No abstract

Tamarillo (Solanum betaceum) is a tropical exotic fruit whose polysaccharides were extracted from the ripe pulp. After various purification steps, homogeneous fractions (designated PTW, STK-1000R and PF) were analyzed by sugar composition, HPSEC, methylation and NMR spectroscopy analysis. The results showed that the fraction PTW consisted of a linear arabinan with (1→5)-linked α-l-arabinofuranosyl units. Fractions designated as STK-1000R and PF contained galactoarabinoglucuronoxylans, with (1→4)-linked β-d-Xylp residues in the backbone, carrying branches exclusively at O-2. The polysaccharide in STK-1000R is less branched than that in the PF fraction (∼20.0% and 36.5%, respectively), with side-chains formed by (1→5)-linked α-l-Araf residues and (1→4)-linked α-d-GlcpA residues and with non-reducing end units formed by α-l-Araf, β-Arap, β-d-Galp, α-d-GlcpA and 4-O-Me-α-d-GlcpA. Intraperitoneal administration of the STK-1000R fraction in mice significantly reduced the number of abdominal constrictions induced by 0.6% acetic acid and the inflammatory phase of nociception induced by 2.5% formalin, indicating that that fraction has an antinociceptive effect on inflammatory pain models.

Naringenin (NG) is a flavanone abundant in grapefruit and other citrus fruits that presents several pharmacological effects, such as antioxidant, antiinflammatory, analgesic, among others. We investigated the antinociception of systemic administration of naringenin (NG) and some of the mechanisms of action underlying its effect. Intraperitoneal administration of NG (10 mg/kg) inhibited the mechanical allodynia induced by partial sciatic nerve ligation (PSNL) and carrageenan in 65 ± 4 and 43 ± 9% (2 h), respectively. NG also reduced the writhes number (30 mg/kg: 90 ± 9%) and the nociceptive response of formalin (100 mg/kg: 75 ± 12%, inflammatory phase), bradykinin (30 mg/kg: 79 ± 6%) and prostaglandin E 2 (100 mg/kg: 98 ± 1%). Besides, NG reduced the glutamate-induced nociception with ID50 value of 66 mg/kg, effect that was reversed by naloxone. NG, at antinociceptive doses, did not affect the locomotor activity. Our findings demonstrated that systemic NG exerts anti-allodynic activity in neuropathic pain model and antinociceptive effect in several chemical and inflammatory models of nociception, with participation of glutamatergic and opioid system.