Didn't hear about quinin in grapefruits, however it have some similar substance - naringin, that reacts with our taste receptors in similar way. It also have two connected benzene rings (naphtalene ring), but have no nitrogen in ring. It is also fluorescent. I don't know what exact part of HCQ do the job, so it is hard to tell is it similar relative to the topic or not.

In any case grapefruit have huge amount of vitamin C which is definitely useful to fight the flu/cold.

Meanwhile, sunflower seeds have 5mg/100g Zn.

Don't hear about quinin in grapefruits, however it have some similar substance - naringin, that reacts with our taste receptors in similar way. It also have two connected benzene rings (naphtalene ring), but have no nitrogen in ring. It is also fluorescent. I don't know what exact part of HCQ do the job, so it is hard to tell is it similar relative to the topic or not.

In any case grapefruit have huge amount of vitamin C which is definitely useful to fight the flu/cold.

Meanwhile, sunflower seeds have 5mg/100g Zn.