This is very intriguing, I'm currently growing some Leonotis nepetifolia (or maybe its another variant that's not leonuris) that seeded itself while I was away travelling for a year. It's got tons of huge leaves but the flowers are only just now starting to grow, so I'm tempted to try a handful of leaves. I tried to chew on one leaf the other day, but it was so vegetal and bitter that I didn't think it would be worth it. It'd be great to find a good use for the leaves, since I'm still waiting on some flowers and there's tons of leaf matter.
Sidenote: Anyone have any experience re the differences between buccal/oral consumption of different Leonotis varieties? I managed to get some leonuris seeds a while back but just haven't had the time to plant them so I can do a side-by-side comparison.