Amazon did something similar with NAC [N-Acetyl Cysteine & N-Acetyl L-Cysteine] during the pandemic, after it was discovered that NAC helped with Covid symptoms.
“NMN is a naturally occurring molecule”
https://www.healthline.com/health/nmn-nicotinamide-mononucleotide-benefits-side-effects-and-dosage
This supplement cannot be patented. It was already sold as a commodity so you can’t walk it back and patent it.
You can patent it for a particular purpose, but that makes for very weak protection. Probably not worth patent filing fees, much less patent attorneys’ fees.
You can get it at the Vitaminshoppe.