Which Acid is Found in Saliva?

The reference indicates that 4-hydroxyphenylacetic acid (HPA) is found in human saliva.

Acids in Saliva: 4-Hydroxyphenylacetic Acid (HPA) and Related Information

Human saliva is a complex fluid containing various components, including acids. According to the provided reference, one of the notable acids found in saliva is 4-hydroxyphenylacetic acid (HPA). The reference also highlights the presence of nitrite which, under acidic conditions, reacts with HPA to form 4-hydroxy-3-nitrophenylacetic acid (NO₂HPA).

Here’s a detailed breakdown:

4-Hydroxyphenylacetic Acid (HPA)

• Presence: HPA is present in saliva at concentrations ranging from 2 to 10 microM.
• Significance: While the provided reference focuses on its reaction with nitrite, HPA's presence in saliva indicates its role in the biological processes within the oral cavity.
• Reaction: HPA is reactive. When mixed with sodium nitrite at a low pH (pH 1.0), it is nitrated to 4-hydroxy-3-nitrophenylacetic acid (NO₂HPA). This nitration can also occur within saliva under acidic conditions.

Nitrite in Saliva

• Presence: Nitrite is also a significant component of saliva, found in concentrations between 60 and 300 microM.
• Role in Reactions: As the reference indicates, nitrites are crucial for the formation of NO₂HPA from HPA under acidic conditions.

Summary Table

Compound	Concentration in Saliva
4-hydroxyphenylacetic acid (HPA)	2-10 microM
Nitrite	60-300 microM

Understanding the presence and interactions of acids like HPA in saliva is important for comprehending the biochemical processes that occur in the mouth. For instance, the acidic conditions created during certain processes can lead to the formation of NO₂HPA.

Therefore, the acid found in saliva, according to the reference, is 4-hydroxyphenylacetic acid (HPA).