The anti-inflammatory activity of natural allophane

• Natural allophane acts as anti-inflammatory.
• At 4 h, applying 1 mg ear− 1 allophane, MPO content inhibition values surpassed 60%.
• Edema was mediated by the migration of neutrophils at t = 4 h, but not at t = 24 h.
• Highly-active allophane contained octahedral Fe3 + (S = 1/2) and Ni (+ 1, + 3, or + 2).

This paper presents evidence of the novel anti-inflammatory properties of natural allophane collected from New Zealand, Japan, and Ecuador. Allophanes were assessed by (i) the mouse-ear edema method using 12-O-tetradecanoylphorbol-13-acetate (TPA) as inflammatory agent; and (ii) the myeloperoxidase (MPO) enzymatic-activity method. After 4 h, applying 1 mg ear− 1 allophane conveyed edema inhibition (EI; p ≤ 0.01) in up to 39%, while MPO content inhibition (CI) values surpassed 60%. Pearson's correlation analysis between EI and MPO data showed that edema was mediated by the migration of neutrophils at t = 4 h (p < 0.05), but not at t = 24 h. The lack of variation in cellular migration with time was explained because of a reaction of zero-order kinetics. EPR spectra for allophanes showing higher anti-inflammatory activity denoted a broad signal centered at g = 2, and an intense spin–spin interaction, typical of a low-spin, octahedral Fe3 + environment (S = 1/2); and overlapping signals typical for Ni, with octahedral coordination, explained either by oxidation states + 1 (Ni1 +), + 3 (Ni3 +), or bulk Ni2 + ions.

After 4 h, naturally-occurring allophanes (Allo-1, Allo-2, Allo-3, Allo-E), primary components of respirable volcanic ash (< 4 μm aerodynamic diameter), present novel anti-inflammatory properties, comparable to those by naturally-occurring halloysite (PA, CLA-1) and commercial indomethacin.Figure optionsDownload as PowerPoint slide