In the Arrow TV Series, Oliver Queen uses a "magic" herb from the island for instantaneous healing on many occasions. He also used it as a life saving alternative when Diggle was shot.
I am up to date on Arrow, and the herb was never named.
The comic that inspired the island flashback story was Green Arrow: Year One, and that story does not have any magic anti-poison herbs (cite: Arrow blu-ray special features).
Herbs found on Lian Yu were never named and they are only refereed by fans or even Arrow Verse wiki as Lian Yu Herbs. It was never explained how that herb works but it apparently can heal any injury including Floyd Lawton's Curare, and Sara Lance of snake venom almost instantly. Al tho some fans speculate that there is connection between Mirakuru and Lian Yu Herbs (eather Lian Yu Herbs are part of Mirakuru or that Mirakuru somehow entered soil of Lian Yu island and mutated some plants giving them healing properties), or that Lian Yu Herbs are somehow related to Lazarus Pit, it was never confirmed or denied by TV series creators. I guess now we will just have to wait for series to give us an answer, maybe even in this season since Oliver is back on Lian Yu and slaves there are gathering some strong "herbs"
Also I have not found mentioning of anything like Lian Yu Herbs in any Green Arrow comics that I've read. I also tried to google it but found no mentioning of it anywhere.
the herb could possibly be what was used in the "miracle" medication that is found on the Japanese submarine but it never really mentioned in the TV series... but the herbs are used in quite a few instances when people need "Miracle" healing that can't normally be healed spontaneously just like when Oliver, Shado, and Wilson are on the Sub and use the "Miracle" Medication to inject Wilson so that he survived being badly burned that he would have normally died from...
