Mangosteen, improve joint flexibility and immune system function.
Mayo Clinic reports research on drinking mangosteen juice to soothe arthritis pain and swelling, encouraging, though not definitive.

FDA has not approved mangosteen as safe or effective.

It has however approved washing powders that are carcinogenic to humans, and have just been outed - oops.

It has also approved EU mRNA genetic cell therapy vaxxes which probably will make your heart explode. But keep yer paws off that mangosteen juice people.