The following cannot be said to be offerring specific clarification about gramine and overall potential adverse aspects of Arundo consumption, but, it certainly describes feeding of Arundo plant material to many types of grazing mammals.
https://www.arundo-donax.com/blog/pilot-scale-arundo-donax-plantation-for-animal-feed-2-part/My personal interpretation is that, where Arundo seems to be very unsuitable for extractions, there may be potential for it to be unique microdose option for people who would like it/find themselves to be compatible with it!
From personal experience so far, it may be that the stem is good to use.
I brought home a dry Arundo stem from California a few years ago, without knowing about Arundo, I just liked the appearance of it! Recently, I began to try chewing a very small piece of the stem bark, about 1mm in width and perhaps 1 cm in width is what I try each time (it has been about 10 times total so far), and a very welcome and powerful, also beautifully stable and seamless change in headspace happens.
That certainly reads as an extremely small dose considering the lower percentages of known active molcules of Arundo!
Yet, we do know at this point that DNA, a complex molecule, has somehow been able to produce every lifeform that has existed! By extrapolation, one could say that molecules seem to be far different from being magnetically charged inanimate objects eg. grains or crystals. There can be postulated to be some additional activity/capability that is possible for the molecular layers of existence. Thus, introducing free-to-interact molecules into our very adaptive neurochemical systems, (perhaps especially sublingually, where there may be levels of organization and activity there that have evolved speficially to receive novel molecules from our food and drink, I feel like that is far from a stretch!
) will have noticable effects whenever the molecules themselves are dynamic enough.