Which of the following is NOT a type of vitamin B3?

Vitamin B3, also known as niacin, encompasses two main forms: nicotinic acid and nicotinamide. Both forms play essential roles in the body, such as assisting in the conversion of food into energy and contributing to DNA repair. Nicotinamide riboside is also categorized as a type of vitamin B3 due to its role as a precursor to nicotinamide and its involvement in cellular energy metabolism.

Pyridoxal, on the other hand, is not a form of vitamin B3 but is actually related to vitamin B6. Vitamin B6 is crucial for various metabolic processes, including amino acid metabolism and neurotransmitter synthesis. Thus, it is distinct from the B3 vitamin family. In this context, recognizing pyridoxal as a vitamin B6 derivative clarifies why it does not belong to the vitamin B3 category.