This is very interesting research so kudos to you for finding it. I was confused by it too until I realized that the point of the paper was to contemplate the specific mechanism of action of the antiretroviral effects of hypericin and pseudohypericin (from St. John's Wort), which they had previously discovered and written about
in a prior article published a year earlier. I think the prior article is more useful to us as patients:
Therapeutic agents with dramatic antiretroviral activity and little toxicity at effective doses: aromatic polycyclic diones hypericin and pseudohypericin.
When reading complicated research articles like this, even if I have the full text article I usually read the introduction and then skip to the discussion section. I just skim any parts I don't understand due to jargon and focus on the ones I can understand.
Anyway they found these compounds highly effective against a retrovirus in vivo, though the caveats to keep in mind are that this was a mouse study and that the active components of SJW were refined and injected rather than orally administered. Still could be very promising and since this article is 20 years old I will look for newer research when I get a chance.