Quercetin, a natural anti-oxidant, anti-inflammatory and anti-blood clot compound contained in abundance in various fruits and vegetables, is a zinc ionophore. The major benefit of taking quercetin with zinc is that the quercetin will push the zinc into the center of the cell where the zinc can stop the virus from reproducing.
Quercetin has been shown to inhibit proinflammatory cytokine production as well as inflammation due to its antioxidant properties, amongst others. By inhibiting destructive inflammation and potentially the entire cascade, quercetin may prevent severe damage to the respiratory system amongst other organs (source).
NAC inhibits cellular entry and replication of some respiratory viruses, assists in clearing thickened mucous from the airways, suppresses inflammatory signalling, and may help mitigate viral infection-induced cytokine storm (Ref). NAC may also protect against coagulation problems associated with COVID-19, as it has both anticoagulant (source) and thrombolytic effects (source), meaning it may both prevent clots and break up clots that have already formed.
Why are some retailers and Amazon no longer selling NAC? The US FDA made it clear in 2020 that it considers NAC to be a drug and not a dietary supplement, so, for legal reasons, some companies have stopped selling it in United States.
The history of bromelain is heavily linked to pineapple because it is the only known major source for this group of enzymes. Its first primary source was the pineapple fruit, before it was discovered that the mature pineapple stem had much more concentrated bromelain content.
Through the years after its discovery, the production of bromelain has broadened. Its commercialization has led manufacturers into developing faster extraction techniques for large-scale production and purification. Today, bromelain supplements are used for numerous health approaches.
These uses have been observed to be dependent on the time when it is taken. For example, if taken after a meal, bromelain may help promote better digestion and absorption, but when taken on an empty stomach, it can help alleviate inflammation (Daily Mail).
Quercetin works best when taken with vitamin C and Bromelain, as vitamin C helps activate it and bromelain helps with the absorption.
Quercetin is also part of the FLCCC I-MASK+ protocol and Zelenko protocol for COVID-19.