Gynostemma Pentaphyllum is a plant which is sometimes referred to as either 'Southern Ginseng' or 'Cheap Ginseng' as it was used as a cheap substitute for Panax Ginseng (as aside from Codonopsis Pilosula, which was used as an adulterant for Panax Ginseng to sell it at the normal price but cut costs). Surprisingly, Gynostemma has a good content of Ginsenosides that were once thought to be wholly unique to Panax Ginseng. As such, the biological effects of Gynostemma and Panax seem to be quite similar except Gynostemma may be more anti-diabetic (due to the unique Gypenosides in Gynostemma, that are not in Panax).
There are limited human studies at the moment, as most studies are attempting to delineate the large amount of Gypenosides in this herb to see which ones can be seen as the 'active' compounds. Currently, we have two human studies suggesting that a tea made from Gynostemma can be used alongside standard anti-diabetic therapy and augment the efficacy of it over time (known as adjunct therapy).
Most of its 'beneficial' effects beyond the diabetic effects (which are mediated by a possible mix of AMPK activation and PTP1B inhibition; the amount each contributes to the overall effects unknown) come from inducing antioxidant enzymes and protecting cells from oxidative damage over time. There seems to be a motif where preloading and chronic loading is very protective at low doses, and acute supplementation or rehabilitation (taking the supplement after the stressor) appears to be less effective. As such, the health effects of Gynostemma Pentaphyllum appear to be more prophylactic rather than rehabilitative or therapeutic.
This herb is also touted for youthfulness and longevity, but neither claim has been explored. Additionally, the anti-cancer effects are still in beginning stages of research but the effects appear to be very similar in many cell lines; some compound in the Gypenoside fragment may be an inducer of p53, a tumor suppressor gene, as the downstream events associated with p53 activity have been noted repeatedly (although direct kinetics between Gypenosides and p53 have not yet been investigated; this is a likely theory but not established)
Overall, this is a more anti-diabetic Panax Ginseng; the downside is that the other benefits associated with Panax Ginseng (adaptogenic, cognitive enhancing, anti-fatigue) have not yet been assessed properly with Gynostemma Pentaphyllum.