# Quercetin Enhances Gastric Nitric Oxide Formation and Potentiates the Antihypertensive Effects of Oral Nitrite Administration

## TL;DR

Quercetin boosts the stomach's ability to convert nitrite into nitric oxide, enhancing its blood pressure-lowering effects in hypertensive rats.

## Contribution

Quercetin enhances gastric nitric oxide formation and potentiates antihypertensive effects of low-dose nitrite.

## Key findings

- Quercetin converts a nonantihypertensive nitrite dose into an effective one by increasing gastric NO formation.
- Quercetin does not increase systemic or vascular nitrite, nitrate, or protein nitrosation.
- The combination of quercetin and nitrite may offer a safe and effective antihypertensive strategy.

## Abstract

Oral nitrite supplementation enhances nitric oxide (NO) bioavailability and lowers blood pressure. Quercetin may facilitate the reduction of nitrite to NO. However, the combined effects of nitrite and Quercetin on gastric NO formation and blood pressure have not been explored. We investigated whether oral treatment with Quercetin enhances the gastric conversion of nitrite to NO (in vitro and in vivo) and exerts antioxidant and antihypertensive effects. Spontaneously hypertensive rats (SHR) were divided into six groups (n = 6/group): three groups treated with Quercetin 10 mg/kg followed 15 min later by water, nitrite 1 mg/kg (nonantihypertensive) or 15 mg/kg (antihypertensive) by gavage, and three similar control groups treated with vehicle, followed by the same nitrite treatments. Blood pressure, gastric NO, plasma nitrite, nitrate, nitrosylated species (RxNO) and aortic S‐nitrosylated proteins were measured. Oxidative stress was also assessed. Quercetin treatment converted a nonantihypertensive dose of nitrite into an effective antihypertensive intervention in association with increased in vitro and in vivo gastric NO formation. However, Quercetin did not enhance nitrite‐induced increases in systemic or vascular nitrite, nitrate, RxNO concentrations nor vascular protein nitrosation. Our results show that Quercetin is a potent enhancer of gastric NO formation from nitrite and amplifies its antihypertensive effects. This combination of drugs may represent a safe and effective therapeutic strategy.

Nitric oxide (NO) is important to control blood pressure. Sodium nitrite can increase NO levels, and quercetin, a common dietary antioxidant, may enhance this effect. In this study, hypertensive rats received nitrite with or without quercetin. Quercetin boosted the stomach’s ability to convert nitrite into NO, turning a low, otherwise ineffective nitrite dose into one that lowered blood pressure. This effect was linked to increased NO formation in the stomach, but not in the blood or vessels. Taken together, quercetin and nitrite may safely improve blood pressure control.