Biophysical and Spectrophotometric Evaluation of Nitrite in Human Saliva

Abstract

Salivary glands and oral bacteria play an essential role in converting dietary nitrate to nitrite and then to nitric oxide, which is a multifunctional signaling molecule involved in vascular and metabolic functions. In addition to the endogenous arginine pathway, dietary nitrate represents the main external source of nitric oxide through a sequential conversion from nitrate to nitrite to nitric oxide. Salivary nitrite normally remains below 7 milligrams per liter. Elevated levels may result from high intake of nitrate rich vegetables, poor oral health such as dental caries or periodontal disease, or systemic conditions including type 2 diabetes mellitus and kidney dysfunction. This cross sectional study aimed to quantitatively determine salivary nitrite concentrations in young adult students using a spectrophotometric method, compare the results with normal values, and discuss their physiological and pathophysiological significance. Fifteen saliva samples were collected from healthy volunteers aged 20–24 years after 8–10 hours of fasting; samples were stabilized with sodium hydroxide, deproteinized with zinc sulfate, centrifuged, and analyzed at 507 nm using a DR 900 spectrophotometer according to HACH method 8507. The results showed a mean nitrite concentration of 10.9 mg/L (range 6.7–24.3 mg/L). Only 26.7% of samples were within the normal limit (≤7 mg/L), while 73.3% exceeded it, with two samples showing markedly elevated levels above 20 mg/L. The most likely explanations for these elevations are recent consumption of green leafy vegetables (physiological) and undiagnosed oral health problems such as dental caries or gingivitis (pathophysiological), although early systemic conditions like diabetes or kidney disease cannot be completely excluded. The study concludes that salivary nitrite is a promising non invasive biomarker, but its interpretation requires careful control of dietary, oral hygiene, and circadian factors; larger controlled studies with standardized protocols are needed to establish population specific reference ranges and validate its clinical utility.