780. The present results suggested that DFTF is effective in protecting against OVX-induced bone loss in mice, and its actions in regulating osteoblastic activities appear to be mediated by ER.

Twenty Assaf lambs fed barley straw plus a concentrate alone (CONTROL group) or enriched with naringin (1.5 g/kg DM, NARINGIN group) were used to assess the effect of this polyphenolic compound on meat quality attributes. Serum samples were collected for 7 weeks, then the animals were slaughtered and the livers and longissimus thoracis et lumborum muscles extracted for analysis. Triacylglycerol levels in the serum samples tended to show (P = 0.087) lower average values for the NARINGIN group when compared with the CONTROL, but no differences were observed when the meat was analysed for the intramuscular fat content. Lower thiobarbituric acid-reactive substances procedure (TBARS) values (P < 0.001) in the liver of the NARINGIN group were detected, probably as a consequence of naringenin accumulation in this organ. No significant differences were observed in the meat samples concerning TBARS or colour evolution during refrigerated storage, as not enough naringenin would have reached the muscle. Independent of naringin administration, the low levels of the most atherogenic oxysterols must be highlighted as the most important quality score in the lamb meat samples studied.

Naringin, a bioflavonoid isolated from grapefruit, is well known to possess lipid-lowering and insulin-like properties. Therefore, we assessed whether naringin treatment ameliorates insulin resistance (IR), β-cell dysfunction, hepatic steatosis and kidney damage in high-fat diet (HFD)–streptozotocin (STZ)-induced type 2 diabetic rats. Wistar albino male rats were fed a HFD (55 % energy from fat and 2 % cholesterol) to develop IR and on the 10th day injected with a low dose of streptozotocin (40 mg/kg, intraperitoneal (ip)) to induce type 2 diabetes. After confirmation of hyperglycaemia (>13·89 mmol/l) on the 14th day, different doses of naringin (25, 50 and 100 mg/kg per d) and rosiglitazone (5 mg/kg per d) were administered orally for the next 28 d while being maintained on the HFD. Naringin significantly decreased IR, hyperinsulinaemia, hyperglycaemia, dyslipidaemia, TNF-α, IL-6, C-reactive protein and concomitantly increased adiponectin and β-cell function in a dose-dependent manner. Increased thiobarbituric acid-reactive substances and decreased antioxidant enzyme activities in the serum and tissues of diabetic rats were also normalised. Moreover, naringin robustly increased PPARγ expression in liver and kidney; phosphorylated tyrosine insulin receptor substrate 1 in liver; and stress proteins heat shock protein (HSP)-27 and HSP-72 in pancreas, liver and kidney. In contrast, NF-κB expression in these tissues along with sterol regulatory element binding protein-1c and liver X receptor- expressions in liver were significantly diminished. In addition, microscopic observations validated that naringin effectively rescues β-cells, hepatocytes and kidney from HFD-STZ-mediated oxidative damage and pathological alterations. Thus, this seminal study provides cogent evidence that naringin ameliorates IR, dyslipidaemia, β-cell dysfunction, hepatic steatosis and kidney damage in type 2 diabetic rats by partly regulating oxidative stress, inflammation and dysregulated adipocytokines production through up-regulation of PPARγ, HSP-27 and HSP-72.