Melanin is an antioxidant but melatonin is a better one.
And dark-complexioned people have fewer ACE2 receptors on the lungs and other organs to host the virions.
There are many antioxidants. I don’t know how one decides one is better than the other, but I’d say in terms of simple side effects, melatonin is not exactly the most effective way to combat oxidative stress in the body. It may be a tool that can be used sparingly, but the hormonal disruptions it can cause (at least for me) are too great at anything but a tiny dose for me to put up with.
I’d stick with SOD, glutathione, garlic, vitamin C, and astragalus for a good base of combating oxidative stress and warding off bugs.