Reasons for suspected connection at least at key nutrient level:
- Active ingredient in both appears to be polyphenols
- Both sources appear to be micro-organisms that appear in and around mushrooms or the soil that they are in
Kitasato Institute isolated organisms from soil samples and carried out preliminary in vitro evaluation of their bioactivity.
- Heavy research was instigated into both avermectin (ivermectin precursor) AND how chaga mushroom extract works in the mid-to-late 1960s
- Ivermectin appears to be indirectly derived from quinine which was created from "the bark of trees"; Chaga mushroom grows on the "bark of trees in northern latitudes" (avermectin+HCQ=Ivermectin theory)
Some info to get you started if you want to dig into Phytonutrients:
20APR 2022; "Clinical Evidence of the Benefits of Phytonutrients in Human Healthcare": https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9102588/
15DEC 2007; "New antioxidant polyphenols from the medicinal mushroom Inonotus obliquus (Chaga)": https://pubmed.ncbi.nlm.nih.gov/17980585/
10FEB 2011; "Ivermectin, ‘Wonder drug’ from Japan: the human use perspective": https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3043740/
Chaga info: https://en.wikipedia.org/wiki/Inonotus_obliquus
I don't think avermectin, a soil dwelling bacteria is made from quinine or its analogs.
The theory is that avermectin+HCQ = Ivermectin; However, this connection is less direct or obvious than avermectin/ivermectin sharing similar phenol properties with chaga mushroom extract. It is possible that HCQ/chloroquine/quinine/Cinchona bark shares properties with chaga mushroom (which grows in birch tree bark) extract as well, thus that possible relation.
All three seem to function in a similar way. That which functions similarly may have similar ingredients?