METAL GEAR SOLID 3: Snake Eater - Master Collection Version

There are four types of medical items acquired from plants. The plants don't really have names, but they look like little shrubs on the ground that are a different color from the surrounding foliage. Go to the following locations and CQC at any odd-looking bush. They spawn in multiple locations, but here are guaranteed locations for them.

Cold Medicine (shows up as "C Med") - Dremuchij East
The rest can be found in Svytagornyj South:
Styptic
Disinfect
Splint

If you're having a hard time finding them, plant some TNT around the Svytagornyj South area and set them off. You'll the see the square boxes appear after the explosives.

Note: You must actually pick the plants up for them to count. And they must come from the plants, not as pre-existing items. If your health supplies are full, use an explosive at close range and hurt yourself. Then go to the Cure menu and use one the items your full on. This will free up space for more.

As far as I can tell, the medicinal items you get from animals like the bee hive or European Rabbit do not count for this (since they're not plants).