I disagree with what you're saying here, respectfully. I'd be interested to see what kind of research you are looking at. Kratom is relatively new on the block, at least as far as "Western Medicine" is concerned. We know that it has been used in its heartland, Southeast Asia for some time, mostly as a painkiller.
We know at this point that the active alkaloids within the Kratom plant are Mitragynine and its analogs. Mitragynine has been shown to be an Opioid agonist based upon research into the pharmacology of the plant.
It's telling that Kratom largely became popular as it was used by Opioid-dependent individuals as a stop-gap solution when other Opioids were unavailable and also as a withdrawal aid; Mitragynine is an Opioid of relatively mild potency, so folks tend to use it to step down from stronger Opioids.
We know that the research available to us clearly indicates that Mitragynine is an Opioid agonist. In addition, we have a tremendous amount of case studies just here on Bluelight of individuals who are Opioid-dependent using it in the above-stated applications. There have been analogs of Mitragynine sold of higher potency that Opioid-dependent individuals compare to Opioids in essentially every way.
The argument isn't really "is it an Opioid" the argument is "does it do other things aside from its Opioid agonism". It might do other things, but Occam's Razor would suggest that it's an Opioid and that's why Opioid users like it.
Of course it is always good to have a respectful discussion. Kratom is not new at all. The first good papers on it began in 1988. That is relatively new to an old man like me but ancient to most folks here.
OK, as you probably know there are 3 different colourations in leaf veins: White, Green & Red. The colouration is not due to typological differentiation but to maturation. The White has almost no 7-Hydroxymitragynine (7-OH). It's psychoactively a stimulant.The Green has perceptible 7-OH. Then the Red has the most 7-OH. If harvested at peak maturity you might find an average of 1.75% content. But, to show you what a waste Kratom concentrates & tinctures are, the greatest source of 7-OH is actually the Indolic alkaloid Mitragynine via in vitro metabolites.
At peak maturity leaves might average 60% Mitragynine, the chief alkaloid in the leaf. However, the amount converted in vitro is not quantified despite the fast & furious research taking place over the last decade. In fact manufacturers of concentrates & tinctures seem to be unaware that claiming "5X" or whatever strength of 7-OH is entirely non sensical. IF most net 7-OH is derived in vitro, how can they claim ANY strength?
It is such a crap shoot that the (US) DEA backed off of its push to Schedule Kratom & its supposed derivatives in 2016/2017. It sought Class I, i.e. the same Schedule as heroin! When DEA chemists tried to quantify its aspects they found it impossible to do so. They withdrew the entire campaign!
The point I tried to make originally was, if it is impossible to get consistent percentages of 7-OH, how could these manufacturers even know what percentages of 7-OH their products contain? IF they cannot- and they cannot- then how safe are their products? There is noone but the manufacturer paying attention. Of course their concern is financial.
There is no peer reviewed work that I am aware of that examines Kratom polytoxcity. It has been present in deaths but only as a polyexposure. There is no watchdog ensuring anything about the product(s). All there is are subjective experiences of users. Of course those can be embellished or even entirely contrived.
As I used to say here years ago, if folks want to deal with Kratom, they ought to simply source whole leaf, not concentrates or tinctures.
If you would like to look at some papers, just tell me which aspect you are interested in. There is some very interesting work.