Profile of nitric oxide (NO) metabolites (nitrate, nitrite and N-nitroso groups) in honeys of different botanical origin: nitrate accumulation as index of origin, quality and of therapeutic opportunities

Besides dermoprotective activity, honey also has a strong gastroprotective effect, from salivary reduction of nitrate (NO3-) to nitrite (NO2-) and intragastric formation of nitric oxide (NO), this lastly involved in the preservation of the gastric mucosa capillaries and in boosting mucous production. Aim of this work is to profile the distribution of NO metabolites (NO3-, NO2- and total N-nitroso-groups, N-NO) in a set of honeys (n=54) of different botanical origins, using a chemiluminescence based technique (NO-analyzer, NOA). All the honeys contained appreciable amounts of NO3- (from 1.63±0.04 to 482.98±5.34mg/kg), the highest in honeydew honeys (10-40 times than in nectar honeys). Low levels of NO2- were found in all samples (0.01±0.00 to 0.56±0.01mg/kg). N-NO groups, at trace levels in some nectar honeys, were higher in honeydew samples (from 0.01±0.00 to 0.29±0.01mg/kg). Total phenol content (TP) and total protein (TProt) were comparable to those in literature. Multivariate analysis indicated that N-NO groups were significantly associated with NO2- and TP thus to suggest an in situ environmental nitrosation of specific nitrosable substrates (lysine, proline) favored by high reducing conditions. The bee-smoking process can be an alternative or complementary explanation for N-NO contamination. Hence NO3- rich honeys intake may exert beneficial effects against NSAIDs-induced gastric injury. Finally NO3- is a potential reliable marker of a honey's origin and quality.