Isatis tinctoria
A recent review discussing herbal and alternative medicines in influenza treatment details evidence suggesting that N-acetylcysteine, elderberry, or a combination of "Eleutherococcus senticosus" and "Andrographis paniculata" may help to shorten the course of influenza infection. The article cites more limited evidence including animal or "in vitro" studies to suggest possible benefit from vitamin C, DHEA, high lactoferrin whey protein, "Echinacea" spp., "Panax quinquefolium", "Larix occidentalis" arabinogalactans, elenolic acid (a constituent of olive leaf extract), "Astragalus membranaceus", and "Isatis tinctoria" or "Isatis indigotica". Another review assessed the quality of evidence for alternative influenza treatments, it concluded that there was "no compelling evidence" that any of these treatments were effective and that the available data on these products is particularly weak, with trials in this area suffering from many shortcomings, such as being small and poorly-designed and not testing for adverse effects.