The Leech Woman (1960)

When a very old African woman offers an ambitious endocrinologist the secret of eternal youth, he decides to take his estranged and no-longer-young-and-beautiful wife along with him on the safari. But then she finds out the true reason for their sudden reconciliation is so that she can serve as his guinea pig. Hell hath no fury like a woman scorned, especially one with a stolen pineal gland tapper. But once you try Nipe, there's no going back.